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How to balance carburetors and throttle bodies.


The conditions:

-The bike should be serviced before synchronizing the carburetors/EFI

{ Fresh oil/spark plugs/valves clearance (optional)/clean air filter }

-The engine should be at operating temperature

-You need a fuel source (a longer line or a stool to place the tank on)

-Have your service manual handy.

First, lets go with the EFI; pics and part of the text kindly provided by Josh from


I have attached pics of the throttle bodies off of my bike to better show you where the air screw is on each of the throttle bodies. 

This is the screw the manual talks about for synching the throttle bodies with a carb tuning device. 


The book indicates to synch each individually to #3 throttle body. 

How you would do this is by turning each of the air screw on #1,#2,#4 and synching them to #3. 


Example: Synchronize #1 to #3 then rev engine. Synch #2 to #3 then rev engine. Synch #4 to #3 then rev engine.

After you are done your throttle bodies should be lined up and in synch. 

Hope this helps.

May I add: Before starting the procedure, you have to disconnect the synchronizing hoses from the throttle bodies:

Use them to hook up your synchronizing tool. (Note where they go then locate the remaining tubes on the other throttle bodies)

Now with the carburetors part:

Although the procedure is provided in details into the service manual or even in the synchronizing tool owner manual,

we'll go through the procedure in a rather quick way. If you got questions about this, please come and ask your questions at:  and go in the mechanical help section.



1- Remove tank, place on a stool, hook up the extra long fuel line

2- Remove Allen head bolts and copper washers located on the motor head, below the carburetors

3- Hook up the synchronizing tool

4- Start the engine, let it warm up to operating temperature

5- Adjust idle speed (1050-1150 rpms)

You are now ready to start the procedure!

#1- Synchronize carburetor #1 to carburetor #2 (which is fixed) using the synchronizing screw located between the throttle bodies

in either direction till both read the same.

#2- Rev the engine 2-3 times to make sure all is well.

#3- Synchronize carburetor #4 to carburetor #3 using the same procedure as in #1

#4- Synchronize carburetor #2 to carburetor #3 using the same procedure as in #1

NOTE: Vacuum pressure at idling speed should be 29.3 KPa or 0.293kg/cm square or 220mg Hg; 

If you don't have a very near figure, there may be a problem with a carburetor boot or intake boot.

The difference between carburetors after synchronizing should not exceed 1.33KPa or 10mm Hg.

#5- Re-check idle, adjust in consequence.

#6- Remove synchronizing tool and replace Allen head screws and copper washers

#7- Check throttle cables slack



Maybe I'll add pics of the procedure...but its pretty graphic as is, so don't expect Digi cam wouldn't work anyways.


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