Tech Tips!

by Jonathan Teraji

20 MM Round Slide Carb

The following pictures and text should take some of the mystery out of the 20mm round slide carb.

There are also cleaning and set up tips.

20mm round slide carb from Mikuni.

Flange Mount

The two vent tubes are shown, and these should vent to atmosphere. They do not attach to anything.


This is the other side of the carb. You can clearly see the flange mount and the rubber o-ring that seals against the spacer on the manifold.








This is the manifold that is required for use with the 20MM carb. Although it looks similar to the stock manifold, it is not the same. This manifold can be used with oil injection or without.



Close up showing the location of the choke, fuel inlet, idle screw, air mixture screw, and access to main jet.

The choke is a pull out for on, and push in for off.

Adjust idle to your preference

Turn Right = increase

Turn Left = decrease

The Air mixture screw is shown with an arrow, and is set at 1 1/4 turns out.


Main Jet access is easy! Use a 10mm wrench and undo the bolt. The main jet is at the end of the bolt you remove!


View of Float Bowl


Bottom of Carb with the float bowl removed.

Shows location of the pilot jet and needle receiver.

Needle receiver should be removed with a 8mm wrench, and the pilot jet with a small flat blade screw driver.

Remember, these jets are brass and are easily destroyed.

When cleaning carb the pilot jet should be removed and "reamed out" with a fine wire. Carb cleaner will not remove the crud in the pilot jet!


The needle receiver unscrews and comes out the bottom of the Carb.


This is the needle receiver and the 3 bleed holes that get plugged up after bike sits for a long time.

There are more bleed holes on the other side. These holes need to be cleaned by "reaming out" with a fine wire.

Carb cleaner does not do the job.


When removing the cap this is what you will find.

Two items of importance....

The needle, (clip is set on third slot down from the top) and the keeper.



So that's the basic deal. If you suspect carb problems, take it apart and clean it.

Try not to change the float level. The quality of the Mikuni Carbs that we sell is such that the float level is always right.

If you clean and reassemble the carb properly, and the carb is set up as suggested on the right, and the bike is still not operating properly, it is probably not the carb!

 Clip......................................3rd from top

Idle.................................your preference

Air Mix....................................1 1/4 turns out is

Main Jet........................170, 175, or 180

Pilot is 



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