Backfiring

[Ryan]

Aside from the new filter airbox is stock too

[alantf]

Have you checked the valves? Seem to remember that on older vehicles (many moons ago) that valve timing could affect this. Just a guess, at best. :??:

[Ryan]

Have not checked the valves it only has 1700 miles. I dont think that would be the problem.

[alantf]

Maybe not, but Suzuki recommend a check at the 1000km (620mile) service. Just sayin'. :2tup:

[jonathan180iq]

Originally Posted by Ryan

I have not checked the plug. I have replaced the gaskets on the header. it is also tight. I have not drilled any holes in the exhaust. the exhaust is stock. I am now however running a k&n air filter and a 130 main jet instead of 120 to compensate for the better air flow. Still sputtering on decel though. I dont think it is in the carb anywhere

So then you've adjusted the main jet. How about idle jet and needle? That's where the decel would be affected.
Main jet is mostly only for WOT.

[sarahrose1420]

Hello my name is Sarah.
I have a 2004 gz250 that backfires as well. I have checked everthing Ryn has mentioned and still it backfires. The only thing it has that is different is, the last owner did drill holes in the end of the exhaust.? Any help would be appreciated.
Hugs and Kisses,
Sarah Rose.

[geezer]

ohh hugs and kisses? yaya! how bad is the backfire? my bike does have a little put put noise when i get off the throttle but its nothing to concern with. you have a drilled muffler so im sure its gonna mke some noise, but that also means your bike might want more fuel to compensate form the increase capacity for airflow. try putting a 20 pilot in there and adjusting your idle mixure like blain says, warning i did this today and it was a major pain in the ass, hot engine burning my hands ouch.

[Water Warrior 2]

Or you could just plug the extra holes in the exhaust and see if it is to your liking.

[sarahrose1420]

I will try pluging the holes. But where is the mixture screw located,? I can't find it. All the holes on the side of the carb on my bike seem to be pluged off, is it under the float bowl somewhere.?
Thanks,
Hugs and KIsses,
Sarah Rose.

[DAN]

Check the decelaration circut in the carb. It involves the smaller side diaphram and the associated jets. after 10 years or so the diaphram gets stiff and cracked (new ones at bike bandit dot com). The jet behind the small diaphram could be blocked and the passage under the spring loaded check ball could get a shot of carb cleaner and a shot of wd40 (stick the pray straw into the hole and depress the ball under the small diaphram plunger). This circut enriches the fuel mixture on decelleration with the throttle closed. --Dan--