[Leadslinger_90]

Hello everyone, this will be my first post on this forum.
I recently acquired my first Brute. A used 06 750 Brute that isn’t running/starting optimally.

Bike is Very hard to start when cold and have to pump the gas repeatedly, once running I have popping through the carbs. I’ve done some studying and went ahead and proceeded with the following-
New plugs
New fuel pump
Fuel filter
Oil change
Coolant flush
Valve adjustment … (I’ve watched/read everything on TDC and double checked myself)
During the valve adjustment I had some issues with the front cylinder intake valves. Seems the rockers will close all the way against the valve stem even when the adjusters are fully removed. I can take a screwdriver and pry the rocker up and get a loud “click sound” and the rockers will return in the upward position like needed. (Almost like it’s under spring tension) Anyways, after adjustment the quad starts better but I still have a ping and pop at idle to 1/4 throttle. Runs good when opened up. So I proceeded to pull the carbs and inspect/clean. After some research I believe this bike has a 650 carb installed.(judging by pictures) . Could this be my problem? Will a 750 work with 650 carbs? Bike only has 2300 miles and 300 hours. But seems to have had a rough life. Other than that I know no history , could somebody have put a 650 motor on this 750 frame? Or just put a 650 carb on it? with the work I’ve done so far the only other thing I can think to check besides carbs are the cdi box.
(has dynatek installed currently) thanks so much for-any

input!

 

[Leadslinger_90]

Also meant to add- when the air box is off you can see that the back carburetor is the one popping and spitting.

 

[NMKAWIERIDER]

That is a set of 650 SRA carbs...and I do not believe they can be put on a 750 because of hoe the heads are. Al;so, they will not fit the 750 airbox and it must have one on it to run correctly. Without it, it will just spit and sputter above 1/4 throttle. Post some pics of the full machine, front, back and sides. And no, you can not put a 650 SRA engine in an IRS frame so...lets see the machine.

Also, on the valve issue, if the rocker is seized on the shaft, most often it's from a lubrication problem. Otherwise, one of the old Kawasaki problems was valve seats wearing so fast the stem comes up and touches the rocker even with the adjuster out so..in either case it may well need a top end job at least. Also, no 750 had a filter other then the one in the tank as they had pulse-type pumps that ran on vacuum and it wasn't strong enough to pump fuel through an inline filter. The 650 SRAs had an electric pump I do believe.

 

[Leadslinger_90]

That is a set of 650 SRA carbs...and I do not believe they can be put on a 750 because of hoe the heads are. Al;so, they will not fit the 750 airbox and it must have one on it to run correctly. Without it, it will just spit and sputter above 1/4 throttle. Post some pics of the full machine, front, back and sides. And no, you can not put a 650 SRA engine in an IRS frame so...lets see the machine.

Also, on the valve issue, if the rocker is seized on the shaft, most often it's from a lubrication problem. Otherwise, one of the old Kawasaki problems was valve seats wearing so fast the stem comes up and touches the rocker even with the adjuster out so..in either case it may well need a top end job at least. Also, no 750 had a filter other then the one in the tank as they had pulse-type pumps that ran on vacuum and it wasn't strong enough to pump fuel through an inline filter. The 650 SRAs had an electric pump I do believe.

thanks for the reply, I will go try to snap some pics of the rig. The fuel pump on this one is a mechanical one and the fuel filter it had is an inline. Maybe need to go ahead and delete it? I was looking at replacing the carb and upon searching “brute force 750 carb” every one I found looks different than the one I have.

 

[NMKAWIERIDER]

thanks for the reply, I will go try to snap some pics of the rig. The fuel pump on this one is a mechanical one and the fuel filter it had is an inline. Maybe need to go ahead and delete it? I was looking at replacing the carb and upon searching “brute force 750 carb” every one I found looks different than the one I have.

Lets see the machine first.

 

[Leadslinger_90]

That is a set of 650 SRA carbs...and I do not believe they can be put on a 750 because of hoe the heads are. Al;so, they will not fit the 750 airbox and it must have one on it to run correctly. Without it, it will just spit and sputter above 1/4 throttle. Post some pics of the full machine, front, back and sides. And no, you can not put a 650 SRA engine in an IRS frame so...lets see the machine.

