by bgsengine » Thu Sep 21, 2023 6:16 pm
or, alternatively, thermal expansion causing a leak (which was compensated for in cold adjustment) to stop leaking.... It'd be hard to tell which one, I might consider checking exhaust temperatures (if you got a thermometer to do that) or, at start-up use the ol' carb cleaner spray around suspect areas trick, if no leaks then, try it again when the engine gets hot and warmed up. I'd normally suspect carburetion assuming everything else is in spec after rebuild (leakdown test cold vs hot, which is also difficult to achieve effectively) and if you have a spare coil handy, try that (could be an intermittent misfire that you could only pick up on a DSO, it'd happen too fast to be visible, and not often enough to cause a real performance issue) and lastly the problem might go away after some run time (new parts broken in, etc.) I remember having that problem show up every so often, but more frequently on winter engines (logsplitters, snowblowers) - we rarely ever serviced things like mini-bikes or whatnot with centrifugal clutches so I don't have a lot of experience that way, our usual solution was to dial down cold idle (immediately after start-up) to just enough for it to stay running (and make sure it will accelerate on snap throttle) and whatever the idle was when it was hot was not normally a big issue (Since most stuff we serviced with those engines typically only ever operated at full throttle anyhow) but I was always curious as to why they did that, but had so few of them I never really had a chance to experiment with them (most were paying jobs that the incentive was get it to run for its purpose and ship it, if it idled a tad fast , no biggie)
How poor are they who have not patience. What wound did ever heal, but by degrees? - Iago (Othello Act II, Scene 3)