backfires

[abraptor]

i was wondering if anyone knows why my quad backfires. it runs good when it is warm but down shifting or when i get out of it it will backfire. it does have an aftermarket pipe. does it need new jets? does this mean it is getting too much fue or not enough? i appriciate the help thnx

[Midwest Trail Rider]

Sounds like you need new jets to me. Give us a little more info. What model is it? What pipe are you running? Does it have a air filter?

[abraptor]

its an 05 raptor 660 with a pro circut t4 pipe and it has a stock airfilter. thnx for responding so fast

[Midwest Trail Rider]

Contact Pro Circut they might have the proper jetting all planned out. Moto Mavrick might know more about propper jetting than I do. Maybe send him a PM if he doesn't find this thread soon.

[Adam]

Normally, the backfiring comes from timing or valves. But it can also be attributed to the fuel air mixture - often too lean.

1. An engine in a flooded condition and trying to start will backfire because unburned fuel has passed the exhaust valve and ignites in the exhaust system.

2. When running with a lean mixture you can get pre-ignition with the excess oxygen relative to the fuel in the mixture = backfire.

3. An engine throughput is a flow of air, mixed with fuel in the mid path, converted to exhaust in the combustion chamber. That flow of air is thrown out of balance with exhaust or intakes not designed to accommodate that flow design = backfiring and other performance issues.

In your case, I would say it's coming from the exhaust system, but you may very well be able to compensate by going to richer jets or adjusting the upper rpm (load) settings on the carburettor.

[Midwest Trail Rider]

Originally Posted by Adam

Normally, the backfiring comes from timing or valves. But it can also be attributed to the fuel air mixture - often too lean.

1. An engine in a flooded condition and trying to start will backfire because unburned fuel has passed the exhaust valve and ignites in the exhaust system.

2. When running with a lean mixture you can get pre-ignition with the excess oxygen relative to the fuel in the mixture = backfire.

3. An engine throughput is a flow of air, mixed with fuel in the mid path, converted to exhaust in the combustion chamber. That flow of air is thrown out of balance with exhaust or intakes not designed to accommodate that flow design = backfiring and other performance issues.

In your case, I would say it's coming from the exhaust system, but you may very well be able to compensate by going to richer jets or adjusting the upper rpm (load) settings on the carburettor.

I agree totally but on quads this ushually happens when you put a aftermarket pipe on. Jetting fixes it.

[MOTOCROSS MAVERICK]

I would have to say it is your jetting that is off. What else doe it do? Like doe it bog when you stab that throttle? Also look in the exhaust and what color is it. White or black?

[abraptor]

thanks for the help i put new jets in and it does not backfire anymore

[MOTOCROSS MAVERICK]

good deal! Glad you got it going!