When I bought my Fazer last year, the biggest problem was with the fuelling / carbs. It was somehow rideable, but very far from good.When I'm saying: rebuild it to avoid suffering, then I mean suffering = what you are doing now. You try to solve your problem, but who knows what's in a 20+ years old carb?
I decided to rebuild the carbs according to my list. Man... the rubber O-rings and seals were crumbling, cracking, they were hard, because of ethanol fuel and age. Brass parts were pitted because ethanol fuel absorbs water, water corrodes everything.IMHO the only solution is using those ethanol resistant viton seals (yes, you found the proper one on the litetek site), and replace brass parts beyond acceptable. I noted which jets needs to be replaced, and ordered them, but my sligthly pitted jets are still in the carbs now. With the cleaned, resealed, synchronised carbs the bike purrs like a kitten, totally worth it. I'll replace the jets later just for the peace of mind.If you know your carbs surely OK, then you can avoid a rebuild, but the Fazer is a simple bike; only a limited number of problems are possible: wrong valve gap, leaking carb boots, bad carbs. Maybe some ignition problem, but improbable.Let us know when you'll solve your problems, I'm curious!