Help... revs high on start up 196cc Coleman ct200

#1
Hey all
I’m new to this

I had ordered the Japanese version of the mikuni vm22 carb and installed it last week. I think I’m having some technical issues with it and need help/advice. I put it on a Coleman ct200u with a 196cc, bike is pretty much stock. Looking thru the reviews it seemed like the carb is just a bolt on upgrade with minimal adjustments. The problem with mine is it just goes to straight full Rev on start up. No adjustment I make to the idle screw/air screw/ throttle/ needle does anything. I’ve been trying to find the problem for a week now, watched hours of videos and read thru more forums then ever. I’ve checked for air leaks and reinstalled the carb twice now with no change. Gas is good, fuel line is good, throttle cable is smooth. No matter what I do it just starts and goes to full rev. Is there anything I’m missing or should do?

Any help would be appreciated
Thank you
 

Li'l Popeye

Well-Known Member
#2
Hello,
No air leaks (checked?) and goes to full rev;
If you take the airfilter off and look inside the carb, how much is the round throttleslide opened? Just a bit or can you look through the carb?
The round throttleslide can be installed in a wrong way. If it is installed in a wrong way it will not close and stay wide open.
Also; does the needle go into the brass jet in the bottom? If it doesn't it will make the round throttleslide not closing.

"Before you start your engine you should test the throttle. Depress the throttle pedal a few times and listen for the slide opening and closing inside the carburetor. If you installed it correctly you will hear the slide open and close. If you don't hear the slide moving as you are working the throttle pedal, you may have assembled it incorrectly. Remove the cap and make sure the slide is not stuck in the wide open throttle position."
 
#3
Hey thanks for a response!
Yea slide is good. I got the angled bit resting on idle screw and the slotted slide bit running up and down the little tit thing inside.

when throttle is off the slide is all the way down with a tiny gap. The idle screw adjusts the gap size.
 
#5
You must have the enrichner open. It allows additional air and fuel into the engine for starting and it will rev up sometimes enough for the clutch to engage. The brass plunger needs to be down to be off. Not sure which way the lever goes as I am out of town and can’t look at one. If that is not the problem then you must have a air leak somewhere.
 
#9
At this point I would start it with the throttle cable not attached and see if it still takes off.
if not then there you go lol
at least then you can start ruling stuff out
 
#12
Haha already been testing it with chain... otherwise it would just keep taking off on me.
It’s def something with this mikuni carb

was wondering maybe it has something to do with the governor linkage? Because right now it’s just hanging there not attached
 
#14
If it kills the engine with plunger down and runs fast with plunger up which is enrichment on turn slideadjustment in to raise slide a little at a time till it will run with plunger down one it runs with plunger down which is enrichment offthen adjust idle air bleed screw. You will have to go back and forth between idle air bleed and throttle slide height to get best idle. When you get idle correct then if it dies when opening throttle you may need larger main jet.
 
#15
Do what ole4 said and then let us know what jets you are using. Japanese vm22-133 is handle up/plunger down and handle down/plunger up for enrichment which will almost always easily run high enough RPM to take off on you. Most clones run around a 130 main and 15-17.5 pilot. When I purchased the VM22-133 it came with 100 and 30.....
 
#17
12.5 is the pilot not sure of the 30 main jet size but getting it to idle is a combination of slide height, enrichment off (warm) and idle air bleed adjustment. Main jet affects it when opening the throttle.
 
#18
Because right now it’s just hanging there not attached
You need to open the engine up and remove ALL of the governor parts. You don't want that stuff in there just spinning around way faster than the pieces were designed to. That stuff comes apart it can ruin your engine. Do a billet rod and flywheel while you've got it apart.
 
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