Donny's Unauthorized Technical Guide to Harley Davidson 1936 to Present: Volume Ii: Performancing the Twin Cam

By Donny Petersen

Donny is the Winner of the 2012 International Book Awards.

Donny Petersen offers the real deal in performancing your Harley-Davidson Twin Cam. Graphics, pictures, and charts guide the reader on a sure-footed journey to a thorough H-D Twin Cam performance understanding.

Petersen's insight makes technical issues understandable even for the novice.
Donny simply explains what unfailingly works in performancing the Twin Cam.

This is the second volume of Petersen's long-awaited Donny's Unauthorized Technical Guide to Harley Davidson 1936 to Present. This twelve-volume series by the dean of motorcycle technology examines the theory, design, and practical aspects of Twin Cam performance.
Donny studied privately with Harley-Davidson engineers, having worked on Harleys for over 35 years. He founded Toronto's Heavy Duty Cycles in 1974, North America's premier motorcycle shop.

Donny has ridden hundreds of performanced Shovels, Evos, and Twin Cams across four continents doing all of his own roadside repairs. He has acquired his practical knowledge the hard way. Donny has the privilege of sharing his performance secrets the easy way. Donny will walk you through detailed performancing procedures like headwork, turbo-supercharging, nitrous, big-inch Harleys and completing simple hop-up procedures like air breathers, exhausts, and ignition modifications.

Donny Petersen feels honored to share the wealth of his motorcycle knowledge and technical expertise.

• Language: English
• Publisher: iUniverse
• Release date: Dec 30, 2008
• ISBN: 9780595627974

Donny Petersen

no back cover author bio or author picture.

Book preview

Donny’s Unauthorized

Technical Guide to Harley-Davidson,

1936-Present

Volume II: Performancing the Twin Cam

Donny Petersen

iUniverse, Inc.

New York Bloomington

Donny’s Unauthorized Technical Guide to

Harley Davidson 1936 to Present

Volume II: Performancing the Twin Cam

Copyright © 2008 by Donny Petersen

All rights reserved. No part of this book may be used or reproduced by any means, graphic, electronic, or mechanical, including photocopying, recording, taping or by any information storage retrieval system without the written permission of the publisher except in the case of brief quotations embodied in critical articles and reviews.

The views expressed in this work are solely those of the author and do not necessarily reflect the views of the publisher, and the publisher hereby disclaims any responsibility for them.

iUniverse books may be ordered through booksellers or by contacting:

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Because of the dynamic nature of the Internet, any Web addresses or links contained in this book may have changed since publication and may no longer be valid. The views expressed in this work are solely those of the author and do not necessarily reflect the views of the publisher, and the publisher hereby disclaims any responsibility for them.

ISBN: 978-0-595-52745-8 (pbk)

ISBN: 978-0-595-62797-4 (ebk)

ISBN: 978-0-595-51516-5 (cloth)

Printed in the United States of America

iUniverse rev. date: 12/23/2008

Disclaimer

This book expresses the views of I Petersen and Heavy Duty Cycles Limited (where mentioned) and are not intended in place of, or to diagnose or resolve any issue not assessed by a qualified technician. I Petersen and Heavy Duty Cycles Limited does not assume and expressly disclaims any liability with respect to the use of, or for damages resulting from the use of any information, advice, or recommendations within. We recognize that some words, model names, and designations mentioned herein are the property of the trademark holder. We use them for identification purposes only. This is not an official publication. Reference to any product, process, publication, service, or offering of any third party by trade name, manufacturer, or otherwise does not constitute or imply the endorsement or recommendation of such by I Petersen, Harley-Davidson Inc. or Harley-Davidson Motor Company or H-D Michigan, Inc. or Heavy Duty Cycles Limited.

E. & O. E. (errors and omissions excepted)

Use of the words, Andrews, Andrews Gears, Andrews Cams, Andrews Products, Aramid, ARP, Axtell, Axtell Sales, Axtell Dyno Master Performance Product’s, Band-Aid, Bendix, Brembo, Champion, Crane, Crane Cams, Crane Time Savers, Custom Chrome, Rev-Tech, Delphi, Derale, DFO, Dobeck, Doherty, Doherty Machine, MLS, Mystfree , Power Vent, Delkron, Dynojet, Edelbrock, Edelbrock Carb(s), Performer, Feuling, GESi Technology, Hayden, Hitachi, Hoover, Horsepower Inc., Ina, JIMS, JIMS Machining, JIMS Powerglide, JIMS Pro-Lite, Kehein, Kevlar, Knight Prowler, Kuryakin, Lexan, Lockhart, Loctite, Mace, Magneti Marelli, Manley, Max Flow, Mikuni, HSR Mikuni Smoothbore, Nachi, NASCAR, Pablum, Pingel, Plastocine, Procharger, Pro Vent, Prestolite, Rivera, Rivera Taper Lite, S&S, S&S Cycle, S&S Cycle, Inc., Super Stock, Spiro, STD, Sunnen, SuperFlow, SuperTrapp, Techlusion, Teflon, Thunder Jet, Tillotson, Timken, TP, TP Engineering, Trochoid, Uralite, Ultralite, VHR, Viton, Wood, Wood Carbs, various model names and designations, and OEM part numbers and derivatives of the foregoing along with trademarks and copyrights owned by the above companies or any companies owned or affiliated to the above companies whose names are listed wholly or partly are provided solely for reference, fitment, or partial fitment and application information, and there is no affiliation between the above companies or products whose names are listed wholly or partly and Heavy Duty Cycles Limited or I Petersen.

E. & O. E.

Use of the word Harley-Davidson, various model names and designations, and OEM part numbers along with trademarks and copyrights owned by Harley-Davidson, Inc. or Harley-Davidson Motor Company, H-D Michigan, Inc. or any companies owned or connected or affiliated to Harley-Davidson, Inc. or Harley-Davidson Motor Company, H-D Michigan, Inc. and derivatives of the foregoing are provided solely for reference, fitment or partial fitment and application information and there is no affiliation between Harley-Davidson, Inc. or Harley-Davidson Motor Company and companies owned or connected to them and I Petersen or Heavy Duty Cycles Limited. The words Buell, Cruise Drive, Cyclone, CVO, Disc Glide, Dyna, Electra Glide, Evolution, Evo, Fatbob(s), Fatboy, HD, H-D, Harley, Harley-Davidson, Heritage Softail, Heritage Springer, HOG, Hog, Hawg, Hugger, Lightning, Low Rider, Night Train, Road Glide, Road King, Roadster, Screamin’ Eagle, Softail, Sport Glide, Sportster, Springer Softail, Streetglide, Sturgis, Super Glide, T-Sport, Tour Pak, Tour Glide, Twin Cam, Twin Cam 88, Twin Cam 88A, Twin Cam 88B, TC88, TC88A, TC88B, Twin Cam 96, Twin Cam 96A, Twin Cam 96B, TC96, TC96A, TC96B, Ultra Classic, and Wide Glide are registered trademarks of Harley-Davidson, Inc., Milwaukee, Wisconsin, USA or Harley-Davidson Motor Company. The words: Bad Boy, Blast, Convertible, Deuce, Duo-Glide, Firebolt, Hydra-Glide, Revolution, Thunderbolt, Tri Glide, V-Fire III and V-Rod are trademarks of Harley-Davidson, Inc., Milwaukee, Wisconsin, USA, or Harley-Davidson Motor Company. The following model designations and any derivatives thereof for Harley-Davidson motorcycles are used in this book for reference only: EL, FL, FLH, FLHC, FLHF, FLHR, FLHRI, FLHRCI, FLHS, FLHT, FLHTC, FLHTCI, FLHTCU, FLHTCUI, FLHTCUTG, FLHTC, FLHX, FLST, FLSTC, FLSTCI, FLSTF, FLSTFI, FLSTN, FLSTS, FLSTSI, FLT, FLTC, FLTCU, FLTCUI, FLTR, FLTRI, FX, FXB, FXD, FXDB, FXDC, FXDG, FXDL, FXDS, FXDS-Conv., FXDWG, FXDX, FXDXT, FXE, FXEF, FXLR, FXR, FXRC, FXRD, FXRDG, FXRP, FXRS, FXRSE, FXRS-Convertible, FXRS-SP, FXRT, FXS, FXSB, FXST, FXSTB, FXSTBI, FXSTC, FXSTD, FXSTDI, FXSTI, FXSTS, FXSTSB, FXSTSI, FXWG, GE, K, KH, VRSCA, VSRC, WL, WLA, XL, XL883C, XL883R, XL1200C, XL1200S, XLCH, XLCR, XLH, XLH883, XLH1100, XLH1200, XLR, XLS, XLT, XLX, XLX-61 and XR-1000.

