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Discussion Starter #1
Hey guys new to the forum and already hoping to get help with my 2006 Brute. Here's the back story, bought the bike used, but it ran great. Noticed a rattle in engine, took it to a shop and had timing chains put in and valves adjusted. Finally go to pick it up and it sounds great. Get on to make a quick run, bottom end is strong, then it falls on it's face, let out and it picks back up. The mechanic has checked spark through the RPM range and it appears to be firing, he swapped coils front and back, put in new plugs and still no change. He admitted to dropping the flywheel upon removal, but not sure if that would cause this issue. It ran great before this "repair" but I am at a loss. Any suggestions?

It has full HMF exhaust, and Dynatec CDI.
 

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Well if you had timing chains done on your engine,then your mechanic had just about every thing off in and around the engine area.Could be carb jetting,could be carb diaphrams,but he had no reason to play with the carbs.I would imagine the mechanic knew what he was doing,but then again your bike is'nt running right after he fixed it.You could even be off on how the timing was set up ??? I'd put my money on the timing is off or the valves are'nt set properly. I would also double check all electrical connections under the seat and on the engine...
 

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Well if you had timing chains done on your engine,then your mechanic had just about every thing off in and around the engine area.Could be carb jetting,could be carb diaphrams,but he had no reason to play with the carbs.I would imagine the mechanic knew what he was doing,but then again your bike is'nt running right after he fixed it.You could even be off on how the timing was set up ??? I'd put my money on the timing is off or the valves are'nt set properly. I would also double check all electrical connections under the seat and on the engine...
Dman I personally have never taken anything to this mechanic before now. He has been in business here for about 11 years. I questioned him about the timing maybe being off a tooth or the valves off and he just assures me that they are correct :confused:. At idle it sounds great, during take off it runs good for the first 100ft or so, then acts like it loses a cylinder. Let off and it wakes back up. He has ordered a new flywheel and waiting for it to come in and try that. I just can't see why a flywheel would cause these symptons, especially since he is telling me it has spark all through the RPM range. I also can't understand why he didn't check for weak spark or try swapping the CDI out either. But I really don't see the CDI failing by just sitting in his shop. I'm at a loss.
 

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Well if he's positive on the timing and valves,then start looking at electrical connections,fuel delivery to the carb,carb jetting - no mention on what's in your carbs and how they're set up,air leaks at air box or even carb boots.
 

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Timing would have nothing to do with those symptoms.
Check the vacuum line to the fuel pump, and all the lines on the carbs, and for actual fuel delivery. It sounds like it's running out of fuel.
 

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Discussion Starter #7
I'm really not sure as to what's in the carb. as I just bought it. It ran great before being dropped off there and having the work done. I'll definitely have him check all around the carb for lines loose and the fuel pump hose. I've read some stuff about BUS connector issues, does any of these symptoms that I'm having sound like that being a possibility?

Thanks for all the input, keep it coming.
 

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It doesn't act like the buss connector.
 

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Discussion Starter #9
Alright guys some new things to add to the list. Put a new flywheel on, no change. Running the bike with the air cleaner off, revving in neutral, when the miss occurs you can see fuel spray out of the rear carb. Removing the air box lid just moved the bogging down of the engine a little further up the RPM range. My mechanic still thinks it is dropping fire, or getting weak spark to the rear cylinder. I'm thinking it is either jetted wrong or maybe a leak at the carb holder. We have swapped coils, new plug boot on the rear, tried a different CDI, and new spark plugs. What's got me thrown is this all happened after he put new timing chains in and adjusted the valves. He is 100% certain that the timing and valves are spot on :rolleyes:. The bike ran great before he done the initial work, what's the chance that it's all coincidental?? And what's your opinions? Thanks again.
 

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Discussion Starter #10
Pulled carbs, has a 150 in front and a 155 jet in rear. Has full HMF, Dynatek CDI and K&N air filter. Does this sound right? Seems to be flooding now, so you would think bigger jets would be worse? :confused:
 

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Pulled carbs, has a 150 in front and a 155 jet in rear. Has full HMF, Dynatek CDI and K&N air filter. Does this sound right? Seems to be flooding now, so you would think bigger jets would be worse? :confused:
It worked good before it was torn down, so........... the work that was done is suspect.
These engines run like crap with the airbox off, so it's hard to go by that.
If you think it's really rich, then prop the airbox lid up a tiny bit and try it.
If you think it's lean, then open the choke up and try it.

