Quote:
Originally Posted by Thumper
Running a bit rich is not a problem. Excessively too rich will cause bogging/misfire when you twist the throttle. If it is on the edge, you won't get full normal throttle response (minor misfiring). Ideally, try one step down on the jet. If it seems more powerful and the minor bogging goes away, better. Mechanically, running rich won't hurt your engine, but the piston head, cylinder head/valve surfaces (and spark plug) will get coated with unburnt fuel which looks like a black and sooty build up. This is obvious when you pull the plug and "read" the spark plug (black dry soot). If in doubt, you can try something different, but waiting and reading the plug is going to give you the answers.
Did you save your OEM carb? It is a smoothbore YouALL PE30, and mine came with 120 main and 40 pilot jets. Jet it 125/45, reinstall it, and see how that works. It's a good carburetor. We are probably at the same altitude (below 1000 feet). On my bike, this is just slightly rich on the top end, as well as first 1/4 throttle. I shimmed the needle ~1mm (one washer) and now that the weather is warm, I don't need choke. That is at least slightly rich jetting. I think it's OK though. I also experience very slight misfire at top end, but I am not sure, so I will run it for a couple of tanks and read the plug... I might need to back off to OEM main (back to OEM 120!), or possibly remove the shim. Without some testing and time, I won't know for sure, either way. This is the first bike I got that was jet OEM nearly perfect for 600-1000 feet elevation. It is really close, and it won't hurt the bike.
Running lean is not good, but that is not what you asked!
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I’m actually at 1700 lol.
With the stock carb I was way lean. Just sitting on the bike it’s so much cooler now. The stock pilot jet may even be clogged up a bit on it, I’m not sure, but stock I couldn’t let it idle for 5 minutes without worrying the motor was going to melt, now I can idle for 20 minutes at 90* ambient temp and it’s almost cool enough to touch…almost lol.
Nah I’m not to the point where it’s drowning (like it was with a 200 main and 60 pilot
) and bogging out, just starting to get some pops at high rpm in the needle range.
That’s what made me wonder why try for perfect when I know it’s a wee bit on the rich side, but if there’s no downside to that and it keeps the motor cooler, then why not? Better to be too rich than too lean.
The Mikuni jets measure differently from keihin or dynojet but I did roughly that-I set my pilot at 40 and main at 125, assuming they would both be richer than stock. Seemed to work out pretty well although I need to really sit at 75-80% throttle under load for a while and see how it sounds. I just haven’t had the time or when I do, the energy.
Then on to the flywheel key, which I’m sure will effect jetting needs