How to tune your VM22 Mikuni clone carburetor for Predator 224 and Predator 212 engines.

https://www.amazon.com/ORAEVYPerform... Carb and kit I used in this video. Fuel used: gasoline PDF file for the VM22 carburetor. There are only a few issues you may run into outside those described in the pdf and I've tried to cover them in the video by demonstrating the issues and how to correct them.

https://commons.princeton.edu/wpcont...

Great Source of info!

‪@bahnzai7313‬ shared a great tip to remove/install the eclip. It works!

First Prepare the VM22 Mikuni clone carb before you install it on the engine:

MAKE SURE CARBURETOR IS INSTALLED AND ALIGNED CORRECTLY WITH NO VACUUM LEAKS

1. Main jet size:
Example for gasoline, I'm at 650 feet above sea level, the base starting point on jet size here is to install a 120 to 135 main jet. This is normally rich. Start with a rich condition and lean out the air/fuel mixture a little at a time. Most of the VM22 Mikuni clone carburetors will come with a 95 or 98 main jet. Obviously those main jets are way too small. Find out what altitude you are currently at and adjust your jet size accordingly. At sea level you'd probably want to begin with a 130 to 145 main jet. If you're at higher elevations of say several thousand feet, you may want to begin with a 110 to 125 main jet. This is just a rough starting point for gasoline and it's intended to be rich. You can lean it out 1 size at a time to get the mix where you need to be.

2. Pilot jet size:
The pilot jet is very forgiving. There will be some variation for altitude but the engine is not moving much air at idle, so this will let you get by with a general setting that works for multiple altitudes. The VM22 carburetors I've purchased have had different pilot jets installed. I like to go with a # 20 pilot jet here, but I've purchased a few different sizes to keep on hand. You should be fine with most pilot jets from # 18 up to around a # 26. A pilot jet within this size range will be adequate for most elevations for most mild engine builds. Of course if you have a fire breather on your hands, you'll likely need more pilot jet.

3. Float level: *Spring loaded needle valve
The float level will be wrong on your new VM22 Mikuni clone. It needs to be readjusted properly before installing the carburetor. Hold the carburetor upside down with the float bowl removed. You'll need to bend the float adjusting tab that sits directly above the needle valve. The needle valve is spring loaded, when you press down lightly on the float and release, you'll see the float spring back up a small distance. Adjust the float by bending the tab until the float is only level when you apply light downward pressure on the float. (overcoming the spring in the needle valve) When the float does not have light downward pressure applied it should spring up slightly,
*IMPORTANT* only with light downward pressure should the float appear to be level.

Once you have your VM22 Mikuni clone carburetor prepared for a first run, turn the brass pilot adjustment air screw on the underside of you carburetor in gently until it just stops. Don't force it, then turn it out counterclockwise 1.5 turns and stop. This is where you want to begin and hopefully end.

Start the engine, allow it to warm up, adjust to a low idle. Turn the brass pilot adjustment air screw out 1/4 of a turn. Wait a few seconds, listen to the idle speed of the engine. If it increased, keep turning the brass pilot air screw out another 1/4 turn, listen to the engine. If it slows RPM, try 1/4 turn in, and listen to the idle speed. When it's adjusted so the idle speed neither increases nor decreases, STOP. Turn off the engine and count the number of turns to close the brass adjustment screw. You are counting the turns in so if all is good you can put it back exactly where it was.
How many turns in will determine your pilot jet size. More than 2 full turns to close the adjustment screw, your pilot jet is too large. Less than 1 full turn to close the adjustment screw, your pilot jet is too small. Rejet and repeat. To me the perfect setting is 1.5 turns out for gasoline.

Main Jet: Tune under a load. While riding, pull to full throttle, release the throttle and listen to the exhaust during deceleration. If your jet is too lean, it sounds like firecrackers, increase one jet size at a time until it doesn't. If your exhaust does not crackle and pop during deceleration during set up. Reduce the main jet one size at a time until it crackles and pops during quick deceleration from full throttle, then increase one jet size. Read the Sparkplug. White=lean, black=rich, brown=perfect.

#mikuni #predator212 #kartracing