# 06 Brute Force loss of power and backfiring



## Jonhomemade

Hello everyone, I'm new here but have spent a lot of time reading up on this Brute the last few days.... Seems these things have a lot of problems....

Incoming long post, I want to try to provide as much detail as I can. I will add a tldr at the end.

A good friend of mine has dropped off a 2006 Brute Force 750 at my house that was having a lot of problems with over heating, fan not working, and battery not keeping a charge. I have a chance to buy this thing for pretty darn cheap, but will only buy if I can get it running good. After some reading I learned about the rear bus and cut it out and used solder and wire nuts to connect all the correct wires. Fixed those problems, besides the fan, which I just hard wired to a switch. But then when I would ride for maybe 20-30 min, I could feel, what I thought was the engine getting really hot, and the quad would start to backfire and have complete loss of power. (Mash the throttle and it will take off really slow and not want to climb hills and such)

After more research and pulling my hair out, I read about possible exhaust leaks, which it turns out it was leaking on the rear exhaust.(only had one nut.....) I then got the exhaust tight and stopped the leak. The quad seemed to get a lot more power and of course quit burning my leg from the leaking exhaust and I was happy... for about 20-30min until the quad warmed up and it lost it's power and starting to backfire again... I pulled the plugs and noticed they were fouled up and rather black.(cleaned them up and put them back in, they seem to be in good condition, were just dirty with black soot) I read about the choke maybe being stuck and/or running too rich. I pulled off the air filter, looked down in the carb and fired up the quad. The back carb was locked up (when hitting the throttle or using the choke the thing would stay closed. I pulled the plastic cap off the rear carb, cleaned the spring and made sure the rubber gasket thing was not cracked or broken. I put it back together and fired it up, and the back carb is now working in sink with the front carb when throttling. 

I again was happy thinking I have fixed the problem..... but again, my happiness only lasted for 20-30min (until it got nice and warm) and then I lost it's power and it started to backfire and sputter again. I stopped the quad and pulled the air filter off to make sure both carbs were still working and they both are.

I have read about maybe needing to adjust the pilot screws on the bottom of the carb and making sure they are both at 2-2.5 turns. I have also read about it maybe being a full pump / vacuum problem.... Before I go any further and stress myself out anymore I thought I would ask around to see if anyone knew what my problem is and what the fix is. Any help would be great! 

tldr: Quad runs great when first started. After 10-30min of riding the quad will lose power (Mash the throttle and it will take off really slow and not want to climb hills and such) and start to backfire and sputter. 

Side note: While I was cleaning the spring on the back carb, I noticed two "nipples" on the bottom of the carb with nothing attached to them. I also found a long hose that splits at the end into two small hoses just laying under the carb. (Long Y hose) I assume that goes on those nipples? I plugged them on and they fit snug, I then ran the end up the handle bars and poked out the front. I assume is was a vacuum or exhaust for the carbs? After doing so, I did not notice any change in how the quad was running, besides the same problems with loss of power and backfiring / sputtering after being driven for a bit.


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## Jonhomemade

I should add that if the quad sits for a couple hours it will run fine for about 10-30 min, and then lose power and backfire / sputter. Shut it off again and let it sit an hour or so and it will be fine for another 10-30min.......


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## JLOWERY

Check that buss connector 

KAWI RULES


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## filthyredneck

First off, thank you very much for taking the time to actually research...we constantly ask our members to do that before asking a question thats already been answered a million times and theres still always the ones that just can't get the hang of it lol. Also, welcome to the forum 
Ok, on to your problems.....the Y hose that you found should be the drain hose to the carb bowls, they have little allen screws that will open the drains up...no need for that to be ran up high honestly. And the actual problem with running poor when it gets warmed up, fouled plugs, high heat on your leg.....sounds to me like your choke plungers are froze up in the carb. You'll have to dig a little deeper to get to those, and will probably have to remove the carbs.

"Killing Time Using Tapatalk 2"


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## Jonhomemade

filthyredneck said:


> First off, thank you very much for taking the time to actually research...we constantly ask our members to do that before asking a question thats already been answered a million times and theres still always the ones that just can't get the hang of it lol. Also, welcome to the forum
> Ok, on to your problems.....the Y hose that you found should be the drain hose to the carb bowls, they have little allen screws that will open the drains up...no need for that to be ran up high honestly. And the actual problem with running poor when it gets warmed up, fouled plugs, high heat on your leg.....sounds to me like your choke plungers are froze up in the carb. You'll have to dig a little deeper to get to those, and will probably have to remove the carbs.
> 
> "Killing Time Using Tapatalk 2"


Well I thought it was the rear choke plunger froze up again on the rear carb causing the problem since it was doing it before I cleaned the spring, but when it warmed up and first started to lose power and backfire I pulled off the air filter and looked down in the carb and both plungers are working in sync. I read something about the chokes on these screwing up a lot and causing this problem and someone said to "delete the choke".... Sorry, I don't know what that really means. Does that mean to remove the choke? If so, can someone point me in the right direction to do this. I truly think it is a problem with the choke getting stuck and if I can just remove it as a quick fix for now to make sure it fixes the problem it would make me happy till I get the choke issue fixed.