Check to make sure that the airbox intake snorkle up by the bars isn't blocked with something.
 

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Discussion Starter #12
It worked good before it was torn down, so........... the work that was done is suspect.
These engines run like crap with the airbox off, so it's hard to go by that.
If you think it's really rich, then prop the airbox lid up a tiny bit and try it.
If you think it's lean, then open the choke up and try it.

Check to make sure that the airbox intake snorkle up by the bars isn't blocked with something.[/QUOTE]


I agree that the work done is suspect, even though my mechanic is dead set on the timing and valves being correct. One other thing that was noticed today is that when it starts the bogging, it spits fuel back out of the rear carb. Also after you shut the key off it kind of does a quick "dieseling" thing where it wants to keep running, but it's only for a split second. Nova I really appreciate all the suggestions and we are looking into them one by one. I want to get this thing figured out in the worst way. Any possibilities in it being the fuel pump or diaphragm?
 

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It worked good before it was torn down, so........... the work that was done is suspect.
These engines run like crap with the airbox off, so it's hard to go by that.
If you think it's really rich, then prop the airbox lid up a tiny bit and try it.
If you think it's lean, then open the choke up and try it.

Check to make sure that the airbox intake snorkle up by the bars isn't blocked with something.

I agree that the work done is suspect, even though my mechanic is dead set on the timing and valves being correct. One other thing that was noticed today is that when it starts the bogging, it spits fuel back out of the rear carb. Also after you shut the key off it kind of does a quick "dieseling" thing where it wants to keep running, but it's only for a split second. Nova I really appreciate all the suggestions and we are looking into them one by one. I want to get this thing figured out in the worst way. Any possibilities in it being the fuel pump or diaphragm?
The only you could see that is if the airbox lid was off, and they won't run anywhere near right with the lid off. You could check the float height in the rear carb.
I've never seen one diesel; I've seen them kick back the odd time when they're shut off.
It's acting like it's running out of fuel; bogging is usually lean, stumbling is usually rich.
 

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Discussion Starter #14
Nova we had the lid off to watch the diaphragms in the carbs. 100% correct in they will not run right with the lid off, the 650 I had was the same way. Just noticed the rear cylinder being the one bogging while the lid was off. As far as the diesel thing goes, it could be the kick back thing I assume, it just kinda sounded like it wanted to run back on itself. Is it possible the intermediate chain had it out of time enough to run OK with the jetting it had and after new chains the timing is now different and causing it to be fuel starved? What jet sizes would you recommend?
 

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I still think it's out of timing,but did you check the carb vents on the right side of the carbs and insure they are not blocked,and check the carb float levels,although they would be low from the sounds of it starving fuel in the mid range up to WOT.Also recheck the diaphrams - esspecially the rear one - insure it is sealed properly,the brass rice jet is installed, the needle is not bent, the needle retainer is set properly,and the spring is good.If the gas tank vent/check valve was blocked you would also lose power through mid to WOT.Just throwing things out there. and stock jets are #38 pilots,#152 front/#158 rear main jets,pilots set at 2 1/2 turns out. With a dynatec cdi and and hmf,I'd at least start at stock jetting,but I think you'll wind up about 1 - 2 main jet sizes higher and maybe even #40 pilots with 1 shimm under each needle.
 

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If it ran good before, please, please, please don't mess with jetting or carb tuning; that will only complicate things.
I don't think the timing being off will cause this, but you may have to check anyway.
 

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Like novakaw said before,check carb vents and fuel pump,and yes I agree about jetting - fix problem first.But it sounds like maybe the rear timing could be off by one touth.
 

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Like novakaw said before,check carb vents and fuel pump,and yes I agree about jetting - fix problem first.But it sounds like maybe the rear timing could be off by one touth.
The timing would have to be off by more than one tooth.
 

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Discussion Starter #19
Finally fixed the problem. After carb clean, and re-jet it really screams now. I really believe the initial problem was with the chokes sticking though. Just glad to have it back.
 

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Good news!
 
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