# 05 Brute isn't producing power



## jrbtzx12r (Feb 25, 2013)

Hello 

This is my first time posting so bare with me. I have an 05 Brute 750 (orignal owner) that's been sitting for 5 or 6 years since they shut down all of the good riding areas in Mass. It was only fired up occasional just to keep the gas from going bad in the carbs or to do the occasional plowing of the driveways when I lived in New England. Now that I'm in Utah I'm trying to get her running for the summer.

When I fired her up the first time out here she was running really rough. Backfiring and hesitating. She's been like that for years, but not as bad. So I pulled the carbs and cleaned them. They actually weren't that bad compared to my KFX400. Since cleaning the carbs she fires up on choke and runs for a little bit and stalls. She'll fire back up, but you have to be off choke and massaging the throttle till she's warm and then she'll idle just fine. Working the throttle there's no more backfiring, but she doesn't seem to produce that "snap" of the RPM climbing. It's more of a smooth build in RPM. When I try driving her I'm getting to 20mph max in high on 2wd.

There's no flashing lights on the gauges and everything appears to be running fine. There's only 62 hours on her and I can't for the life of me figure out what's going on.

What I've done so far other than cleaning the carbs (cleaned them separately so I didn't mix up the parts between the carbs) is put in new plugs, tried running her with the gas cap off, verified both plugs are getting spark, polished the slides in both carbs, and I tried shimming the needles in the carb. The plugs with the shims in were pretty black so I pulled the shims and cleaned the plugs. Also, I had two very small o-rings I found after cleaning the carbs. I have no idea where they came from. All of the small o-rings that were present before cleaning are where their supposed to be (specifically the air-cut valve). The only place I can think they would come from are the Pilot air assemblies, but when I pulled them there was no o-rings on either carb. I specifically looked for them because I saw them on the parts diagram. Any ideas where these go or if the Pilot really needs these o-rings?

I know there's about 4200ft difference in elevation between here and New England, but I wouldn't expect it to limit my max speed to 20mph. The stock jetting can't be that far off. 

Any help would be appreciated! Thanks.


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## dman66 (Feb 20, 2011)

Well those little o - rings could be from the air/fuel jet under each carb - if they're missing,she won't run right.The choke plungers could be hanging closed on either carb if they have not been cleaned and lubed,or the cables have tension on them that could close the chokes too.These quads take about 5 - 10 minutes to warm up on a 70 degree day.The air filter box seal to the lid needs to be good and the rubber boots connecting the engine to carbs and carbs to air box need to be leak free.Need to know more about spark plugs on each cylinder.If you open up air box after she warms up,take air filter and fire screen out,rev her up slowly and see if the slides are opening the same - sometimes we miss align the slisde diaphram gasket causing air leak or not installing the little brass air jet back in those diaphrams causing problems.If she went into limp mode the 2wd/4wd light would be flashing back and forth and you would experience very bad stuttering and popping from carbs - like going in reverse without the overide button pushed in.


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## brutemike (Mar 23, 2010)

Did you get rid of the old gas and put new in if not thats the main problem rite there.Even with new gas I would run some seafoam in the gas tank.Do this and find where those o rings go and you should be good.


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## jrbtzx12r (Feb 25, 2013)

dman66 said:


> Well those little o - rings could be from the air/fuel jet under each carb - if they're missing,she won't run right.The choke plungers could be hanging closed on either carb if they have not been cleaned and lubed,or the cables have tension on them that could close the chokes too.These quads take about 5 - 10 minutes to warm up on a 70 degree day.The air filter box seal to the lid needs to be good and the rubber boots connecting the engine to carbs and carbs to air box need to be leak free.Need to know more about spark plugs on each cylinder.If you open up air box after she warms up,take air filter and fire screen out,rev her up slowly and see if the slides are opening the same - sometimes we miss align the slisde diaphram gasket causing air leak or not installing the little brass air jet back in those diaphrams causing problems.If she went into limp mode the 2wd/4wd light would be flashing back and forth and you would experience very bad stuttering and popping from carbs - like going in reverse without the overide button pushed in.