E. & O. E.

Contents

Chapter I The Platform for Performance

Twin Cam Radical Design Change

The Weakness of Nostalgia

The Strength of the Twin Cam

The Platform

The Achilles’s Heel of the Twin Cam

Twin Cam Performance Obstruction

Stoichiometric Air-fuel Ratio Tendonitis

Chapter II Repairing the Achilles’ Heel

The Problem: Ovaling of Bearing Holes?

The S&S Solution

The Trick: Meet Emissions Dictates with More Power

The H-D Solution

The Andrews Solution

Moment Arm Torsional Bearing Wear

Knight Prowler (Silent) Advanced Belt Drive System

Which Cylinder Is the Boss?

The Advantage Summary of Gear Drives over Timing Chains

Gear Drive Installation Instructions 1999-2006

Knight Prowler Belt Drive Installation, 1999 to Present

Hydraulic Lifter Limiter Kits

Adjusting Performance Pushrods

Chapter III H-D 110 Cubic Inch CVO

The Symptom: Blowing Rear Head Gasket

Disassembling the CVO 110: What I Found

CVO 110-Cylinders and Liner Sleeves

Why is just the Rear Head Gasket Blowing?

EPA Perfection: Stoichiometric Air Fuel Mixture

The Problem is Oil Seepage not a Compression Leak

The Causes

The Band-Aids

Redesign the CVO 110-cylinders

Solving the Tendonitis of Lean Burning Air

Performance Bonus of a Cooler Air Fuel Ratio

CVO 110 Axtell Aftermarket Cylinders

Boring and Honing Cylinders

Axtell Cylinder Installation Instructions

Engine Tuning

Break-in

Conclusion

Chapter IV Cams, Cams, Cams

Cam Lift and Valve Lift

Potential High Lift Cam Lobe Interference

Cam Duration

Valve Overlap

Lobe Centerline Angle (LCA)

Degreeing Cams

Cam Lobe Separation Angle (LSA)

Choosing a Cam

Valve Springs

Radical Cam Profiles and Engine Longevity

Chapter V Twin Cam Vibration

The Primary Cause of Internal Vibration

Survival of the Fittest: A Brief History

External Causes of Twin Cam Vibration

Vibration Specific to Rubbermount Models

Vibration Specific to Counterbalanced Softails

Internal Cause of Vibration: Flywheel Runout

The Twin Cam Flywheel (Crank) Assembly

Twin Cam Flywheel Support Bearing(s)

Twin Cam Flywheel Misalignment

Truing Flywheels

Engine Balancing

Balancing: Reciprocating and Rotating Weight

Statically Balancing Flywheel Assemblies

Dynamic Balancing

External Aftermarket Vibration Dampeners

Conclusion and Summary

Chapter VI Oil Coolers

Detonation: The Great Engine Destroyer

Octane: Engine Salvation

Heat is the Savior

Heat is the Enemy

Lugging and Detonation

Air and Liquid Cooled Engines

Turbulation Balanced with Restriction is the Key

Stoichiometric Air Fuel Ratio for Gasoline

Oil Cooler Thermostats

Oil Cooler Pressure Drop

Practical Tips: Oil Cooler Installation

Negative Vacuum Principle

Oil Pressure Drop, Wind, and Bench Flow Analysis

Jagg Oil Cooler Installation Instructions

Chapter VII Torque and Horsepower

Torque and Horsepower Relationship

Calculating Torque and Horsepower

The Interrelationship between Torque, RPM, and Gearing

Performance Requires Increases to both Torque and RPM

Compression

Compression Equals Torque

Horsepower is a Multiple of Torque and rpm

Compression Ratio vs. Cam Duration

Cam Timing Events and Cylinder Fill

Overlap, Cam Lobe Centerline Angle and Valve Closing Delays

Cylinder Pressure and Intake Valve Closing

The Exhaust System, Cylinder Fill, and Torque

Connecting Rod Ratios

Why the TC96 is faster than the TC88

Why the Ironhead XL was faster than the Big Twin Shovel

Power-to-weight and Weight-to-power Ratios

Why the Sportster is faster than a TC96

Power Formulae

Lies, Lies, and Dynos

Some Different Types of Engine Horsepower

The Worldwide Diversity of Horsepower

Chapter VIII Eliminating the Performance Obstructions

Key to Power: Head Flow

Porting and Polishing

Cutting the Valve Seat

Valve Seat Fitment

The Flow Bench

Edelbrock Performer RPM Heads

S&S Super Stock Performance Heads

Screamin’ Eagle Heads

The Exhaust System

Performance Exhausts

Power Equals Breathing

The Catalytic Converter

Exhaust Pulses

Mufflers Silencing Noise

Backpressure

Exhaust Pipe Sizing

Exhaust Effect on Fuel Delivery

Cam Overlap, Torque, Cylinder Fill, and Exhaust

Chapter IX Fuel Delivery

Ethanol Fuel

Air Filtration and Power

Velocity Stacks

Cleaning Air Filters

Performance Filters and Air Breathers

Ram Flow Induction Systems

Flow Bench Manometer Test Pressure Conversions

Carburetion

Ignitions Coordinating with Carburetion

Intelligent Spark Technology

Tuning the CV Carburetor

Spark Plug Color Tuning

Tuning the S&S Super E and G Carburetor

Tuning the Mikuni Smoothbore Carburetor

The Engine Management System

Advance, Retard Ignition Timing

EFI: Ideal Fuel Delivery

EFI Cylinder Synchronization

Sensors

Performance EFI Ignition and Fuel Modifiers

Horsepower and Torque Bike-to-Bike Consistency

Modifying the Electronic Control Module

EFI Chips, Downloads, Burns

Piggyback EFI Modifiers

Output EFI Controllers

Engine Management Software

Power Commander

Screamin’ Eagle Race Tuner and Direct Link

EFI Modifier Technology Changes Fast

Changing EFI Fuel Delivery without a Modifier

Oxygen Sensors

Chapter X The Power Train

The Engine Compensating Sprocket

Is the TC96 Gearing Too High?

