Backfiring Problems On A Honda Foreman 400

[NOT]

I have a 1996 Honda Foreman 400 4x4 that is backfiring pretty bad. It occurs when I drive it with the throttle wide open over a distance and then let off the throttle or when I'm coasting down a hill. I have had the float and the jet needle replaced on the carburetor, and I have adjusted the carburetor setting (for too rich or lean) as suggested in the owner's manual and it is still backfiring. Can anyone tell me what the problem could be and what I can do to stop the backfiring? Thanks.

[rpyfz450]

That sounds like a lean backfire because it happens when you're coasting. I know the Yamaha Warrior and YFZ450 have ACV circuits in their carburetors to reduce backfiring while coasting. Does your carburetor feature an ACV that's working properly?

[NOT]

I don't know if my Honda has or doesn't have an ACV circuit in the carburetor. Where would it be located?

[satrnfreak]

Hmmmm, i never heard of an ACV circut, but more than likely it is a fuel cut circut for coasting. Look on the side of your carb and see if there is a little plate with a couple screws holding it on. If you take those screws out, there should be a spring and a rubber diaphragm. Check the diaphragm for tears or holes. This would probably be your problem.....

frEAk

[85ATC350X]

Sometimes even the setting in the manual wont fix it. You are too lean on the on either the pilot jet or the fuel screw. start with the fuel screw turn it out further and further to see if it reduces the backfiring. Have you made any modifications to the air box or aftermarket air filter or exhaust?

[NOT]

I haven't done anything to the airbox and I haven't replaced the stock air filter with an after-market filter, but I have replaced the original muffler with another stock muffler I bought from the Honda dealership.

[Snafoow]

Check the exhaust for a leak. My bike gets a leak where the header pipe meets the muffler pipe and does just that when hot and decelerating :rider:
If not that Try the cab thing again

If the exhaust leak or fuel screw ideas dont fix it try to recheck the needle position because that can often times be behind a deceleration pop or backfire.