I'll have to try to put the o-rings in the pilot jet to see if it makes a difference. I didn't see them there before, but they had to come from somewhere and that's the only location I can tell has them from the diagram. I'll also try to see if I can see the slides working after she's fired up. The choke cables seem to be working OK, of course I checked them when they weren't in the carbs. I think I may have run the front cable incorrectly though. The way it is now it's running under the mount for the carb on the throttle linkage enclosure. So the cable touches the cylinder. I think it's supposed to run over the mount. The rubber boots on the carbs are OK. I forgot to mention I checked them. I have let it warm up for several minutes before taking it out. When putting the diaphram on the slides back in I double checked to make sure they were seated correctly and the air jet was seated correctly (I thought the same earlier that they may not be lined up or seated correctly). The lid seal seems to be good on the A/F. Pulling it makes things really bad as I was able to experience that first hand and realize these things don't work right without that lid on. I'll double check it though. It's definately not in limp mode. The drive train seems to be working OK. 



brutemike said:


> Did you get rid of the old gas and put new in if not thats the main problem rite there.Even with new gas I would run some seafoam in the gas tank.Do this and find where those o rings go and you should be good.


I actually had to drain the tank and run her dry before the moving company would even consider putting the Brute on their truck. The gas is brand new and it has seafoam in it. After having to clean the carbs I'm running it in all my gas for the ATVs now. I'll check the o-rings this weekend.

Thanks for the help and I'll let you know how I make out.

Jr


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## dman66 (Feb 20, 2011)

O-rings go on the air/fuel idle adjustment screws on external bottom of each carb - You have the a/f screw needle,then install spring,then flat washer,then o-ring,then install into carb.


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## jrbtzx12r (Feb 25, 2013)

dman66 said:


> O-rings go on the air/fuel idle adjustment screws on external bottom of each carb - You have the a/f screw needle,then install spring,then flat washer,then o-ring,then install into carb.


Yeah neither the washer or o-ring was there when I pulled them. I'm wondering if the dealer pulled the carbs at one point and didn't put them back in. There was also a screw missing from one of the float bowls which makes me think that may be why their missing. 

Does anyone know the size of the flat washer? I'm thinking it may be a 4s like the ones for the needle fix.


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## dman66 (Feb 20, 2011)

I think thet the A/F needle washer is smaller.It's a hair bigger than the o-ring,but no bigger than the needle threads. Here is the part# from Rockymountainatvparts 16014-0009 listed as screw - pilot air.The diagram shows the air pilot screw,spring,washer,and o-ring for 12 bucks,under carb parts.Sorry you were right by calling it the pilot,but most of us call it the air/fuel screws.I have that set up if you need more info on it,I did go to a local well stocked hobby shop with rc cars,and they had washers the same size.


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## jrbtzx12r (Feb 25, 2013)

Quick update.

I checked the slides and they're working OK. Pulled the carbs again and fixed the choke cable that was touching the cylinder head. Put the o-rings in the A/F screw, but I couldn't find washers that would fit. There didn't seem to be any noticeable difference other than I was able to hit 25mph on a longer stretch.

So I've ordered a set of A/F screw assemblies which I hope make it here by the weekend. I'll update after I get them in and installed.


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## dman66 (Feb 20, 2011)

Other things to check is the fuel pump -is it pumping enough fuel to the carbs ? And did you check the fuel levels in each carb after the engine is warmed up during idling ? Is the air filter clean ?


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## rolaj4me (Dec 29, 2011)

Check for a pin hole in your carb diaphram had a 400 bombardier with no power hold throttle wide open rpms would slowly come up changed diaphram works like a champ now just a thought good luck


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## Wheelie deep (Mar 5, 2013)

*Help please*

Hey guys my 08 brute is acting up. I turn off the key and the kill switch but the actuator stays running and the display goes crazy. I half to disconnect my battery to make it stop


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## dman66 (Feb 20, 2011)

jrbtzx12r, 
Another thing to look at is the fuel level in the carb bowls - check the float height in the bowls.I was fooling with my float adjustments today,cause I have a fuel problem where fuel leaks out the overflows when wheelies or bumpy riding,and when you set floats to maintain a lower fuel level,the engine really loses power alot - set floats to 2.9mm,and all power you want is there.Still did'nt fix my fuel problem though.


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## jrbtzx12r (Feb 25, 2013)

Well I put the new A/F screw assemblies in. Set them to 2 1/4 turns. She starts and runs fine. It still doesn't seem like she's building power that quickly when tapping the throttle. Then again I haven't been riding for a few years and I'm wondering if its just me. There's no stumble or hesitation at all. Still only made 25mph in high gear. I did put her on the lift and she hit 60mph easy freewheeling. 

I did check the slide diaphragms and they look good. I have checked the fuel pump, but how would you do that? The pump looks to be vacuum powered and not electric.

