carburetor or coil problem?

[WMarshy]

... I was under the impression that reducing exhaust back pressure and inlet air restriction would cause a bike with a stock setup to run lean, not rich. ...

Float height is set too rich..? What do you have them set at?

[TopCatGr58]

I agree, sounds like float heights set too rich....the engine needs more fuel cold...yours starts cold without the choke! The engine will run on less rich fuel mix as it warms up....but yours won't run/start once warmed up, again points to too rich. Your jets are actually LEAN according to the stock setup for the bike...Yamaha jetted them lean in the later years for emissions. Theorhettically you should need a few sizes richer on the mains at least, so your symptoms are curious. And yes soaking the carb bodies in the chemdip could have damaged the butterfly shaft seals...but that would also cause a lean condition??

Also, if the battery is that low then it can also cause running problems! The bike's electrical system doesn't start properly charging until around 2K+ rpm, and so idling is actually/usually discharging the battery, low battery will cause poor spark power which can also cause problems with getting it to IDLE and run! Attach a jumper booster battery to the battery at least.

T.C.