TwinMax I Carburetor Synchronizer

Honda Transalp

Honda Transalp

The site is a reference site for all Honda Transalp owners. You will find tons of useful information and also a tutorial on carburetor synchronisation using the TwinMax.



This operation should be carried out when the motor is at its optimum operating temperature.

  • You must have previously adjusted the valve clearance (cold engine).
  • The air filter must be clean (or new).
  • The spark plugs must be clean (or new).
  • The carburetor settings must have been adjusted.

The required equipment is as follows

  • 8, 10 and 12mm spanners or sockets
  • Phillips screwdriver size 2
  • Flat screwdriver
  • Lighting
  • Twinmax 

Preliminary disassembly

  • The meter cover (4 Phillips screws)
  • Front panels (2 Phillips head screws)
  • Rear panels (2 Phillips head screw)
  • The seat
  • The tank


The vacuum reference value is set by the left carburetor (that of the rear cylinder). The carburetor timing adjustment screw is located between the 2 carburetors.

The screw is integral with the "rudder" (blue arrow) that controls the lifting of the left carburetor (rear cylinder), which is controlled by the throttle lever via the accelerator cables.

The right carburetor ball lift control "rudder" (yellow arrow) is attached to the control plate (front cylinder red arrow and red dotted line).

When acting on the adjusting screw, the right carburetor rudder is lowered or raised, which causes the right carburetor ball to be raised or lowered via the control plate (red dotted line).

The vacuum thus created by the front cylinder acts on the vacuum gauge.

The vacuum gauge calculates the difference in vacuum between the 2 cylinders and displays it on the measuring dial.

Synchronisation is considered to be good when the difference in vacuum between the 2 cylinders tends towards zero.



With the engine running, using pliers (wooden clothes pliers, vice pliers, framing pliers, etc.), pinch the vacuum hose from the petrol tap.

Disconnect the petrol valve vacuum hose from the rear cylinder vacuum port.

Leave it running, the motor must not stop. If the engine stops when the carburetors are empty, it means that the clamp has not been placed correctly, reconnect the hose and start again, otherwise stop the engine.

Left side of the engine

Unscrew the vacuum connection nipple from the rear cylinder (Pay attention to the sealing washer).

Screw in the Twinmax nozzle instead (2 x 5mm nozzles to be ordered at the same time as the Twinmax) Connect the tube from socket "A" of the Twinmax to this nozzle.


Right side of the engine

Use the cross-headed screwdriver to remove the vacuum intake screw from the front cylinder. (Pay attention to the sealing washer).

Screw the end cap of the Twinmax in place

Connect the hose from socket "B" of the Twinmax to this connector.

With the engine still off, calibrate the Twinmax as follows :

  • Switching it on
  • Set the sensitivity button to "MAX".
  • Using the "ZERO" button, set the hand to "0" on the dial.
  • Reset the sensitivity button to "MINI".

Reverse the tank so that the passage through the air ramp between the carburetors and the air box is free.

Through this hole, you can adjust the synchro with a long flat screwdriver.

Start the engine and keep it at high idle using the idle adjustment wheel (approx. 2500 rpm).

The most difficult part is to place the screwdriver on the adjusting screw: help yourself with the lamp to locate it, the rest is a matter of "feeling". Personally, I worked from the right side of the bike, it seemed to me that I could "see" the adjustment screw better.

Screw or unscrew this screw to bring the pointer closest to the "Zero" of the dial with a possible equivalent travel on either side of the zero if the rpm is not high enough.

Increase sensitivity to fine-tune the setting. Sometimes you may need to increase the idle speed.

Do not press down on the screwdriver when adjusting because by pressing down you will make a wrong adjustment (the screw is on the "transmission link" between the two carbs so when you press down you increase the lift of the bushes).

Lower the idle speed to its optimum position (1300 rpm +/- 100) using the idle adjustment wheel.

Switch off the engine and carry out the various re-assemblies, that's it!