hey guys ive been doin a lot of searching for raptor backfiring problems, but my problem seems to be unique. The quad had been standing up (on the wheelie bar) for 2 weeks. prior to being stood up the quad ran excellent for about 2 years before, it has a fmf power bomb header and exhaust and jetted. Now when it is started it fires right up in 15 degree weather idles excellent but as soon as you touch the gas it backfires and wont run. Rebuilt the carburator no difference whatsoever (not much of any particles in the carburator) im stumped i feel like it might be a timing issue or coil issue.

any help is appreciated, thanks Dane

 

one other thing i forgot to mention is that when i take the plug out it is soaking wet with gas after the backfiring.

thanks dane

 

what size jet are you running???? it sounds like you either have a partially clogged jet or are over jetting for the cold weather. One other possibility is your floats have shifted and now your floats are running too high. Did you drain the fuel out of the carb when you stored it. I hope this helps

Aaron

 

Is your parking brake on?

 

i ran into the same problem on a250r make sure your pilot jet is tight and is not loose or ran almost all the way out

 

i had the same exact problem with my stock raptor..took it to the dealer and they asid it was fixed but few days later same thing..i just replaced the jets and piped it with air filter and it fixed the problem. i think it was a clogged jet.

 

I had the same problem with the backfiring so I changed the spark plug and adjusted the valves and has been running perfect ever since your problem maybe a little more complex but it did a world difference for my Raptor

 

Mine did that once and I had connected a wiring harness underneath my hood that I thought should be connected well it wasnt I guess it was basically the same principal as having your parking brake on... check the parking brake

 

Hello 240sx i know this is a old subject but you said your raptor 660 was not running good. My raptor is doing the same exact thing.I was wondering what you had found out about yours?Thanks.