Chinese Mikuni 22 Idle Adjustment Screw

[Smeeneezle]

Hey, I have a question regarding a Chinese Mikuni 22 that I put on my Kart. I have a fully built 212 and the vibrations from the engine caused 3 of my bowl screws to fall out while riding. Once I got it home and took the carb off, I noticed that the idle adjustment screw had also vibrated it’s way out as well. What a bummer as I can replace the bowl screws but does anyone know where I can get a replacement idle adjustment screw for this thing? Is this something that a local hardware store (or big box store like Lowe’s or Home Depot) would carry? I guess I will be using some locktite on these once I’m able to replace them. Thanks in advance for any insight that you all may be able to offer.

 

[Li'l Popeye]

That must be a heavy vibrating engine...
You might want to try searching for Mikuni VM22-3847 Fuel Idle Mixture Screw.
Or >>here.<<

 

[Rapidrob]

You need to buy "RED" Loc-Tite thread locker. The fact that the spring loaded screw/jet also backed out is not normal at all. As stated above, something like the clutch or a driven gear,tires must be out of center or out of balance.

 

[Smeeneezle]

You need to buy "RED" Loc-Tite thread locker. The fact that the spring loaded screw/jet also backed out is not normal at all. As stated above, something like the clutch or a driven gear,tires must be out of center or out of balance.

@Rapidrob the idle adjustment screw that came in the carb wasn’t spring loaded but the replacement I’m going to have to get sure will.

 

[Havasu Dave]

@Rapidrob the idle adjustment screw that came in the carb wasn’t spring loaded but the replacement I’m going to have to get sure will.

Some things to consider: Of the thousands of these carbs used, no one else is complaining about losing the air bleeds. It's quite a few threads that have to come unscrewed to lose that thing. How far out are you setting it? If the air screw has to be turned out more than two turns for a decent idle, you should go to the next smaller size pilot jet.

The other thing I was thinking is about the bowl screws. They should not be coming out no matter how much vibration you have. This arrangement is used throughout the world on a wide variety of equipment, and has been for many years. If properly torqued, with the correct lock washers (in this case) they will not come out under any circumstances.

I note that you kept the idle jet almost unscrewed in a box stock carb set up for another fully built Predator. That bottom "jet" is just an air bleed for the pilot jet located within the bowl. You've got installation and tuning issues. And if you lost that air bleed and didn't immediately notice your idle went all to hell, you've got way too big of a pilot jet installed.