Predator 212 wont fully start

[LtDansNewLegs]

Hi All, running out of options here and am really hoping for your help. I have a predator stage 2 212cc and I can’t get it to start run for the life of me. I’ve got it to start a couple times but it won’t stay running and a majority of the time I’m getting this unique sound (uploaded video to YouTube) https://youtube.com/shorts/wRvsj3pJODc?feature=share

Carb is a Mikuni VM22 variant. I’ve tried all jet sizes from #85-125 and nothing seems to work. I’ve had the needle at the lowest setting and now I’ve adjusted it to the middle/stock setting.

I’ve spent a ton of time on the carb and literally tried every combination of settings with the air fuel screw and the idle screw. The one thing to note, Ive had it start a couple times for a second or two with the air screw almost all the way loosened out and the piston valve nearly closed.

I took the spark plug out and it was quite black and dry, so it seems to be running rich. Closing or opening the choke doesn’t seem to make a difference when attempting to star, but I have a feeling the weird sound when it’s trying to fully run, may be a indicator for you veterans to help me solve this issue.

First post here so thank you in advance for your help! -Mike

 

[panchothedog]

Put the stock carburetor back on it. If you don't have one, spend the $13-$15
to buy a new one. Many people (myself included ) have had problems with the
Chikuni carburetors. Not worth the headache.

 

[Denny]

Was the engine reassembled correctly if cam or rod was changed? Is the flywheel key in correctly?

 

[LtDansNewLegs]

I bought it used and haven’t opened or touched anything in the engine outside of the carb. It was running fine the first month I had it, until I messed with the carb. Thanks for your response

 

[panchothedog]

Well then the carburetor is the obvious problem.

 

[Denny]

I bought it used and haven’t opened or touched anything in the engine outside of the carb. It was running fine the first month I had it, until I messed with the carb. Thanks for your response

That would have been helpful to know in your first post.

 

[Master Hack]

Has anyone tried PWK carbs? Made by Keihin. I got one for a project just cuz it was cheap. I was so surprised and impressed that l put one on franken buggy. Ebay has ‘em in 20-40mm sizes.
first thing l think of when a carb change doesnt work out is, a vacuum leak. The plug reading may say different, but is it the same plug that was in when it ram?

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[LtDansNewLegs]

Thanks for the replies everyone. I just bought a used Mikuni vm22 and have the same problem as before. So I’m assuming the carb isn’t the issue? See new video https://youtube.com/shorts/QUW9aFL7TcU?feature=share

 

[LtDansNewLegs]

Put the stock carburetor back on it. If you don't have one, spend the $13-$15
to buy a new one. Many people (myself included ) have had problems with the
Chikuni carburetors. Not worth the headache.

Thanks for the feedback. I just bought a used Mikuni and am still having the same issue with the same start up experience. It starts for a quarter of a second that chokes and dies. Uploaded a new video showing the Mikuni carb and the same exhaust/engine response https://youtube.com/shorts/QUW9aFL7TcU?feature=share

 

[BaconBitRacing]

Thanks for the feedback. I just bought a used Mikuni and am still having the same issue with the same start up experience. It starts for a quarter of a second that chokes and dies. Uploaded a new video showing the Mikuni carb and the same exhaust/engine response https://youtube.com/shorts/QUW9aFL7TcU?feature=share

Pick up a stock carb. Probably a fuel mix issue. Guys, am I correct? As Master Hack said, vacuum leak is an option.

 

[panchothedog]

Sounds like he doesn't want to listen. Runs fine for a month, puts on a Mikuni,
won't run, so puts on a 2nd Mikuni, still won't run. OBVIOUSLY it's not the
carburetor. PUT the stock one on, drive your kart or bike and have some fun.
QUIT banging your head into a wall. It hurts after a while, and if you aren't careful it can even cause you to become STUPID.

 

[Master Hack]

I‘ve been around a while, had a few experiences here and there, and l have concluded nobody sells good used carbs. Why would ya? If it works well, why sell? Then when its off the machine how do you know?
l guess l’ve been hosed enough to be cautious and l’m just a cynical old f**k anyway.

 

[Master Hack]

What size carb is a stock carb? Maybe the carb is too big for the engine?

 

[LtDansNewLegs]

Bought a stock carb and can get it to start occasionally but won’t last long.

The biggest thing I’ve noticed is that theirs gas spewing out of the carb when I’m pulling the starter and then you can literally see the gas sitting inside the carb. The only thing I can think of is the stock carb jet size may be too big? Potentially because of the stage 2 modifications and governer removal(bought it that way)?

This is my first kart so I’m not a veteran and appreciate your patience with trying to help me. I’ve adjusted the AF mixture screw all the way out to make it as lean as possible but it’s not fixing the problem. Even though the carb is brand new, I cleaned it and it helped a little, but can’t get it to stay running.

Edit: Took the spark plug out and it had some gas on it. How the heck do I make this engine runner leaner to fix the problem?

 

[BaconBitRacing]

Now this is a stumper for me. Engine experts I call on you!

 

[LtDansNewLegs]

Happy to record and upload a video if it helps

 

[panchothedog]

The stage 2 modifications (whatever they are ) are going to require more gas not less than a CORRECT stock carburetor can supply. So your statement of maybe stock carburetor jet size is too big, makes NO sense at all. When you modify an engine and leave the stock carb on it, it is necessary to install a BIGGER jet so it will run correctly. You said that it ran great for a month until you put on a Mikuni. Where is the carburetor that was on it that first month when it was running fine. If the current NEW carb is spitting gas when you pull it over, it can only be one of two things. Either the carburetor is WAY too big, or the valve train is not in sinc with the piston which can only happen by someone moving the cam in its relationship to the crankshaft. I have never heard of a tooth breaking off of the cam or crankshaft gear, but I suppose that it is not impossible. Maybe open it up and check.

 

[LtDansNewLegs]

The carb the first month when it was running fine was in the first video I posted. I figured something happened so I tried a Mikuni. You highly recommended I go w a stock carb so I did, and that is where I’m at now.

The carb is stock now so I don’t see how it is too big like you pointed out first.

In regards to the valve train, I’m not sure how that would allow the carb to flood with gas, but like I said previously, I’m not a small engine expert. Having said that, If my carb is flooding with gas when I check inside after pulling a couple times, and spewing gas out when I’m pulling the starter, I’m not sure how that wouldn’t indicate something internal to the carb is allowing to much gas to flow. Again, I’m no expert, but I’m thinking with what I know.
Thanks for the feedback

Edit: I have not touch the internals since buying it. Although it’s not internal, I lubed the clutch bearing with white lithium grease from another recommendation online, and that’s it outside of the carb and installing the throttle plates when going from a Mikuni to stock carb.

 

[Denny]

Sometimes diagnosing these things is a process of elimination. We don’t have crystal balls to be able to see all that was done to the engine. We don’t know how it was maintained, beat on or if something had just plain old broke. Start by pulling the valve cover and and check for bent or broken pieces. We are not there we can’t fix it for you.

 

[LtDansNewLegs]

I’m going to open it up and check the internals. Thanks all.