# Brute experts!! Need help ASAP!!



## etk2008 (Nov 18, 2010)

I have been messin with my bike FOREVER to figure this out. It has always ran fine until recently when the carbs will spit/backfire when it idles to about 1/8 of throttle. It will run PERFECTLY after about 8mph. I checked all the jets and they are spotless. Chokes arent stuck nor is the vent lines clogged up. Has new plugs in it too. Needles are shimmed too. Checked the valves, they are just right. I look way down into the carb bowl from above and see a spark whenever it spits. I dont know what else to do. Carbs are spotless but I did notice both carbs had 140 mainjets in it (located almost at sea level). Not sure if thats a problem for idling though. I usually can figure these things out but not this one!! Thank you for your help!!!


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## phreebsd (Dec 16, 2004)

i wonder if you would benefit from a carb sync?


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## etk2008 (Nov 18, 2010)

What in the world is that?? LOL


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## hondarecoveryman (Feb 28, 2009)

Between the 2 crbs ther is a carb. sync screw , yours is def. out of adj. look from the left side of the quad with left side panel removed you can see the screw between the carbs ,a long phillips head will get it , look down thru carbs to get the throttle butterflies even


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## MeanGreenMan (May 24, 2010)

Carbs being out of synch is not a common problem on carbed Brutes. Leave them alone if you didn't mess with it.

Test with partial choke and try to figure out whether you have a too lean or rich condition causing your current problem. For example, if quad idles and runs better with a slight choke on, it means your carb setting is too lean.


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## hondarecoveryman (Feb 28, 2009)

Not a common problem , but the symptoms he described led me to that not a A/F prob


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## gpinjason (Nov 10, 2009)

and you are sure the chokes are closing fully? my bike was the same way... didn't want to idle... and it was the chokes... make sure the cables aren't binding on anything also..

it could be the sync also though... or maybe just bad gas?


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## etk2008 (Nov 18, 2010)

Thank yall alot, Im sure the chokes are fine because it will idle perfect but it the rear will spit/backfire and every now and then the front will. But 99% is the rear. It idles fine and runs good, just that dang popping/spitting from the carbs get very annoying lol. Thank you for your help!


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## RDs Neighbor (Jun 24, 2009)

etk2008 said:


> Thank yall alot, Im sure the chokes are fine because it will idle perfect but it the rear will spit/backfire and every now and then the front will. But 99% is the rear. It idles fine and runs good, just that dang popping/spitting from the carbs get very annoying lol. Thank you for your help!


Try plugging your stock CDI in temporarily and see if that solves your problem. Most that have mentioned this issue have found that the advanced timing in the dynatek causes the problem. My solution was a larger pilot jet. Stock 750I is a #38. I installed a #40 and it stopped. I think the 650's are stocked with #40. You may need to go to a number #42. By the way, the sizes I mentioned are Kawie jets sizes. Not Dynojets.

Good luck.


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## 08bruteforce30s (Dec 5, 2010)

my 06 done the same thing. the sync was off and i didnt mess with mine.


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## etk2008 (Nov 18, 2010)

Yeah I was thinking maybe the sync, this is because the jets have not been touched for months and it just started this. Im just not sure exactly how to do this sync thing lol. Unfortunetly I do not have the stock CDI box. Yall's help means alot! Thanks!


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## tanowell (Jul 7, 2010)

I have a 06 that is doing a similar thing. It started when I turned in over going up a creek bank. Bike started right up after wards and ran great. However after sitting for a week it started to do the spitting/back firing problem, mostly the rear carb. If i took the airbox off it would shoot frames out. At start up i have to give it a little gas and run the choke for a while. At first start up and after warm up the bike spits/back fires. At low end and cruising it does it, but if i punch it it blows out and rolls. What's going on? A friend mentioned the valves need adjusting, whats the cold setting.


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## trailmaker (Jun 29, 2010)

I was curious if anyone found a solution for this problem... My 08 650i just started doing the exact samething could cold weather be a factor. MIne is also all stock exept air filter and a dynatek is on the way but wont put it in until I figure this out.

I want to check the sync between the carbs, and if anyone knows of a good site with a guide of some sort please reply... thanks


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## gpinjason (Nov 10, 2009)

trailmaker said:


> I was curious if anyone found a solution for this problem... My 08 650i just started doing the exact samething could cold weather be a factor. MIne is also all stock exept air filter and a dynatek is on the way but wont put it in until I figure this out.
> 
> I want to check the sync between the carbs, and if anyone knows of a good site with a guide of some sort please reply... thanks


it should be in the service manual... 

and cold weather could be a factor, but most likely something is dirty in one or both carbs causing it...


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## 650Brute (Dec 18, 2008)

Mine is a dog when its cold, sputters, backfires etc....

Has been put to the test deer hunting, alot of mornings were 10 F or colder out, fine once it warmed up well. But if I was in a hurry in the AM it sounded like a tommy gun sputtering down the hillsides.


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## denny (Jun 10, 2014)

*HELP! 750 Brute Force*

I have a 2005 750 brute force, popping through the carbs. The valves are fine, carbs are clean and there is no belt light on. Has anyone else had this problem, and what can I do to fix it?


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## blue beast (Feb 16, 2010)

Denny, what kinda mods you got on it, may be a jetting problem, or could have some problems with the rubbers that connect carbs to head



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