I'm going to blow it up- I'm so fed up with this thing I'm shaking while typing!

So- I took the day off to spend on the trails- up early, packed my 2-up with food & water, headed out to the shed to warm the 05 Brute 750 with only 170 pampered miles on it- choked it, started and sounded beautiful. Let it run a good 5 minutes, shut the choke off, the idle dropped to a nice even mellow tone...

Perfect- put the helmet & goggles on, threw her in drive and opened it up.....

I got 10 feet before it started backfiring. It idles perfect, if I give it a little gas, the rpm's go up a litlle and it seems ok- a little more gas and it bogs right down So I threw some dry gas in to see what would happen... no better.
The gas is 1 day old high-test. I spent the next 6 hours removing the twin carbs and going through them- they were clean. I pulled every jet, cleaned every hole and reassembled.

Started up and idled perfect, as soon as I blip the throttle, bogsville! As soon as it hits mid to high rpm, it starts to backfire through the carb. If I just pin the throttle wide open, it surges to high rpm, backfires and almost stalls, but wont, it'll just keep cycling like that with the throttle pinned...
The plugs are only a few weeks old

Any help on this one guys

 

Is this the first time you fired it up and went for a ride with the new plugs? If so, I would try out the old ones if you have them just for comparison. I had a new set of plugs put in my truck and then my 8 cylinder felt like a 6 cylinder with a banging rattle. They took them out and discovered cracks in the insulators. New plugs and runs like it should. Just a guess. You've already done the carb. route.

 

No- ran fine yesterday. I hit it with the hose and put it in the shed. sat there until this morning.

 

Is there water in the airbox? I've heard some people complain about the intake design on the Brute. See if the filter is wet or dry.

 

The OP just spent 6 hours removing, cleaning & working on the carbs... I would think he would have checked it.

Well, it sounds like too rich condition. When you were working on the carbs, have you checked to make sure the choke (actually fuel enrichener) plungers are opening and closing all the way when you move the choke lever? There is one for each cyl, one for front and another for rear. If it hangs open a bit, it would squirt in extra fuel into the carbs and make the engine bogging when you open the throttle, but would not kill it. That's a typical symptom of too rich. Just to test, ride with the air box lid open. If the quad runs better like that, it is confirming that engine is running too rich.

 

If I engage the choke- the rpm's raise quite a bit, no backfiring issues with the choke. When I disengage the choke, the rpm falls to an even idle. I just pulled the coil lead on each cylinder and ran it on one cylinder to see what happens- same. Water in the box was never an issue- always dry.
The "enrichener" valves are such a PITA to get to, I was careful putting them back in, and given the high rpm when I engage the choke, I'd assume they are seating properly.
I removed all the connectors under the seat and used compressed air to dry them. I put a heat gun on the rev by-pass button on the handle bar to dry it out- thinking maybe moisture was shorting it... no change.

Now, the belt light is blinking (wasn't before) so I'm going to search the forum to see how to reset this. I pulled the belt cover off.

The motor sounds like it's rpm's are being limited. Just like if you try to back up too fast without using the bypass- it just pops, bogs & backfires.

 

Well- I just reset the belt- didn't change anything. I guess it's off to the kawi dealer- and a god knows how mush $$$.

 

Mine did the same thing as yours. After hours of cleaning the carbs it turned out to be the seal around the air box lid. The little rubber seal on top of the air box that seals the lid air tight was worn. Put on a new seal ($5) and it hauls a$$ once again!!! Yours might be fine but be sure to check it out before taking in. A friend had one this weekend that was sluggish, not popping like mine but just a little loss of power, his seal was missing all together. Put on a new seal and it ran like new!!

 

that's strange- I've run mine without the airbox lid on and it ran fine (before this incident)

I'll just let the dealer handle it- I'm fed up with the darn thing- entire day spent trying to figure it out when I should've been on the trails- just completely disgusted with my kawasaki right now.

 

polsports-

I may owe you a six pack if you ever come to mass-
Thinking about what you said with the cover, it occurred to me that the whole day, after I tried fixing everything, I never put the cover back on. So I just went out to the shed- put a little silicon around the airbox cover, started it up- it was rough with a little popping when I bliped the throttle for the first 30 seconds in neutral, then it cleared up. I put it in gear and took it for a ride around the yard- it rips! Pulling the front wheels right up....WTF

I'm holding you responsible for my lost day of riding- you should've read this thread sooner. It's all your fault