bike keeps backfiring and dies

[jay]

when i get 3/4 throttle and beyond the bike dies out and while it is slowing down it backfires terribly. i just rebuilt the carb and don't believe that it is the problem. the top end has a tapping/rapping noise. adjusting the valves has not helped. does this point in the direction of having the top end rebuilt or is there something easier to do?
it is an 85 250sx

[NOS_350X]

my gess would be that you just need to adjust your timing chain

[timex69]

hey man try this
make sure the intake isnt cracked, make sure your floats are attachced properly and u have the gaskets in good shape that connect the airbox to the carb and the carb to the cylinder.

Good luck
al

[bbechtel16]

Maybe you need a different main jet?

[J.D.]

Uhhh....sounds like your choke is stuck open.

[Levithan]

Sounds like a timing problem. Im not sure how to adjust it, but does it sputter at all when you accelerate? Also, the tinking noise sounds similar to a problem that my friend had. He started hearing it when we were on a ride, and it sounded like something was tapping on the case from the inside. He let it go, and at the top of a hillclimb the bike just died. When we got it back to the shop, we found that his cam had sheared in two! Makes me think that you should open up the top end and have a look to make sure everything is ok. Well, thats my 2 cents!