MY HONDA’S HOT STUFF
Neil Shenton has been getting technical with his 1966 Honda CB160. Curious about engine temperatures, he bought one of those clever infrared thermometers you point at the subject. After a ride on the Honda, the magic ray showed a 10°C difference cylinder to cylinder, which persisted even after the engine had cooled a bit. This discrepancy bothered Neil, suggesting that one cylinder is working harder than the other. Ignition timing is correct and although the compression feels slightly uneven on the kickstart, the engine has been rebored recently. Neil suspects carburation, wondering if a slight float height variation is responsible. “A richer mix will presumably make that side cooler – but how do I know which cylinder is the correct temperature?” he asks, “And remind me, does rich mix indicate higher or lower float height?”
Well, low should weaken the mixture, but Neil says they’re not far out – if at all – and I don’t think float height is as critical as all that. After all, after turning off the fuel, an engine runs fine for some time before the revs rise, indicating sudden weakness, prior to cutting out. If I were Neil, I’d try a compression test. If one side really is a bit down on the other, I think that’s more likely to affect temperature – especially if there’s some combustion blow-by past the piston.
I’ve never tried one of these thermometers. I‘d rather not – if I found out how hot some of my old bangers get on a sunny day, I’d probably end up pushing them home!