250x wont run

[250xR#271]

I just got my motor back from being built, it has a high comp piston, cam, and is ported and polished, it still has the stock carb.
when I first tried to start it i figured it needed jetted way up, but I went up and the only way it would run a little was at full throttle. I went down until it would run and i also took the air box lid off. So right now I'm at a 135 main and a 35 pilot
It ran good until it got warmed up then it popped a few times and died out then to even start it I had the throttle wide open and it would run for a few seconds and die back out (like it might be flooding out). I know its in the carb. but I dont know what the problem is. I dont want to go too lean in the jetting. Do you guys think it is still too rich at 135 or do you think theres another problem

[Castor-426ex]

check the needle position...it could be wrong...sorry i cant be more descriptive than that...lol

[spliffy]

Check Your Plug , Maybe You Need A New One (Just A Guess) Also If You Got It Built By A Shop.... Ask Them What Jets You Should Be Running , They Should At Least Be Able To Give You A Starting Point , I Would Say The 135 & The 35 Pilot Is Close Though (Thats Around What I Am Using On My 250x), But Try Changing Your Pilot To A 38 & Put The Airbox Lid Back On.... Just Drill Some Holes If U Need A Little More Air.