The Clutch

How to Wreck a Clutch

Finding a Difficult Neutral

Speed Shifting

Performance Clutches, Springs, and Pressure Plates

Gear Ratios

Secondary Drive Gear Ratios

Final Drive Gear Ratios

Internal Transmission Gear Ratios

Performance Transmissions

The BAKER 7-Speed TC96 Transmission

Comparing Six-speed Transmissions

Evolving Rear Belts

TC96 Primary Changes

6-Speed Transmission Noise

IDS: Power Train Harmonic Pulse Dampener

6-speed Increase in Torque Transfer Capabilities

Cruise Drive Shift Clutches, Gear & Ring Dogs

The Helical Gear S&S 6-Speed

The BAKER F6F Helical Gear Conversion

Chapter XI Performancing the TC88 and TC96 Twin Cams

Two Methods to Power Gain: Cubic Inches and Air Flow

Swept Volume

Air equals Power

Screamin’ Eagle Engines

Performance Basics

One Cubic Inch Should Deliver Minimum One Horsepower

Building an Engine the Wrong Way: The Saga of R’dR

1550 EFI Engine Using .585 Lift Cams and HTCC Heads

Chapter XII Cubic Inches: Strokers and Big Bore

Piston Speed

Performance Connecting Rod to Stroke Ratios

Measuring Average or Mean Piston Speed

Piston Acceleration Speeds

Engine Maximum Rpm Calculation

Over-Square, Square and Under-Square Engines

The Power Platform

Big Bore Stroker Components

EFI Performance Components

Performance Sprocket Shaft Bearing Problem

The JIMS and S&S Engine Case Solution

2003-Present Twin Cam Engine Casing Solution

The Many Cures for Puking Oil

The 2007 H-D TC96 Scavenging Fix

124 Safe Cubic Inches

S&S 124 Big Inch Options

The Platform for Bigger Engines

History of Big Bore Engine Case Cylinder Spigots

Machining 124-inch, 4 ⅛" Engine Case Cylinder Spigots

Caveats for a Reliable Big-Inch Twin Cam Engine

Big Inch Cam Clearancing

Internal Engine Clearancing

Top End Clearance Verification

Big Inch Engine Breathing

Tuning the Motorcycle

Warranty

The Break-in Procedure

S&S Flywheel Identification

Twin Cam Big Inch Crate Engines

Chapter XIII Forced Induction

Air is King

Volumetric Efficiency

Wipe the Knowledge Slate Clean with Forced Induction

Supercharging

Roots Supercharger

Twin-screw Supercharger

Centrifugal Supercharger

Supercharger Benefits

Disadvantages of Supercharging

Detonation

Intercoolers

Cams for Superchargers

Intercooled Centrifugal Supercharger

Turbocharging

Turbocharger Cams

EFI Twin Cam Turbocharger

Choosing a Supercharger or Turbocharger

Twin Chargers

Supercharging, Turbocharging, and Nitrous Oxide

Nitrous Oxide

Dry, Wet, and Direct Port Nitrous Delivery

The Nitrous Purge Valve

The Forgotten Tuning Aid: Spark Plugs

Power Tuning Nitrous

Nitrous Jetting

Nitrous Bottle Heating for Performance

Nitrous Oxide Cams

Edelbrock Nitrous Systems for Harley-Davidson

Chapter XIV The Future

Say Goodbye to our Beloved V-Twin

Willie G. Solution for the Radiator

Generate more Power while cutting Emissions

Lighter Harley’s

The Throwaway Harley

Catalytic Converters

The Uncrashable Motorcycle

The Aftermarket Response

The S&S X-Wedge

Chapter XV Twin Cam Performance Summary

Chapter XVI 2009 Model Changes

The Twin Cam Touring Frame

Internal Engine and External Rider Cooling

TC96 Engine

TC103 Engine

CVO 110 Engine

The Transmission

Miscellaneous Touring Changes

2009 Tire and Wheel Information

Softails

Dynas

The FLHTCUTG Tri Glide Trike

Researching Service Recalls for all Years

Acronyms

Author Biography

Acknowledgements

I acknowledge my editor and publisher because they have been very much a pain in the ass.

Wow!

I thought writing The Encyclopedia of Harley-Davidson Technical Knowledge, 1936 -2008 would be easy. After all, I have been writing a minimum of one article per month since 1989; first for Canadian Biker Magazine and then for American Iron Magazine since 1992. I had the mistaken notion that I would simply sew a bunch of articles together and wind up with a work of art.

It is not that simple.

Take the title, for instance; the publisher informed me an encyclopedia started with the letter A and ended with the letter Z. He pointed that out because I was starting with the letter T, as in Twin Cam. The compromise became The Technical Guide to Harley-Davidson, 1936-2008.

The next question centered on whether Harley-Davidson knew I was writing the book. I replied that the Motor Company did not, nor did anyone else on the aftermarket side. I said that I wanted to be able to write my thoughts without marketing pressure from any company. The compromise became The Unauthorized Technical Guide of Harley-Davidson, 1936-2008.

Then the publisher wanted to know why I thought I could embark on such an ambitious venture without both of us falling flat on our faces. He asked for credentials and became impressed, especially with the fact that only the name Donny might appear on the cover of an international magazine. If the name Donny is instantly recognizable by readers and they buy the magazine because Donny is in it, that cachet should change the title one more time to Donny’s Unauthorized Technical Guide to Harley-Davidson, 1936-2008.

He did not ask a very important question.

Will the technical guide end in 2008? Of course, it will not. It will continue until the demise of current models and then the new models will evolve into separate volumes of their own. The title should end with 1936-Present, not 1936 to 2008! Oh!

Once issued with an ISBN number, the book title cannot change. The ISBN is the way books are identified by publishers, bookstores, libraries, and the like.

So, guess what. Each year of current model books will have corrections, additions, and a new chapter on the coming year.

In all twelve volumes only two models are currently available, the Twin Cam and the Sportster. The volumes on non-current models, like the Evolution or the Shovelhead, will stay pretty much the same since not much new information will be forthcoming. So, in the winter of 2008, an updated 2009 version of Volume I: The Twin Cam will arrivewith an altered main title which will now read Donny’s Unauthorized Technical Guide to Harley-Davidson, 1936-Present. It will also have a new ISBN number because the word present replaces 2008.

In addition, I will attempt to correct the typos, as well as some misinformation, notably the definitions of Octane and Detonation. These definitions will also be correct in this book, Volume II: Performancing the Twin Cam.

Confessions

All of the following mistakes are corrected in the updated in Donny’s Unauthorized Technical Guide to Harley-Davidson, 1936-Present: Volume I: The Twin Cam.

In the first printing of Volume I: The Twin Cam, I wrote, obviously in a state of sleep deprivation--how else could I have made such a stupid mistake?--that tightening a chain or belt is done at the loosest spot. Well, every mechanic knows, or should know, that a chain should adjust at the tightest spot! If adjusting at the loosest spot, the tightest spot may snap or cause rapid adverse wear. I thought of turning my foolishness into a contest about what my dumbest mistake was, the prize being of all twelve volumes, but I needed this confessional.