Sorry, I'm really not the best mechanic, but I'm trying to research and figure all this out without paying someone. I want to fix it myself and learn more as I go.

And, thank you guys so much for taking the time to read my problems and trying to help!!

Edit: Also the heat on my leg was fixed when I fixed the leaking exhaust.


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## Jonhomemade

JLOWERY said:


> Check that buss connector
> 
> KAWI RULES


The buss could cause this problem with loss of power and backfiring even know the connector has been removed and the wires soldered? Thinking maybe I don't have them all connected good enough?


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## dman66

I would say you need to pull the carbs off,pull off each choke plunger on the sides of carbs - clean the brass plungers - dielectric grease the plungers - reinstall plungers.Open up fuel bowls and check the pilot and main jets - take note to what brand and size each jet is - stock 750's would be Keihin jets - #38 pilots, #152 main front, #158 rear,the needles in the carb slides would be a NFKK front and a NFKL rear or Both NFKL is ideal,2 1/2 turns out on air/fuel screws.You may want to install one #4 brass or steel washer under each needle helps the carb transition from idle to say 1/2 throttle.Also have you checked the valves to insure properly adjusted.Have you checked the carb vent lines and gas tank vent lines,check for cracks in the vaccum lines from carbs to fuel pump.There's more,but these are the starting points.Be patient .....


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## chevzr2

you can't see the chokes working when you look into the carbs, what you see through the airbox is the slides working, you have to pull the carbs to work on the chokes!


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## wjpelka

*Could it be starved for fuel?*

Any chance that after 30 mins of riding you could be pulling a vacuum in the fuel tank? This would be starving the carbs for fuel. Then, while you are trying to find the problem, enough air "leaks" into the tank, removing the vacuum and it runs fine again, for about 30 mins. Might try running with the cap loose for a while. Who knows...


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## Jonhomemade

Thanks a lot for all the help and info guys. After more reading and looking over the quad I think it is going to be a vacuum problem. I'm about to head out and strip everything off and check all the lines. I did find one of the vacuum lines coming off the carbs that ran up the handle bars that was nearly burnt in half. Going to replace that and check the line from the fuel pump to the carbs. While I have everything off I'm going to check everything dman66 said on the carbs. Thanks again, and I will report back when I get it stripped.

I do have one question, these diagrams kind of confuse me. I'm not sure about the vacuum line from the fuel pump to the carb... Is what I have in the pic the vacuum line, and does "A" run to "B"???


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## movingman

"A" is where the fuel comes into the carb from the fuel pump. Where you have the arrow I believe that is your fuel line. A and B are connected by that hose


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## dman66

"A" is fuel line to carbs."B" picture shows the fuel pump - the two hoses in the circle are - upper hose vaccum,lower hose is fuel to carbs, I believe. The vaccum lines go to just below the carb boots to each head.The carb vent line should be run to the pod without any blockages in the line - the white cannister in that line can be used,just seal up the 3/8" hole in the side of it with a little caulk.


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## drtj

Alot of great info in this thread!! I have a quick question. What is the best way to see if you have an exhaust leak? I think i have a small one at the rear head. Ive thought about submerging it in water. Any other ways to check?


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## brute for mud

Yes with it running take your hand and feel around the pipe for hot air blowing be careful you can get burned by the pipe


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## Jonhomemade

drtj said:


> Alot of great info in this thread!! I have a quick question. What is the best way to see if you have an exhaust leak? I think i have a small one at the rear head. Ive thought about submerging it in water. Any other ways to check?


My exhaust leak was bad enough I was able to feel the hot exhaust blowing out where the pipe connects.


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## DaveMK1

drtj said:


> Alot of great info in this thread!! I have a quick question. What is the best way to see if you have an exhaust leak? I think i have a small one at the rear head. Ive thought about submerging it in water. Any other ways to check?


Put a dollar bill near it and see if it moves. Little safer than using your bare hand


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## drtj

Thanks for the help on ways to check. Havent got around to doing it yet. Did find out why it was running like crap though. Had a clogged vent line.


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## fixitguy63

mine is doing something like this but it runs rich at idle but runs good at half and full throttle. the rear plug was pretty black so I changed them and checked the spark and the spark is good on the front and back but it still runs that way. mine is a 08 teryx though. any body found anything that fixed thiers?


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## Wheels82

filthyredneck said:


> First off, thank you very much for taking the time to actually research...we constantly ask our members to do that before asking a question thats already been answered a million times and theres still always the ones that just can't get the hang of it lol. Also, welcome to the forum
> Ok, on to your problems.....the Y hose that you found should be the drain hose to the carb bowls, they have little allen screws that will open the drains up...no need for that to be ran up high honestly. And the actual problem with running poor when it gets warmed up, fouled plugs, high heat on your leg.....sounds to me like your choke plungers are froze up in the carb. You'll have to dig a little deeper to get to those, and will probably have to remove the carbs.
> 
> "Killing Time Using Tapatalk 2"


Stupid question but can you take the plungers out completely? Or would the brute not run right if you took em out?


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## NMKawierider

Wheels82 said:


> Stupid question but can you take the plungers out completely? Or would the brute not run right if you took em out?


Nope. Can not. The plungers seal-off the port to the bowl and the intake track and the springs push the plungers against the port when closed.


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