My buddy's '01 Honda foreman 450 backfires badly on deceleration!!! It has about 3,000 miles on it, and I'm
not sure if it has ever had a tune up. I told him to go buy a new spark plug, fuel filter, and air filter. But was wondering if anyone had any other Ideas??? Could the park arrestor be getting plugged??? Any help
would be appreciated!!! Thanks, Dan

 

Doesn't anyone have any ideas????

 

its somewhat normal for a small pop or two, but i would first jsut wash the airfilter. a dirty filter wont flow as good and can change how it runs. start from there, jsut wash it up good and remember to re-oil it. our foreman is an 03 with 4000 miles, but with the proper matinance it still runs like new.

 

theres an easy fix for this... go 1/4 to 1/2 turn out, (richer) on the mixture screw. If this doesnt get rid of it, then look for exhaust leaks, and/or intake leaks. Something is leaning the idle mixture.

 

I've had the same problem you describe, except that it was just one pop and it was happening rarely, but in decelleration . .

I've tried to richen the mixture with no change ..

I've put an K&N Air Filter and rejet the carb since then ... It seems to be less frequent . .
And I don't think your spark arrestor could do that ... Well, it's my opinion!!
By the way, I splitted open my own muffler and remove some parts in it, the spark arrestor and some tubing... And the backfire is
still present, even if I don't have leak in the muffler or pipe.. My carb seems to be adjusted correctly, and every time I have backfire I richen the mixture 1/2 ... and it did not change anything ..

So the problem may be normal, if the backfires are not frequent . . .

It happens to me like 1 time in a 2 hours ride ...

 

Loster, how many turns out ,is the mixture screw? If youre beyond 4 turns out( from seated), then the pilot jet is too small. Go one up on the jet, and readjust the mixture screw.
Theres a good chance your right, that you'll have to live with it, seeing how you've modified the exhaust,.... but on a totally stock foreman, it shouldnt ever pop or backfire.

 

Well, Before I rebuild the muffler, I was out maybe 4-5 turns ..
Now, I must be about 4 out ..

By the way, I rebuild the muffler for one reason, there was a loose piece in it, a tube that goes from the rear of the muffler
to the middle, and it has a restriction plate and the middle of the muffler, I removed this also . .
For the spark arrestor, I tried to fix it, but it is too thin metal and in a hard to reach place, so I simply removed it and replace
it with a 1/8 steel plate about 1 inch wide ... The spark arrestor was kind off "leaking", the exhaust was passing between
it's connection to the muffler core in some places, so it made an awful sound . ..
.. it does not make the job of the spark arrestor, but when I have the cash, I'll buy another muffler ...

Now, I have a pretty evil sound less restriction, and not so loud, so I find it very cool !! .. And don't have as many backfires as before ...



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By the way, I installed a DynoJet Jet kit in the carb .. . So I'm richer than before, that may explain the less frequent backfires . . ...