i have a honda 250x and it starting to **** me off. when i got it it didnt run. i got it to run cuz when i got it the screw off the rocker arm fell off and chewed some stuff up. my cam had a nick and rocker arms were so warn out. i had it running for a while but it fouls my plug in seconds (carbon). i put a new piston and rings, cam, rocker arms, air filter is new (uni), new oil filter, now when that screw came off it didnt look like it the valve or springs, they look fine but i still cant tell if they r seated right or not from wear. when i put the new cam and rockers on i thought for sure it would run fine. it runs good tho, real strong, jus fouls and blows black smoke. i almost was goin to throw it down a hill when i saw black smoke when i first started it wit new rockers and cam. i think its a carb problem because when i turn the fuel air mix screw nothin happens. i can have it seated or all the way out, it wont die or adjust. i cleaned it out so many times im not good wit carbs though please help.