After a short ride last week went to park the scooter in the shop and it started popping. starts right up idles fine but at 1/4 throtle it starts spitting 3 inch long flames up out of the both carbs. have removed and cleaned carbs, drained and replaced fuel,checked every connection i can find. might be a bit rich but really not bad.AT this point im leaning toward timming,but could use some input .any help would be greatly appreciated I know little as of this point on how this atv gets its pulse to the coils.

 

i know my friends use to back fire alot and it was running lean. they rejeted it and it seemed to help. also sometimes if its too rich and excess gas will ignite and back fire. his 07 doesnt seem to do it no where as much.

 

If your popping through the carbs, then it sounds like you have a timing problem.