I have a '99 yamaha 350 warrior, it was built up by Team Alba and i'm not 100% sure what upgrades they made aside from bigger jets and aftermarket exhaust.
after my last ride, the bike didn't want to start so i had to pull start it. once started it wouldn't idle. I bought a carb kit for it and cleaned it out well. i also bought a repair manual and decided to adjust the valves, since i'd had the bike for 3 years and they'd never been adjusted. I adjusted the intake to .06mm and exhaust to .16mm like the manual advised.
I can get the quad to start and after it warms up it will even idle ok, but when i rode it, it started sputtering at higher RPMs. running in first gear seemed ok, and even 2nd wasn't bad unless i reved it high in second. after shifting into third, it would start to pull but after 1/2 or 3/4 throttle it starts to sputter.
i'm suspecting the valves mainly because i can hear them clattering, where they never did before. i had never adjusted the valves before but it seems so simple, i'm not sure where i could have gone wrong. I turned the crank counter clockwise, found the "T" mark and ligned it up and then used a feeler gauge to set the gap??? why would they be making noise? Before i adjusted them, they did seem to be pretty closed.
could this be the valves, or something else? i'm also thinking that maybe the needle jet has a problem, mainly because it starts sputterign at about 50% throttle
i hope this makes sense to someone and they can help.