backfiring??

[EPDP99]

I am getting a backfire type pressure that comes back through the carb. it doesnt backfire but more like way too much backpressure. motor is 465 stroker, 12.5:1 je piston, web 450/451 cam, port and polish, 3 angle valve job, shortened retainers, big gun rev box, fcr 41mm carb, trinity pipe. head pipe is almost stock size then steps up. could the head pipe be putting to much back pressure on the motor causing this. also power is down. today found out timing was off and had to move one tooth on the cam gear. i might look into moving it once more because it is very slightly off. could the timing also be causing this.

[AdvantageCycle]

not sure what your piston/valve clearance is, but if you know the cam jumped time, sounds to me like a bent or damaged valve. I would check this out soon, because intake backfires are known to cause fires!

[EPDP99]

it also has the chamber mod which i think has to do with the clearances. one tooth barely moved marks on the cam gear. engine has never made a ping or any noise that would even think piston hit valve. it would be really messed up if it was.

[SnowFlake]

Mine does the same thing with the carb when i shut off the choke if its not warmed up all the way. Every thing is stock on the quad.
but once it warm up its fine. HELP US!!!

[EPDP99]

mine has no choke and the slide slaps front to back. not constantly but random. Thats why i think it is a timing thing. it also does it when you start to throttle up. need advice!!

[mojoe2878]

it does sound like your timing is still a little off, it sounds like it is firing before the intake valves are closing all the way, try to advace the timing a little if you can or you may need to get an advance key before its over with.
either that or you have a burnt valve seat that isnt sealing good.

[cals400ex]

i would first make 100% sure both of your air boots are sealed tightly around the carb and also make sure neither has a crack in it. sometimes you need to look really close for the cracks. what does it pop? when starting it? what letting off the gas? also, try the stock ignition box and see if it still does it with that one. on startups my aftermarket ignition box makes it pop through the carb.

[EPDP99]

no it does it sparatically while idling and when you start to give the bike throttle. bike is going back to trinity because it came to me with the timing off. they are taking care of me on getting it fixed.