Furthermore the section, An Overview of the Twin Cam Fathead repeats itself twice early on in the book. Fortunately, it is not very long.

I now proof on printed pages because for some reason typos and dumb mistakes get lost on a computer screen.

I do not think I have ever easily learned a lesson in my life. Learning the hard way has one redeeming feature. I rarely make the same mistake twice, once educated, because it indelibly imprints on my psyche.

I acknowledge the patient people that made me do everything right in the ways of the publishing world because, after all, if books do not have a common format of grammar and all the other stuff, then there would be no uniformity. The readers should have some guarantee that books will follow a set of rules that provide consistency. No one ever notices this. However, if differing formats were commonplace, readers would notice constantly changing and disconcerting spellings, grammar, positioning of text, and all the rest.

I acknowledge my former girlfriend Sandra whose leaving now allows me to write in peace. I wish her good luck on finding all she wants.

The Swat Team Raid

I acknowledge the Canadian legal system that I once thought of as going easy on those charged with various offences.

I learn the hard way once again; the system is anything but that. From the predawn raid, with kicked-in doors, concussion grenades, and two swat teams; lying naked on the floor handcuffed, disoriented with a couple of cops wondering aloud why I hadn’t defecated myself from the trauma.

I kiss the ground in gratitude that Sandra was not there, for she would have risen in indignation, and been knocked down, which would have lead to my defending her with me receiving resultant rifle butts to the head and repeated electric stun gun shock tasering.

I have no children, but the raid would have traumatized kids for years to come.

For the first time in my life, I am so happy that I did not have a large pet dog. Who knows what would have happened to him?

They cannot traumatize me if I am alone. What happens to loved ones certainly would affect me in a big way.

Neighbors lining the street assume I must have done something terribly wrong to warrant the attention of an estimated seventy-five police.

Very cold jail cells prevent sleep.

Newspaper accounts sensationalize with your face front and center.

The court appearances, the sheer expense, restrictive bail conditions..., and the waiting all combine to punish before a finding of guilt or innocence.

I am lucky because I am out on bail; there are others sit in jail perhaps for over two years awaiting trial while their marriages disintegrate, pensions are lost, businesses fail, houses and possessions lost, and on it goes. The innocent have nothing once released, their lives destroyed. I now know why recidivism rates are so high in our society. How can one survive after a lengthy jail sentence without proper clothing, money, a job and emotional support?

The damage to your house is unnecessary when a phone call or knock on the door would accomplish an arrest.

Disclosure of evidence that leads to the arrest takes a year.

I knew I had done nothing wrong. Their evidence indicates that. Here I sit, waiting for a judge to rule. How long…I do not know but it may be years.

I am thankful I have friends and the money for a competent lawyer.

Now I understand why innocent people are in jail. No money equals a lousy defense in an adversarial system. A legal mind needs to pore through a pile of disclosure evidentiary paper twenty feet high.

Therefore, even innocent as I am, the punishment is still severe. On going to jail if found guilty, it is only the second last punishment of many. The last punishment is the assumption by authorities and society that you must be guilty if charged. This stigma remains forever. The assumption becomes a technicality that prevents conviction, not innocence.

The bright side is that I am able to do some writing.

In the end, this experience will have great value in again pointing me in the right direction in life from such a terrible experience.

For now, I have something that few people have. I have the knowledge of who are true and faithful friends. I also have knowledge of the bastards that pretended to be what they are not.

This alone will make the total experience worthwhile.

My case has a publication ban so I will not be able to write more until this is over.

Rest assured more information is forthcoming.

Besides how can one have an interesting life if not been kicked around once in awhile?

Now, some kind words from my old pal Lenny Creed, whose magazine, Canadian Biler Magazine gave me my first break.

25 Years with Donny and Len

When Donny asked me to write a piece, and said he would put me in his second volume, I thought how ironic as it was that 25 years ago today I was back in Toronto doing a bike show and I asked him to do the same thing!

I remember that day as if it was yesterday. When I walked into Heavy Duty Cycles in Toronto, Ontario and asked this burly biker behind the counter is Donny Petersen here the reply was depends who wants to know! Well, being a smart guy myself I introduced myself as Len Creed publisher of a motorcycle magazine called Canadian Biker and I’d like to talk to him about doing something in the magazine (I was thinking advertising but seems I had to get past this big guy first, or at least talk to a manager; someone a little more friendly!).

Then a big smile came out of this good-looking brute and said, I’m Donny and I’ve heard of your magazine. Interesting, but I don’t need any advertising if that’s what you’re thinking.

Well, I shook his hand and went into my song and dance anyways since this was to be a couple of busy days pounding on doors trying to find sales and input from the East. The more we talked, the more the wheels were turning with the idea of a feature bike or something on the shop. I had gotten something interesting but no advert yet. When our time ended, I walked away wondering if this Donny guy would ever follow through with a promise to send in a feature to me. Only days later I got a call from Donny saying he checked me out and a feature bike were in the mail to me (yes, it was mail or courier in those days and a longhand written article with a few pictures). Man, do I remember trying to decipher everything correctly from the handwriting besides doing the feature justice so we could get more of the same in the future.

That was a start of a friendship that continues today and the celebration of a new career for Donny getting published. I remember him telling me it made his day, but more importantly his mother’s day, because she always wanted him to be a teacher/writer.

Little did we know way back then that this would all come to fruition; a couple of bikers coming together with some ideas and making our dreams a reality.

Donny wrote a regular column for me, over those next five years, titled Department of Acceleration and every year we got together at bike shows, events, and rides to update each other. My biggest accomplishment with Donny (other than writing for the magazine) was to get him to use a computer. It was always old school for Don and he just could not do it on what I was paying him (or so he thought). It took about three years to get Donny to even to look at a computer, let alone learn to type again from high school--of which Don had passed with honors. It took the help of another friend of ours, Marty MacDougall, who was at that time doing the photo-shoots for the feature bikes and Marty had all the latest tech stuff. Between the two of us, we ganged up on Donny and showed him the way to even more success. He started writing for more magazines that paid better, started a teaching job at a local college, and discovered the Internet. He built a website that included many of his writings, and columns over the years followed by a host spot on Biker TV in the tech segment.

Donny is now one of the most read technical Harley writers in today’s market and I cannot tell you how proud I am of him and his accomplishments (he will probably want me to pay him for those first few years!). He is just a life long biker I like to call a friend and look forward to our next ride together because you never know what the two of us will come up with next!

Len Creed, founder of Canadian Biker Magazine and Canadianbiker.com and now Mybikespace.ca as I head into retirement just ahead of Donny The Man Petersen!

Preface

First, I am going to include a full listing of acronyms, the reduction-letters that replace unwieldy long forms in each volume, beginning with this one. I will retrofit the acronym listings to Volume I: The Twin Cam in the 2009 reprint update.

What do those damn letters stand for?

Acronyms can be very confusing to those that do not immediately recognize what the letters mean. They also prevent learning and an enjoyable read.

For example, if presented with EITMS, how is one supposed to know that it is the acronym for Engine Idle Temperature Management System, a very necessary cool-down feature in modern EFI (electronic fuel injection)?

New in this Volume II: Performancing the Twin Cam and continuing in the next ten volumes will be entertaining but educational vignettes’ called Donny’s Blasts from the Past.

