MIKUNI (CHIKUNI) VM22 TUNING PROBLEMS

Saint Mason

Saint Mason

New Member
#1
#1
Hello, My name is mason and i recently purchased a coleman bt200x mini bike

I purchased a mikuni (chikuni) 22mm carburator kit with filter for it and i cant seem to get it tuned correctly......

i have not touched the needle nor have i replaced any jets. I am currently using the stock jets in it and the stock needle setting.

the bike is backfiring really bad. It also doesnt want to idle correctly.... then i noticed i had alot of fuel in my oil.

I am not very knowledgable on carburators... at all....

i currently live in missouri where the elevation is around 460 feet above sea level.

The modification i have already made to the bike are as follows

Governer removed
Torque converter
header and muffler pipe.

i have seen alot of success to these but i cant seem to get it right....

if someone could please help me with my issues i would greatly appreciate it. I am new to all of this as well.

Thanks!
 
V

VintageMoneyPit

Active Member
#2
#2
Since no one came to help and im passing by. You need to get smaller piolet jet for idle circuit the factory ones way to large.(good luck finding one that fits)
The bottom screw does fuel enrichment theres no way to lean it out enough at idle with the large piolet jet. The needle does half throttle and main jet wide open.
If you do any riding where your doing anything but wide open the chineese mikuni is a pos. Buy a real one and they perform much better easier to tune with available parts. Also put a higher stall spring in whatever clutch your using. chinuki wont idle low rpm and to get it to idle the bike will pull away at stock clutch rpm.
 
TurdFerguson

TurdFerguson

Member
#3
#3
The 22mm carburetor is too big for the set up you're running. If you go back to the factory carburetor and jet it to .036 or .037 you will see much better results from it. Or you can get a new cam (DJ-1103P CAM) and springs to make the duration of the valve longer with 26 lbs springs and that should help it too, if you dont want to go back to the factory carb. I wouldn't recommend that with the factory connecting rod and flywheel though. You'll see a big power boost from that.
 
SAS289

SAS289

Well-Known Member
#4
#4
TurdFerguson said:
The 22mm carburetor is too big for the set up you're running. If you go back to the factory carburetor and jet it to .036 or .037 you will see much better results from it. Or you can get a new cam (DJ-1103P CAM) and springs to make the duration of the valve longer with 26 lbs springs and that should help it too, if you dont want to go back to the factory carb. I wouldn't recommend that with the factory connecting rod and flywheel though. You'll see a big power boost from that.
Click to expand...
Yeah. In the current state of the engine AND a torque converter installed there is no need for bigger carburation.
 
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