If the engineers at Phelon & Moore believed that their 650 M120 motorcycle needed an extra crankcase breather attached to the timing chest, I suppose they would have designed one. So why did I, with no mechanical training whatsoever, and only a rudimentary understanding of the workings of the internal combustion engine, think I knew better?
I'd been struggling with oil leaks from my 1960 Panther (first seen in RC170) for ages. After a long run at highway speeds, little dribbles of oil would start to run down the pushrod tube and from the top of the timing case at the gasket. They were never enough to be worrisome, but they were unsightly. They often drew comment from people brought up in a time of leak-free motorcycles, who mistakenly believed that any oil on the outside of an engine spelled major disaster.
Assuming that crankcase pressure was forcing oil out through the paths of least resistance, I added a breather, routed through a plastic tube to an old Guzzi one-way breather box that I'd cunningly hidden in one of the M120's tool boxes. For a while it seemed to work – until it didn't.
At the end of last year I'd been on my way home from a two-day 500 mile tour when I'd bumped into a couple of riders who wereadventure bikes, all bikes were expected to be able to do just about anything, weren't they? Let's go…