Donny’s Blasts from the Past

These anecdotes will tell it the way it was. No refined and pasteurized corporate images existed back then. They were real characters, which, in part, passed on to Harley-Davidson the rich heritage the Motor Company enjoys today.

The H-D fashion of the day consisted of worn and greasy blue jeans, heavy scuffed boots, plaid shirts, and sun-faded WWII bomber jackets; dressing up meant putting on a black long-sleeved shirt.

The vignettes are not always complimentary but they are as true as memory will serve. Of course, storytellers add their own twists.

Mouldy and the Land Speed Record

I will revisit Mouldy, the irascible local dealer who attempted to badger Fast Eddie, his head mechanic, into attempting a land speed record on a Knucklehead in the 1940s.

The wind was too strong, causing one hapless rider on Eddie’s Knuckle to lose a leg.

Pissed, Eddie hopped on a Snortin’ Norton and set the record, not much good for a Harley dealership to crow about their products.

It was a man’s world, where the dealership personalities--Mouldy, Fast Eddie, Shy Ron, and sometimes Fats--would hop on their rigid frame Knucks, Pans, and the odd Flathead 80 after Saturday closing to ride five-hundred miles and camp out before returning to work Monday morning.

Shovelhead Warranty Blues

In another blast from the past, Donny will tell about Teddy, the circa-1980 service manager at another H-D dealership, frustrated with the volume of Shovelhead warranty claims.

Teddy set up a betting pool for the mechanics and himself. They would all gather round with each Shovelhead delivery and bet if the new Harley would make it out of the parking lot before breaking down.

Readers should not interpret Donny’s Blasts from the Past as put-downs or other types of negativity but as glimpses at the way, it was. Those days were rough and ready, and they were fun. Political correctness did not exist on any level.

The era’s bikers were sexist, as was society in general. Donny’s Blasts from the Past may contain sexist commentary. However, this commentary’s design is to suggest the flavor of days past.

I may use some words such as Limey bike, which I guess might interpret by some as racism directed against the English. There is no intent as such. A Limey bike simply meant a BSA, Triumph, Matchless, or Norton motorcycle to distinguish them from the only other two games in town, Harley and Indian. Riders, back in the day very much respected and loved the Limeys.

Donny’s Blasts from the Past will serve to demonstrate just how far Harley-Davidson has evolved. They will show just how good the Twin Cam is relative to what has gone before.

Harley gained popularity because of the personality quirks of both the bikes and the people around them. In a homogeneous world with each big-box store identical to the others, present and future vignettes will fall by the wayside.

Donny’s Unauthorized Technical Guide to Harley-Davidson, 1936 to Present will comprise of the twelve volumes listed below. A brief synopsis follows for the reader’s perusal.

I.               The Twin Cam

II.              Performancing the Twin Cam

III.            The Evolution: 1984 to 1999

IV.             Performancing the Evolution

V.              The Sportster: 1952 to Present

VI.            How It All Works

VII.           Shovelheads: 1966 to 1984

VIII.         Lubrication

IX.            The H-D Technical Encyclopedia

X.              Panheads, Knuckleheads, and Flatheads: 1929 to 1973

XI.            Tech Tips

XII            Living the Dream

Each volume will describe, discuss, and analyze a different technical subject within the world of Harley-Davidson except Living the Dream, which will be about my riding exotic locales and the Rode-Mode survival tips I learned the hard way.

Volume I: The Twin Cam lays the groundwork for all that follows in Donny’s Unauthorized Technical Guide to Harley-Davidson, 1936 to Present. I view the Twin Cam as a transitional model into the future as the Factory must deal with ever-increasing EPA dictates especially in 2010 and beyond. Let us not forget the influences of the California Air Resources Board (CARB), which many times may predate EPA guidelines.

I think the V-Rod is the Twin Cam’s design future.

Volume II: Performancing the Twin Cam is a dynamic introduction to the quest for speed.

The Twin Cam is the best platform for performancing in the world of Harley.

Carburetors, fuel injection, cams, headwork, strokers, big-bore, supercharging, turbocharging, nitrous oxide, and much more are all hot topics for discussion.

A comprehensive chapter will also discuss the problematic CVO 110 engine.

I will redesign this engine, giving it the greatness it aspires to.

A chapter on vibration will discuss the inherent dangers beyond rider discomfort to support bearings as well as the rest of the motorcycle from performance and longevity perspectives.

Vibration and performance do not mix. I will talk about how to eliminate many types of vibration and how to minimize the rest through truing flywheel assemblies to balancing techniques.

Then I will take the reader through building a very reliable 124-cubic-inch engine using stock Twin Cam engine cases, a feat no previous H-D engine has managed to perform.

Volume III: The Evolution: 1984 to 1999 is the bike that many credit with saving Harley-Davidson from bankruptcy. Why did it become the chosen one? After all, there was a more progressive and practical bike in the works. However, Harley-Davidson is not about practicality.

How did H-D become the darling of American capitalism?

I will explore the Evolution from different perspectives, explaining why it is so much faster and more reliable than its Shovelhead predecessor is. However, there is a lot wrong with the Evo that loyal riders love to overlook. I will get my hands dirty demonstrating the many foibles of the Evo.

Volume IV: Performancing the Evolution will describe the hop-ups available for the fastest of the Harley Big Twins up until 1999. It is easy to make the Evo faster within the limitations of the engine and retain reliability. I will explain how and show you what to do, and perhaps more importantly, what not to do.

Volume V: The Sportster: 1952 to Present will begin with Flathead K models and lead into the birth of the modern Milwaukee Vibrator, the 1957 overhead-valve Sportster. The Sportster lost its vibrator status in 2004, entering a new era of touring capability. I will chronicle the Sportsters many mechanical changes over the years.

The historically ignorant and sexist derisively relegate the Sportster to girl’s bike status. Originally, a man’s bike, the Sportster dominated racing as well as the hardcore outlaw lifestyle that all modern riding clubs like HOG are based on. Consequently, it is the most customized Harley of all time.

Performancing this ground-pounder will be a hot section of the book.

I will then explain the future and all the changes that will occur to meet the 2010 and later Environmental Protection Agency (EPA) emissions restraints. There will be big changes in the Sportster to meet compliance that began with electronic fuel injection for all models in 2007.

Surely, the Sportster also faces a major redesign in the very near future. Perhaps the Buell 1125R is the harbinger of change. Never mind perhaps! It will be the future of the Sportster.

Volume VI: How It All Works, will be a techie gearhead’s dream. I will explain the component parts of the engine and subsequent Powertrain from valve springs to sprockets, examining their individual functions and interrelationships.

A total understanding of the many V-Twin’s, the Flathead, Knuck, Pan, Shovel, Evo, Twin Cam, K-model, and the Ironhead plus Evo Sportster engines in addition to the beginnings of the V-Rod will evolve in the reader’s mind. With this understanding, analysis will follow and thus the ability to diagnose.

Volume VII: Shovelheads: 1966 to 1984 will discuss their development from the Panhead. The Shovel lost our affection with the advent of its more reliable successor, the Evolution. The Shovelhead is back with a vengeance feeding the bobber boom the custom industry is currently enjoying. The Shovel has become one cool bike.

Volume VIII: Lubrication is the all-time favorite subject of those that discuss their bikes and mechanics.

