K it idles fine even give it a quarter throttle than it sputters and backfires i checked the plug and it is dry with a tad bit of white on the edge.......Does this mean it is running lean my main jet is a 145 which is stok and i have a supertrapp pipe on it. wat should i do???

Thanks, John

 

That wouldn't be your problem, it's probably a little lean with the stock jet on the aftermarket pipe, but not so much that it wouldn't run. All you'd notice is some popping on deceleration, and that it would be running hotter than normal. You have to be real lean to keep it from revving up at all.

 

Do you have an open airbox or aftermarket airfilter by any chance also?..I would start with getting a bigger jet since that will help a little bit and I would also adjust the adjuster screw on the bottom of the carb and see if that makes a difference.

 

well it ran fine with tht jet, i did djust the air screw and nothing, i also tried the parking brake, reverse ground, it idles perfect but i kno for shure now its the valves because i could hear them leaking when i turned the motor over by hadn the other day, i also did a compression test by puttin my finger over the spark plug hole and i could hold my finger which from wat im told means i have bad compression and since i can hear them leaking on each stroke i kno wtht the problem i am 99 percent shure cause also the timing is dead on too ty for ur help its all appreciated, John

 

its the valves, i pulled the head tonight, i can stick paper thru the port and cylinder head so thanks for all the help was very appreciated..... John

 

my raptor did the same thing it was the parking brake, try that it should work