I haven't checked the float bowl height, but I didn't replace the float or the needle so it should be the same from stock unless I bent them which I don't think I did. 

I'm beginning to wonder if this could be transmission related. Is it even possible for this belt to slip and possibly cause the lack of power?

Thanks


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## jrbtzx12r (Feb 25, 2013)

Quick update.

I thought I'd check the belt the other day so I fired up the Brute and held the front brakes while giving her some throttle. It caught once and started moving forward, but after that building the RPMs up didn't move her at all. So I pulled the cover and the deflection was over 28mm and the belt width under 28mm. So it looks like the plowing and dirt work I've done with her beat the belt down a bit. I ordered the tool and a new EPI belt. Hopefully they'll be here by the weekend, but I have a feeling the belt won't make it here until some time next week.


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## jrbtzx12r (Feb 25, 2013)

Well here's the update. Received the new belt and clutch tool ordered from Amazon (know where I'm going with this?). While using the clutch tool it snapped off inside the clutch. I was finally able to get a 3 jaw clamp and remove the clutch and broken tool without damaging anything. Put the new belt on and took her out today for a test spin. Max speed in 2wd in high was 27mph at a 1.4 mile. 

Any ideas? She seems to be running without any hiccups at all. Just won't give me the umph she's supposed to have. Thanks.


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## No_Substitue_For_A_Brute (May 4, 2011)

Did you set the belt deflection for the new belt? 

Sent from my ADR6400L using Tapatalk 2


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## redrumredrum89 (Apr 12, 2012)

I had the same problem .It was the computer .Swapped it out and ran hard as ever.


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## jrbtzx12r (Feb 25, 2013)

redrumredrum89 said:


> I had the same problem .It was the computer .Swapped it out and ran hard as ever.


What did you replace it with a Dynatek?


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## brutemike (Mar 23, 2010)

Dynatek is your best choice for price and quality.


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## dman66 (Feb 20, 2011)

Did you check carb float levels first before you spend some money ? If the floats are set too low in the bowls,you'll have the same problem.


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## jrbtzx12r (Feb 25, 2013)

dman66 said:


> Did you check carb float levels first before you spend some money ? If the floats are set too low in the bowls,you'll have the same problem.



No I haven't checked them. Just dreading tearing them off again.


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## No_Substitue_For_A_Brute (May 4, 2011)

Check your muffler and make sure it's not caked full of mud. I had mine clog up and caused running issues and speed issues just like you are describing. 

Sent from my ADR6400L using Tapatalk 2


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## Steve8511 (Dec 19, 2010)

Sure sounds like limp mode....


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## redrumredrum89 (Apr 12, 2012)

jrbtzx12r said:


> What did you replace it with a Dynatek?


Yes a used one at that.


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## jrbtzx12r (Feb 25, 2013)

I agree with the limp mode note. Has anyone ever heard of a Brute going into limp mode without the light flashing? All of the lights are working.

The Brute hasn't seen mud since about 2007. So there shouldn't be any worries about mud in the muffler.

I did receive the Dynatek this week. It's installed and she seems to run OK standing. Maybe a little more peppy on the throttle. I'll try to take her out Sunday morning to see if there's any change. If there's no improvement I'll pull the carb's again and check the floats. I don't deflection is off, but I'll check that as well.

The Dynatek removes limp mode right?


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## jrbtzx12r (Feb 25, 2013)

Well I was able to make 30mph and it seemed to get there quicker than before. So I think it's one of three things. Fuel starvation, somehow it's stuck in limp mode, or the CVT isn't operating properly. As far as the CVT goes if I put her on the lift and free wheel she'll hit 60mph easy. As far as belt slip I tried standing on the brakes and applying the throttle. She would lurch as soon as I tapped the throttle so the belt doesn't appear to be slipping at all compared to what I was seeing before the belt replacement.

This things killing me. Ugh....


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## dman66 (Feb 20, 2011)

I'd check the fuel pump output,and if that looks good,then check the carb floats - I do know if the floats are set too low in the bowl,you will lose power and speed - you can take clear tubing and attatch the tube to each drain valve at the bowls,and check the level against the markings on the carbs........


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## jrbtzx12r (Feb 25, 2013)

dman66 said:


> I'd check the fuel pump output,and if that looks good,then check the carb floats - I do know if the floats are set too low in the bowl,you will lose power and speed - you can take clear tubing and attatch the tube to each drain valve at the bowls,and check the level against the markings on the carbs........


Thanks! I'll try to take a look this weekend.


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