Which brand oil is the best? The half-truths, marketing claims, and mythology surrounding oil form a maze that few penetrate. I am going to remove the hype and give the real deal. Which oil will win? The combatants will be out of the ground fossil oil versus fabricated synthetics.

Myth will separate from fact, perhaps giving the reader his first unbiased look at this intriguing subject.

I will then go in depth about Harley’s marking their spot. Why do traditional oil leaks occur? How do we fix them? Why does your Harley puke oil out the breather? I will explain what is wrong and why and then explain the fixes.

Volume IX: The H-D Technical Encyclopedia will be a calculation reference bible.

There will be a comprehensive section on engine formulae that will cover calculations of every aspect of Harley-Davidson mechanics and performance. This will follow with explanations on how to make them work for you. The book will discuss such topics as taking everyday practical engine formulae like calculating compression ratios, explaining the math, and then applying the results to bump an engine’s compression.

I will also discuss a myriad of interesting topics like calculating cubic-inch displacements, transmission gear ratios, and final drive ratios.

The reader will learn how--just like the experts--to modify his particular bike’s specifications, altering them to tailor his specific needs and wants.

Volume X: Panheads, Knuckleheads, and Flatheads: 1929 to 1973 will chronicle the development of the Flatheads from 1929 to the demise of the pie-wagon trike in 1973.

Yeah, I know, I screwed up the title of the book. It should read 1929 to Present not 1936 to Present. My knuckle brain was thinking of the Knucklehead, which did begin in 1936. Some really interesting stuff happened between 1929 and 1936 and I will cover it all.

Next, I’ll discuss the first hemi head Harley, the legendary cast-iron Knucklehead built from 1936 to 1947.

This intriguing volume will round out with an exploration of the beloved 1948-65 Panhead.

To quote the sexist vernacular of the day, It takes a man to ride a Pan.

Volume XI: Tech Tips will offer hundreds of practical tips on Harley-Davidson mechanics, short cuts, roadside repairs, and general information that will be intriguing for gear heads and casual readers alike.

One of yesteryears tips concerns a roadside fix using Comet cleanser to prevent engines from smoking oil out the exhaust. Blowing this fine abrasive into the carburetor throat reseats worn-out piston rings. This treatment stops smoke emanating from the exhaust pipes and, more importantly, prevents the spark plug from oil fouling, leaving the rider at the side of the road.

This volume will read like Confucius’s sayings.

Volume XII: Living the Dream will contain roadside technical advice interspersed with my biking adventures. Sprinkled throughout will be Rode-Mode practical guidance that every high-miler learns the hard way, such as surviving impacts at speed with dogs as well as bears, cows, deer, moose, and a flock of Canadian geese. My riding friends and I have encountered them all.

Living the Dream will chronicle my rides around the world, from crisscrossing Europe and North America, to riding Central America and Brazil.

The riveting circular ride around South Africa to God’s Window is in a most beautiful and friendly place.

However, there are ten different ways to die each day.

Introduction

These twelve volumes comprising Donny’s Unauthorized Technical Guide to Harley-Davidson, 1936 to Present is a culmination of a life’s work that is not yet complete.

Firstly, the volumes that discuss Harley-Davidson’s that are still in production will not end with the year 2008 or 2009 or 2010. These volumes will update every year. There will be a banner across the covers to denote 2010, 2011 and on it goes until Harley-Davidson ceases production of a particular model.

Therefore Volume I: The Twin Cam will reflect updates beginning in 2009. I will update Volume II: Performancing the Twin Cam as necessary. The year of updates will be on a banner on the cover. Volume III: The Sportster 1952 to Present will begin updated versions in 2010. Knowing me the way I do, I can see myself adding to all volumes every year as I am on a constant learning curve that never seems to end.

I realize constantly how little I really know relative to how much I still have to learn.

When the Motor Company replaces the Twin Cam or the Sportster with new models, there will be a thirteenth and fourteenth volume for these new Harley-Davidson’s. I also plan a future additional volume on the V-Rod as I think Harley-Davidson will incorporate its design or major parts of its design into the motorcycle that will replace the Twin Cam.

I view the Twin Cam as a transitional model into the future as the Factory must deal with ever-increasing EPA dictates especially in 2010 and beyond. Let us not forget the influences of the California Air Resources Board (CARB), which many times may predate EPA guidelines.

Surely, the Sportster also faces a major redesign in the very near future. Perhaps the Buell 1125R is the harbinger of change. Never mind perhaps! It is the future of the Sportster.

It follows that I think the V-Rod is the Twin Cam’s design future.

 Chapter I

The Platform for Performance

Mechanically, the Best Engine Since 1903

Much of the Twin Cam engine is a bulletproof platform for the future of Harley-Davidson with this genre engine. Designed with durability and reliability in mind, the engineers were expecting a minimum of one hundred thousand miles before a rebuild.

Excepting the 1999-2006 problematic timing chest components, which the performance mechanic easily fixes, the longevity expectations are likely understated.

Many times, my writing necessarily focuses on the problems and fixes associated with Harley-Davidson motorcycles. This may create negativity after awhile, simply because the reader may lose sight of the wonderful aspects of the Twin Cam engine relative to what has gone before.

Was the Evo a Great Engine?

Sure, the 1984-1999 V2 Evolution was a great engine, relatively speaking. Perhaps it was not so great when one becomes familiar with the various foibles over a highly successful sixteen years of use.

The Harley rider is still very forgiving of any problems. Many seem to suffer memory lapses over warranty issues like engine casing porosity and cracking, and let us not forget those forever-leaking base gaskets. I attribute these wonderful memories of Evolutions to the positive aspects of the engine and comparable bikes of the time. Many of these riders were fresh off their beloved Shovelheads.

The Evo was very much faster than what went before because of the D-shaped combustion chambers, the introduction of the squish band and flattop pistons. For the first time, the air-fuel mixed better, making the Evo so much faster than the inefficient hemi head 1966-1984 Shovelheads.

Evo reliability also became a legend in its own time, as the V2’s reputation was very deserving relative to the Shovel.

If the reader thinks I am kidding, let me relate a Donny’s Blasts from the Past true story circa 1980. A large local multi-line dealership could only laugh in embarrassment at the breakdown rate of the Shovelhead when comparing to their Japanese products even though these bikes outsold H-D by about ten to one.

Donny and H-D Design Engineer with Prototype Twin Cam

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I am standing with Bob Koby Kobylarz, the chief engineer of the powertrain division of Harley-Davidson Motor Company behind a prototype Twin Cam engine in March 1998. The revealing of this engine by Harley-Davidson born from the ultra-secret P22 project to Buzz Kanter, Chris Maida, publisher and editor respectively of American Iron Magazine and myself was one of the most exciting moments of my mechanical life. We signed secrecy agreements with the Motor Company not to reveal what we had seen until half a year later. Koby and I are standing just outside the Harley-Davidson Archives in the old six-story building at 3700 Juneau Avenue in Milwaukee Wisconsin.

© American Iron Magazine, reprinted with permission of (www.AIMag.com)

Betting on Shovelhead Warranty Claim Volume

My buddy Ted, the service manager, had four stacks of warranty files on his desk at any given time. The Honda, Suzuki, and Yamaha piles were each about ⅜ thick. The Harley-Davidson Shovelhead pile was always 6 thick and some days so high it was in danger of falling over.

