Either your choke is sticking and or you need to do a plug chop & check plugs and adjust main jets as necessary or Have the dealer pay someone to do it for you.

Assuming you have not overserviced your engine oil , over-oiled your air filter and filter is clean, you don't have any exhaust system air leaks, all your vaccum lines are connected correctly in and under your airbox, and carbureators & manififold boots are tight & not missing Sync caps & your snorkel is not plugged with foreign matter & , No Water is in your Air box snorkel drain.

Usually if plugs are black after a highspeed throttle chop, you are rich, if its caughing/popping in the airbox from idle to 1/4 throttle you need needles adjusted/shimmed.

Also Might switch your CDI with another Brute to see if OEM CDI is the problem.[img]i/expressions/face-icon-small-happy.gif[/img][img]i/expressions/face-icon-small-happy.gif[/img]

TuffEnuff

 

hey bud, could you send me a copy of that tsb on the brute force...about the back firing problem? my email is entrer1@comcast.net Also what web site did you get that from?

 

I went through the whole replace the front needle thing. Unfortunately I had to pay for the part myself in addition to the long 90 degree screwdriver tool which allows you to adjust the idle screws while it is running (very helpful and worth the $20). It ran better but I still had missing issues and it didn't really run as good as I thought it should.
MY SOLUTION: Buy the Dynojet needle and jet kit (also sold as K&N)!! It is a bit of a hassle as you'll have to remove the carbs, airbox and side panel to install the kit but it will fix your problem!!! If you can operate a screwdriver and some wrenches, most folks should be able to do it themselves. Probably took me about two hours or so to install it.
They are down to around $52 on Ebay and $60 a few other places. I got mine for $52 including shipping to my door on Ebay.
I know! It really sucks to have to put aftermarket parts on a new uqad to get it to run right, but that's what I had to do. Now mine runs great through out the entire range with NO missing or studdering. I don't think the horsepower gains noted on the packaging are realistic, but just the fact that it runs nice and smooth through the entire range makes me happy enough.
One note, you do need to have a pretty good idea at what elevation you'll be riding. This is true with the stock jetting too. If you live at 6000', your stock jetted quad is probably pretty rich at that altitude. If you live at sea level, you may be a little lean, but Kawi probably jets them on the rich side for that reason. The kit comes with all the jets you would likely need to set it up for any elevation, but you do have to know where you're at. .
The Dynojet kit gives you all the jets you need for almost any elevation (Dynojet numbers do not jive with Kawi jet numbers however).
Other than this issue, I love my Brute!!!

 

I just bought a new BF I haven't been able to really ride much just around the dealer ship and on my street. It really isn't as impressive as I had hoped for. I also have a 2005 Grizzly that I have made some mods to and it seems to be much quicker than the BF?. I realize that it will run better once I have broken it in " I HOPE", but I have heard there is a new CDI module that’s called DBF, or DB5 something like that?. Also I would like to pipe it, K&N, Dyno, ECT. Any thoughts would be great. My friend has a Polaris 800 EFI that I have to be able to beat.... I can't quite get him on the Grizzly even with all the mods that's why I bought the BF, but I am sure he will kick my but if I don't make some performance mods.

Microtroy@***.net

THANKS

 

Microtroy,

My BF is completely stock (so far!), and has about 17 hours on it now after breaking it in per the manual. I can easily catch up with and overtake my buddy on his '05 Grizzly, which is also stock with the exception of a front winch and some 26" Bear Claws (heavy, I know). I'm probably going to look into the Dynojet kit that mikeames described above, as it still has a backfire after the needle update. Other than that though, I love it and will be installing my winch and some decent tires as soon as I can make up my mind about which ones to get.

 

farginicehole,

Thanks, yes’ my Grizzly has White Bro exhaust, K&N filter W/outerwear, Dyno kit air box mods, 26” ITP mudlites on ITP “C” wheels runs extremely well. I just can’t quite beat that Polaris 800 EFI. I went out today and bought a full Big Gun system, Dyno jet kit and an air box mod that I suspect will wake that BF right up….. Thanks again

Microtroy

2005 Grizzly
2005 Brute Force

 

Cool! I'm new to ATVs, so I assume a Big Gun system is a performance exhaust? Please let us know how those mods affect your Brute's performance. Sorry lastcall 102, I feel like I kinda hijacked your thread. Hopefully someone can answer your question about the occasional bad exhaust backfire, assuming you haven't found a solution yet. Mine does that too still once in a while, usually during hard deceleration, so I'm also interested in possible solutions.

 

Farginicehole,

Yes, the Big Gun is exhaust and I will definitely pass on the information to the group. I will also take some pictures and record all of the part #’s associated with the upgrades.
I have been working on cars and bike for 25 years so I feel confident the upgrades will go smooth. This way I can Email it out to those people who would like to duplicate the mods. I won't be satisfied untill this Brute jumps off the ground when I hit the throttle.

Microtroy

 

microtroy, your Brute won't beat a Polaris 800? I had high hopes that I could squash one of those. do you loose the long haul or the short haul or both?

 

I'm kinda surprised a modded Grizz won't beat it. Is that Polaris highly modified or something? How fast will your Brute and Grizzly go top end? My stock Brute will hit 67-68 by speedometer, but I haven't taken my handheld GPS along yet to see how that compares. Sounds like many others' Brutes are a little faster than mine (I'm talking just the stock ones, of course!) too. Aren't the Polaris' quite a bit heavier than the Kaw or Yami?