I have just rebuilt the top end of an 88 YFM200 that was given to me (soked like an old train)... and I completely cleaned out the carb (it was really dirty and the breather tube was plugged). now the only way it wil start is with allot of starter fluid.. once started I have to keep working the throttle to get it going.. once above idle it seems to run ok and I can drive it around but as soon as I stop it dies unless I work the throttle... any suggestions... is it spark issues at idle or carb issues... I turned the slide screw in all the way and no help, I adjusted the needle jet in and out (book says 1~2 turns) ut no help.

 

it kinda sounds like a timing problem to me have you checked the timing