Teddy and the mechanics had a pool set up to bet on how far the newly delivered Shovels would go before the writing of the first warranty claim. Many bikes did not make it out of the parking lot before Ted, in resignation, wrote the first claim.

Evo reliability was astonishing in light of the only comparisons available like its predecessor the Shovelhead.

I am a mechanic that has traversed the Shovelhead, Evolution, and Twin Cam years. The increases in reliability of the Evo over the Shovel and now the Twin Cam over the Evo are astounding.

Harley-Davidson has made huge strides in this area. Some individual components in the Twin Cam engine will last many multiples of the magic one hundred thousand mile figures. This is a telling statement in an age of planned obsolescence when vehicles and parts have a built-in life expectancy.

Bulletproof Parts

The 1999-2002 engine casings that utilize the opposed and tapered Timken bearing sets to support the sprocket shaft in the left casing successfully since 1956 are a superlative design.

In my opinion, these 360 specially formulated proprietary alloy casings, with care, will be serviceable for a half-million miles and beyond. For further testament in Chapter XII: Cubic: Strokers and Big-bore I will build a very reliable behemoth 124-cubic-inch Twin Cam using stock Twin Cam engine casings!

The 2003 and later casings will not be as fortunate since the engineers have eliminated the very reliable sprocket shaft Timken bearing sets in favor of a single roller bearing. The year 2000 and later Softail engine right-side pinion shaft roller bearing has supplanted the Timken bearings on all 2003 and later Twin Cam engines.

I do not feel this type of bearing that works wonderfully with the up-down stresses imposed in the right casing will be able to withstand the extra rigors resulting from the throbbing sideway power pulses of the transferring power stroke down the powertrain to where the rubber contacts the asphalt. The Timken bearing sets are more tolerant of crankshaft flexing at high rpm. Interestingly, both current manufacturers of aftermarket Alpha Twin Cam casings, S&S Cycles (www.sscycle.com), and JIMS USA (www.jimsusa.com), use the Timken bearing setup instead of the roller bearing on the sprocket side for all year applications.

JIMS USA also makes Beta Softail Twin Cam cases that use the sprocket shaft Timken bearing sets for all years also.

However, if using 2003 and later stock engine cases for a performance application that uses a roller bearing on the sprocket shaft does not bother you, I will describe the various ways to overcome this potentially bad performancing situation again in Volume XII: Cubic Inches: Strokers and Big-bore.

Twin Cam engine case manufacturing only requires clamping five times for complete machining. Clamping distorts the alloy, which can cause machining distortions as the alloy bounces back to its former shape before clamping. Less clamping means a superior product. In comparison, the Evo cases require clamping thirty-two times.

The permanent mold cylinder heads using 242-alloys is also outstanding in their quality construction from a longevity point of view.

An efficient Twin Cam head design using a bathtub combustion chamber on the inside accompanies a 60% increase in finning on the outside for superior heat exchange into the atmosphere. I feel these heads will be around many decades from now, rebuildable for following generations of riders wanting original stock parts.

However, the respective heads do not flow enough air for a stock TC88 1450cc or for the TC96 1584cc engine. In fact, they flow less air than a set of smaller 1340cc Evolution heads. While the TC96 heads have improved flow over the TC88 heads, it is still not enough for the performance-minded rider. This airflow concern also need not bother the reader, as I will elaborate on this issue later in this chapter and will remove the impediments to airflow in Chapter VIII: Eliminating the Performance Obstruction.

The barrels, also known as cylinders, are shorter due to the smaller stroke of 4.000 from 1999-2006 and 4 ⅜ in 2007 and later Twin Cams and combine with a higher deck height on the engine crankcases. The deck height is where the barrels mount onto the engine cases.

Shovelheads from 1978-84 and Evos from 1984-99 used longer cylinders because of an elongated 4 ¼ stroke and lower cylinder decks on the crankcases. The Twin Cam cylinders are fatter due to the massive 3 ¾ bore and the increased fin area. The cylinder sleeves that house the pistons are thick (.247 compared to the Evo’s .173). This ¼"-thick sleeve liner provides stability for the piston as it changes thrust axis particularly at the bottom of the stroke.

The theme of rigidity in this platform engine comes into play to provide stability for component parts. This is due in part to the thickness of the liner but also because of the new spiny lock iron sleeve cast into the high-pressure, die-cast cylinder.

Mounting the engine and transmission together is another superlative move on the part of the Motor Company. This provides much rigidity to withstand the torques twisting forces traveling down the powertrain. No longer does the primary system need to function as a support, although it still lends its unifying force.

Let us get back to the cylinders and their mating black Teflon-coated hypereutectic aluminum pistons. Oil-cooling jets relieve about 500 F from the piston crowns. Hypereutectic is a cast piston with greater than 12% silicon content. The silicon crystallization prevents heat transfer to the more vulnerable piston skirt thrust areas, allowing them to run cooler. They are the strongest of any pistons previously used by the Motor Company, are most resistant to piston-to-wall scuffing, and least likely to seize up in spite of the very close fitment to cylinder wall.

I broke in both my 2006 TC88 FLHXI and my 2007 TC96 FLHXI at 55-75 mph and 60-80 mph respectively in cold weather. I disassembled and performanced both bikes soon after the break-in period. The piston ceramic coatings had nary a mark on them. When Harley-Davidson does it right, H-D does not fool around!

The combination of pistons and cylinders with the possibility of five over-bores will ensure longevity for over five hundred thousand miles or more, maybe even double if religiously cared for.

Piston wristpins have always been a durable engine part. The Twin Cam wristpin is big, and I mean big, with a correspondingly large wristpin bushing in the matching connecting rod that is meaty enough for the biggest engine. An Evo wristpin is .792 thick while the Twin Cam’s is a whopping .927 in diameter.

The right case support bearing for the pinion side of the flywheel assembly is a huge roller bearing about 3 ½" in diameter, about double that of the relatively skinny needle roller bearing in the Evo that sits on a beefy pinion shaft forged as part of the right-side flywheel.

The Twin Cam pinion shaft is .400" thicker than its counterpart Evo at the pinion bearing location is.

The three-oiling-hole crankpin is muscular and .420" thicker than the diameter of the now skinny single-oiling-hole pin used in the Evo.

All engine covers like the nosecone or timing chest, the split two-piece rockers wafers, and the guide block covers are just that…covers and will exceed one hundred thousand-plus miles of leak-free usage. No more will these covers act as load-bearing supports for other engine parts as they have in all engines before 1999.

The connecting rods are the biggest and strongest ever used by the Factory. In fact, they are bigger than aftermarket con rod sets designed for the big inchers.

The theme of size continues with the captured three sets of eighteen needle rollers in copper-coated cages, which help break-in procedures, provide durability, and offer easy-wear spot identification. Captured is an engineering term to describe the type of bearing cage, which supports each of the eighteen bearings per cage around all sides.

The cylindrical roller bearings are bigger than the Evo’s or the Shovel’s. There are three more bottom end bearings than in the Evos and the late Shovels. They are the same diameter but longer in length.

I could go on, but the reader now understands what a platform for power this engine base really is.

In my opinion, it is unusual for a modern manufacturer to make parts as durable, with as much built-in longevity as Harley-Davidson has with both the Twin Cam TC88 and the TC96.

