Hello all. Got one of my KMZ 150's running with a simple carb cleaning thanks to the info. I was given from here. Hopefully one or all of you can help me with the other one because as the title says, I'm stumped ! The problem is in acceleration. The atv idles fine but when given a little throtle it falls on it's face and dies. First off let me say that I know the problem in solely in the carb. because I can take the carb off the other atv, install it on this one and it runs like a top. Upon further investigation I noticed that the slide ( this is a constant velocity type carb.) does not function normally. If I remove the air cleaner hose and watch the slide with a mirror and flashlight I noticed that it does not move when I accelerate causing the engine to die, however if I reach in with my finger and raise the slide while I accelerate then I can rev the engine to max rpm's with no problems. If operated by hand the slide appears to operate smoothly. I completely disassembled the carb and soaked it and the jets in carb cleaner all night, ran a fine wire thru all small holes in all jets, rinsed with gasoline and blew out with compressed air, and allof this I've done twice. Checked the diaphram by gently stretching it over a mini mag flashlight but found no holes or tears. The two holes in the bottom of the slide are also not obstructed. Any other suggestions as to why this thing won't create enough of a vacuum at the top of the diaphram to riase the slide would surely be appreciated. I'm all out of ideas! Also, does anyone know what brand of carb.s these are on these Redcats? It might help in obtaining a rebuild kit. Thanks, Jeff

 

Welcome to the forum 3910, I am not sure what to suggest to you. You seem to have covered all the basics and then some. My first thought was a vacuum leak, but the other quads carb solves the problem. Have you taken the carbs apart next to each other to see if they truly are identical?

 

you probably have a pin hole in the diaphram not allowing it to create vacuum to move the slide up, their's no parts available( except jets), for these carburators, you need to replace it. costs runs from $45.00-$100.00,

 

Good idea bill2099! [img]i/expressions/face-icon-small-smile.gif[/img]

3910 you can check it out by trying the good diaphram in the bad carb.

 

OK. It appears I've looked at most everything but I'll try swapping diaphrams, maybe, not sure what it's worth since I can't just buy a diaphram. Does anyone know where a guy could get a name brand replacement carb. for one of this ? Might cost a little more but at least the next time I could rebuild it. Thanks

 

I was just trying to eliminate items in question.

John at Raceway has a mikuni replacement for the 150 I believe.

 

3910,

Does your CV carb have the automatic choke?
This could also be part of your problem.

Do you have a replacement carb in mind?

Will there be enough clearance to mount the new carb?

Just some things to think about.

Don't know if it helps.

Some carbs to think about for replacement:
Mikuni TM24
Mikuni TM28
Mikuni VM28

Things to consider when replacing the carb.

Jetting
Placement and clearance for Carb
Throttle Cable
Air Flow (Possible MOD for new air filter)

Run a search for best price on these carbs.

Good Luck.

 

hey smb05 i like to know how the automatic choke makes the slide not work, isn't the slide operated by the diaphram? which in turn is operated by vacuum???

 

Again, it was just a thought for him to look at. My 150 has the manual choke. It also runs off of a vacuum line and a manual choke cable. And if I'm not mistaken the automatic choke runs the same way with the vacuum line and the automatic choke control module. But again it was just a thought. Let me ask you this. What is the vacuum line that connects to the top side of your carb? What does it operate or what circuit does it effect? Here's another question. What happens if the choke is stuck open or partially stuck open? What kind of drivability issues or symptoms would you have?

There are so many things it could be. Pin hole so small that it's undetectable, vacuum leak around intake, needle bent or not true(rubbing or binding), Slide rubbing or binding, the list goes on and on. There is also another diaphragm to look at located towards the top of the carb connected by a vacuum line(operates in conjunction with choke circuit) that will give drivability problems if there is a vacuum leak with that diaphragm. But again who am I, just someone with thoughts and ideas. Please correct me if I'm wrong. I like to learn new things everyday.

Thanks for any additional input and information.

SB.

 

3910, was it the diaphram? I was looking at a spare carb I have for my KMZ 150 - (ordered an electric choke under warrantee and was sent a whole new carb)- the throttle cable operates a typical butterfly valve but that slide your talking about must operate some kind of metering jet? Does that slide work by the engines vacuum? I am used to the Mikuni slide type carburetors where the slide is mechanical. Let us know how you make out. I'm curious on how these carbs work.