here is my problem. when i run my bike hard and let off the gas it will sometimes backfire on me. Had my friend look at it and we pulled the plugs and found that they were black from what appeared to be a rich fuel problem. we dropped the jet sizes down from 158r and 152f to 152r and 145 front. we rode it a while and it took care of the carbon on the plugs but still have a backfire, and I lost about 4 mph on top end. does anyone have any suggestions? I have 1550 miles on it now and never had the valves set. is that something I should check and if so what is the clearence they need to be set at. I am also looking at putting a highlifter cdi box on it next week. the loss of speed is not that important to me but now my wifes bf 650 will beat mine in a race., but the backfireing is imbarrassing when i ride with all those GRIZZLES cause they never let me here the end of it. I need all the help i can get. thanks

 

your manual should tell you what to set your valves at.
and i'll bet that is probly what your trouble is if there loose thay will open and close at the wrong time and cause it to backfire.
it dont take much to make that happen.
my honda was doing the same thing and after we ajusted the valves the backfireing was gone.

 

I WILL HAVE TO SEE IF THEY HAVE THE SPECS IN THE BOOK OR I WILL CALL THE DEALER.

 

Valve clearance specs should be in the owners manual. I would bet that your backfiring is cause by the rich condition that you indicated.

 

Check all of your carb boots,exhaust flanges make sure they are tight backfiring on decell is a lean condition my 650 did the same thing .Also have you had the needle change in the front carb valves do need checked also.

 

Backfire through carbs=lean. Backfire through exhaust=rich.
Backfiring is the combustion of unburned fuel in the exhaust UNLESS there is a timing issue or a valve open isssue.

 

well I checked the valve clearance "which I found in the owners manual" and I checked all the carb boot clamps, exhaust flanges , and I still get the backfire. someone said it might be a timing issue? how would I check that or would putting the new module on help with that? this is starting to get me frustrated. I don't want to take it to a dealer because i got skrewed last time i did that. They did not put it back together right and a lot of bolts were missing! need help can not take the hipe from the grizzly owners on this backfire!!!!!!!!!!!

 

haha, i bet if u had a grizzly instead of a brute and that happened to u then ur friends with grizzly's would try to help u as much as they could but since u have a brute they just stand tere and laugh at u. lol, i have no clue wat u should do but good luck! i dont like taking quads or bikes back to the dealer because they just rush and do w.e they want as long as it gets done. they dont really care bout it, they just "repair" it and send it out the door.

 

I bet you are still rich.

 

who me? haha, man, im far from rich. i have no money, im 14.