Also, on the valve issue, if the rocker is seized on the shaft, most often it's from a lubrication problem. Otherwise, one of the old Kawasaki problems was valve seats wearing so fast the stem comes up and touches the rocker even with the adjuster out so..in either case it may well need a top end job at least. Also, no 750 had a filter other then the one in the tank as they had pulse-type pumps that ran on vacuum and it wasn't strong enough to pump fuel through an inline filter. The 650 SRAs had an electric pump I do believe.

 

[Leadslinger_90]

 

[Leadslinger_90]

 

[Leadslinger_90]

 

[Leadslinger_90]

 

[NMKAWIERIDER]

Well that is not the 750 air box and it looks like the side plastics are from an SRA. May have adapted a 650 into a 750 frame. Back up and take a photo of the rear and look on the front cylinder for a 749cc or a 649cc casting. In ant case, those are 650sra carbs and airbox. May have a Frankenstein there. But sith some adapting you can pit anSRA engine in a IRS frame...it's just not easy.

 

[Leadslinger_90]

Well that is not the 750 air box and it looks like the side plastics are from an SRA. May have adapted a 650 into a 750 frame. Back up and take a photo of the rear and look on the front cylinder for a 749cc or a 649cc casting. In ant case, those are 650sra carbs and airbox. May have a Frankenstein there. But sith some adapting you can pit anSRA engine in a IRS frame...it's just not easy.

Well that is not the 750 air box and it looks like the side plastics are from an SRA. May have adapted a 650 into a 750 frame. Back up and take a photo of the rear and look on the front cylinder for a 749cc or a 649cc casting. In ant case, those are 650sra carbs and airbox. May have a Frankenstein there. But sith some adapting you can pit anSRA engine in a IRS frame...it's just not easy.

Here is the rear end of the machine, thank you for all the help. When I got the quad, the body plastic that goes on top of the air box was missing, maybe because it wouldn’t fit on with the 650 airbox. I’ve looked on the cylinders and all over the motor the best I could. The only numbers I found that I could half way make out seem to be 0633?

 

[NMKAWIERIDER]

Looks like someone had either put a 650 SRA top end complete with carbs and airbox on a 750 bottom end...which I am not sure can be done.. or has modified the output tail shafts of an SRA to work in an IRS machine. If they had used a IRS 650 engine it would have dropped straight in as they are identical to the 750 except for the CCs...and as I look up things, the 650 cylinders were cast with a code that did have 633 in it where the 750s had 749. Good luck on this one. The engine serial number can be decoded to tell you what it came out of.

 

[Leadslinger_90]

Looks like someone had either put a 650 SRA top end complete with carbs and airbox on a 750 bottom end...which I am not sure can be done.. or has modified the output tail shafts of an SRA to work in an IRS machine. If they had used a IRS 650 engine it would have dropped straight in as they are identical to the 750 except for the CCs...and as I look up things, the 650 cylinders were cast with a code that did have 633 in it where the 750s had 749. Good luck on this one. The engine serial number can be decoded to tell you what it came out of.

Did some more tinkering this evening. Found the rear cylinder boot from carb to cylinder was sucking, previous whoever had permatexed all around the mating surface. I planed the metal surface on my belt grinder then reinstall with o ring. Running much better now. Still has slight popping from carbs but not near as bad. Bike will actually raise front wheels off ground now and will do 60+ mph. Still not looked anymore for motor castings or serial numbers. Will look tomorrow to see what else I can find.

 

[Leadslinger_90]

Just an update if anyone was curious about this monstrosity, bike was running pretty good. Took it on a 20 miles ride with no issues. Next day… nothing… won’t fire, won’t even try. Acts like it has no compression and won’t even hit on starter fluid. Pulled plugs and am getting spark. Ok, something has to give. Pulled valve covers to check valves again and they’re out of wack. Same issues as before with the clearance issues. Pulled complete head cover to inspect further and one of the intake valves was missing retaining cups….. now I think I’m getting to the root of most of the problems. But wish me luck. this thing is liable to get torched, shot or blown up ….

 

[NMKAWIERIDER]

Good luck