The ongoing theme of rigidity ensures that the Twin Cam will not only be the best- handling Big Twin at speed and in adverse handling situations but will transfer horsepower through the powertrain without the torsional twisting so common with previous Harley-Davidson’s.

For extensive information on the technical aspects of the stock Twin Cam TC88 engine see Volume I: The Twin Cam, Chapter I: March 1998: Introduction of the Twin Cam and for the TC96 engine see Chapter VIII: The 2007 TC96 Engine also in Volume I: The Twin Cam.

Stress versus Parts Longevity

Individual simple parts from the 1999-2002 huge rubber-mount pinion ball bearing to more complex pieces like the head castings and the superb engine casings do not appear to have built-in obsolescence.

Properly trued flywheel assemblies, at the Factory to one-thousandths of an inch (.001"), or less will surpass the 100,000-mile marker easily. Those that are out-of-whack anywhere from three or four-thousandths of an inch and up will damage mating components like the oil pump and the cam support plate, eliminating the particular engines they are fitted in from the vaunted high-miler club.

Other weaker parts, such as the 1999-2006 timing chest components and 2003 and later sprocket shaft bearing, will be hard pressed to keep up with the high-miler parts, some of which I have already listed.

The Softail 2000 and later pinion bearing is still very big but smaller than the 1999-2002 rubber-mount pinion-side ball bearing.

The jury is still out on the timing chest changes instituted with the 2006 Dyna and carried over into all 2007 and later Big Twins. The changes for the most part look positive, but time and miles will be the evaluator.

Engine Stress

Why would the same pinion bearing be so reliable in this situation but not so durable in the other, as the sprocket shaft bearing? After all, this bearing supports the flywheels at either end on their shafts as they pass through the engine casings into other compartments.

Stress is the short answer.

On the pinion shaft, the ball bearing simply and effectively allows the shaft to rotate in its center. The only stressors are perpendicular to the rollers.

On the sprocket shaft, also known as the power shaft, pulsating power surges thrust out, driving the primary sprockets and chain, turning the transmission while the clutch engages, and, finally, powering the final drive, turning the wheel.

Different stresses require different types of bearings.

Comparing Twin Cam Flywheel Support Bearings

missing image file

Pictured from top to bottom is an H-D 9028 tapered Timken sprocket-shaft-bearing kit in use from 1999 to 2002 in both Alpha Dyna and touring models and Beta Softail models to support the flywheel sprocket shaft in the left-side engine casing. The next single roller bearing is H-D 24623-99, H-D 24623-99A, and H-D 24623-99B pinion bearing used from 1999 to 2002 on Alpha models only to support the pinion shaft in the right-side engine casing. The third bearing is the same early pinion bearing but did not self-destruct, which would be highly unusual because of its sheer size and strength married with proper function. I destroyed it to show the reader the component parts. Lastly, on the far right, H-D 24604-00, H-D 24604-00A, H-D 24604-00B, H-D 24604-00C, and H-D 24604-00D sprocket shaft bearing and pinion shaft bearing in use on all B models from 2000 to 2006. This roller bearing is also adapted for use on all Twin Cam A models from 2003 to 2006 on both pinion and sprocket shaft sides of the flywheels. The 9028 Timken inward-facing tapered bearing kit is comprised of two tapered races fitted with two tapered roller bearings and separated by a precise spacer-shim that determines flywheel endplay inside the engine cases. There sixteen different-sized spacer-shims vary in size from .0895 to.1195 in successive gradients of 20-thousandths of an inch. Different sizes enable a mechanic to choose his own end spacing. For example, a stroker will require more spacing as more heat generates, possibly causing parts to expand more. After installation of the bearings and races, a thicker race may be required to increase endplay, or a thinner one may be necessary to decrease flywheel side movement inside the engine casings. The races press into the sprocket shaft hole in the center of the left-side engine casing with the tapers facing each other. The inside tapered Timken roller bearing presses onto the sprocket shaft with the taper facing the engine casing. The flywheel set installs into the casing. The spacer fits loosely on the sprocket shaft and installs from the outside of the casing. Then the other tapered roller bearing presses onto the sprocket shaft and into the casing from the outside. The spacer separates the two bearings, determining endplay for the flywheel set. This bearing kit in slightly different variations has been in successful use from 1956 to 2002. The discontinuation of the tapered Timken bearing kits is a huge disappointment to the performance mechanic. These bearing kits never presented any problems and proved to be very reliable and durable. In my opinion, the H-D 24604-00 roller bearings that replaced the tapered Timken kits on the A models in 2003 and the B models from their inception in 2000 are well suited to withstand up-and-down forces. This is why they work so well on the right pinion side of the engine, where there is no side thrust forces. However, on the left sprocket power side of the engine there is powerful and pulsating side thrusting outward forces. I feel this type of roller bearing is ill equipped to handle this kind of situation over a long time-period, especially in performanced engines. I think the reason the bearing is so large is to compensate for these side-thrusting forces. So, why did the Factory change to these roller-type bearings? Ease of installation, less parts involved and less expense come to mind.

Wrong Bearing Use

In the first year of the Twin Cam, two identical ball bearings were in use to support the outboard cam end journals in the cam support plate. The rear one self-destructed while the front one, mere inches away, rolls on effortlessly. Different stresses allowed one cam bearing to enjoy the ride while the other disintegrated.

Simply replacing the ball bearing as the rear cam support in late 2000 with a roller bearing solved the problem.

In my opinion, the rear-cam-journal support, Ina bearings used from 1999 to 2006, excepting the 2006 Dyna, are another inappropriately used bearing. We see damage to them all the time at Heavy Duty Cycles. We always use B-148 Torrington bearings to replace them. Both Crane and S&S recommend this also. They are both needle-type caged roller bearings, but the Inas are smaller with supports to assist them in rolling square and true. The Torrington rollers are larger with more rolling area. In the 2006 Dynas and all 2007 and later Twin Cams, H-D still uses Ina bearings but has increased their inner diameters .125, from .875 to a full 1.000". I am sure these will be more durable than what went before, but I highly recommend replacing them with the equivalent B-168 Torrington bearings.

However, H-D has used the same type of Ina bearings throughout its five-speed transmissions since 1980. In this situation, they work wonderfully and very rarely need replacement even on transmissions twenty-nine years old! Of course, we replace them during rebuilds on general principles, but they are extremely reliable and durable in the transmissions.

Different stresses for different bearings explain all.

Twin Cam Radical Design Change

For the most part, Harley-Davidson has obviously overengineered many components in the Twin Cam engine.

The 88 cubic inch (1450cc) Twin Cam is the most radical Big Twin design evolution to occur in six decades since the historic inception of the first complete overhead valve Harley engine, the 1936 EL 61-cubic-inch (1000cc) Knucklehead.

The Evolution V2 (1984-99), engine signified the birth of the modern Harley-Davidson superseding the dinosaur technology of the last hemi, the Shovelhead (1966-84).

The Evo moved away from inefficient hemispherical combustion chambers and matching round-dome pistons to a modern squish combustion chamber with a mating flattop piston.

The V2 established huge gains in reliability and quality of construction over what went before. It was also the fastest Harley-Davidson to date. I have ridden them at high speed over long distances with nary a complaint. The Evolution