The motor in question has turned out better than I could have hoped for so I turned my attention to the cylinder. Lifting the cylinder off the pistons they’re all quite nice, just with a soft, flaky carbon coating; to me this indicates excessive richness or oil passing the rings or, of course, a mix of both.
I didn’t have a head with the motor but examination of the rings helps to explain the position: they’re knackered. And by that I mean the ring end gaps are way too big at almost one millimetre. The bores are pretty good, though. I give them the lightest hone with my solid stone hone and I can see that apart from a few minor scuffs all is well. But checking the ring cost really blew my wig off: over £200 for a set of hoops! I remember the old story about Honda’s start in the UK market. Apparently, they didn’t earn a cent from bike sales for the first 10 years but they did fairly well from the sale of spares. I
