300ex issues. jetting or valves? need help

[nynetwo9]

So my girlfriend purchased a bone stock 98 300ex so she could ride with me at my mx track. We bought this 300 off an older guy who said it had barely no time on it. This thing is mint!!! Original tires, brakes, bearings etc... The tires have 70% tread left. Anyway, when we 1st got it, I noticed it ran like it had a dirty air filter. It seemed to have trouble starting too, once its warm it starts right up tho.

So I bought a new Uni air filter and noticed no change. Then we put a new spark plug in it and it made it a big difference. After that i found a great deal on a fmf megamax exhuast for it. It made it run a lot better but it still doesnt feel like its running 100%. I tore off the carb and took it to work and had them clean it for me(i work at a honda atv dealership). This didnt do anything either. I didnt do any jetting to it yet either. Im assuming its stock jetting. The starting issue is gettin really annoying. It seems to take forever to start. then it wont take any throttle for like 10 min. takes a while to warm up. after its warm, it fires right up.

Any ideas? is it jetting? what about adjusting the valves? Idoubt the original owner kept up with them. What jetting do you reccomend? I live in blairsville pa. 45 miles from pittsburgh.( to give u an idea on elevation)

[Tommy Warren]

go to a 128 main and if you put in an aftermarket air filter than go up to a 40 main. also check to make sure the valve clearance is .004 on all valves. p.s. If you work at a honda dealership why are you asking us???:D

[dns1764]

if the guy didnt ride it that much i would not suspect any issues with valves. it sounds more like a jetting issue

[nynetwo9]

thanks guys. yea i work at a dealership selling parts, everytime i ask the service guys about it they say it could be jetting or valves. but dont seem to know where it should be jetted to. they dont do any jetting there. they turn people away when they want jet kits installed.

[Tommy Warren]

Originally posted by nynetwo9
they turn people away when they want jet kits installed.

:huh its not rocket science

[nynetwo9]

took it to work 2nite and checked the valves, they were good. I bumped the main jet up to a 130 and the pilot to a 42. it starts a lot better now. no more hesitating and being cold blooded. thanks guys