YTM 200 won't idle??

[Rocksoup]

I got my trike motor together about 2 weeks ago... runs awesome throughout the rpm range but won't idle. I've cleaned the carb, paying special attention to the pilot jet. Tried adjusting the idle mixture screw (2 full turns out +/- 1/4 turn).
IT starts easily enough. I moved the needle valve on the carb slide to various positions. Float level seems ok. What else could it be? The motor is .020 over with a wiseco 10.25 piston. I've never had that effect idle on anything else I've ever done. IF I turn the idle screw in the whole way, it will idle roughly for a bit, but eventually cut out. not sure what else to try. Any suggestions?

[Erics350x]

will it idle with the choke partly on ?

[jason 32]

adjust the cable,i have had carbs the would'nt idle with the adjusting screw in all the way,,check the slide see if the screw is even touching it
no 20 over has nothing to do with it, well from here any way:wondering lol

oh and thats the air screw i think your talking about -,there should be a slide screw as well but i dont know if it is stock ,or what bike it is

[Rocksoup]

Yeah,, the idle adjuster screw is making contact with the slide, so that's not it. I know being .020 over isn't going to effect it. The stock compression is 8.5:1. Now it's 10.25:1 That's a pretty good jump in compression. I didn't know if that could effect anything. It never has on other bikes that I've worked on.
It doesn't idle with the choke partly on either.

[mark38090]

i had a similar problem on my stock ytm 200 and it turned out to be the vent tube that runs under the tank was pinched shut...

[Erics350x]

gas cap not venting will also cause problems . also check your valve lash and timing.