On my 86 lt 250r, my engine runs great when ideling, top end, bottom end, but i seem to have trouble when i hit a bump, and its a quick jolt to the quad, it seems to dog down for just a split second when i try to get on the gas. this has pist me off alot recently, i have my own mx track and when i hit the steep jumps it seems when i need to gas it in the air, theres absolutely no power whatsoever in the air and have came down nose low many times and has scared the hell out of me. what sounds like the problem im having? clogged gas line or what? maybe eletrical problem, im not sure where to start looking? some advice would greatly be appreciated. thanks

oh, and im not running any engine mods either, stock carb, bored over .65, racing fuel mixture... and was told by many people it wasnt the problem, my quad runs alot cleaner now, no more black crap all over the engine and pipe.

 

My quadsport did that. Get a PC racing carb vent system and It'll run right again.

 

check your float height

 

You can play with float height and jetting but I had the same problem as you, I replaced everything from neddle and seat to jetting, I put the float a factory setting that is in the clymer manual, I tried it a little high, a little low but it still sucked. so I spent $150.00 on a Keihin PWK 35 air stryker and my quad has been a damn joy ever since, I cant recommend this solution any stronger. Good luck, by the way HITECH ATV appears to be the cheapest for Keihin carbs.