Synchronisation d'une Yamaha XTZ 1200 avec le dépressiomètre TwinMax

Yamaha XTZ 1200

Le moteur de la Yamaha XTZ 1200 désynchronisé va présenter plusieurs symptômes :

  • An unstable idle,
  • A slower rise in speed,
  • Vibrations,
  • Holes during acceleration,
  • Increased fuel consumption.

Synchronization is the last step in an engine tune-up, after valve lash adjustment, air filter change, and if necessary, ignition timing and carburetor adjustment.

Throttle cables must also be in good condition and have sufficient grip clearance, or must be changed before synchronization.

Before synchronizing the Yamaha XTZ 1200

I advise to have a spare air filter before starting. The one on the XTZ1200 should normally be replaced every 37,000 km, but in very dusty conditions, its life can be reduced by half. 

  • First, remove the seat.
  • Then, remove the 2 plastic side covers on each side to give access to the screws that hold the tank.
  • We can also drill the 2 covers to give access to these screws more quickly without removing the covers.
  • Then, you have to free the 2 event and overflow pipes from the tank to allow you to rotate the tank towards the back without pulling on the pipes.
  • Once the 2 side screws are removed, the tank can pivot. I use a board to hold it in the raised position.
  • I advise at this stage to empty the small drain of the air box which probably contains a little oil (put a rag underneath).
  • Put the metal clip back in place afterwards.
  • We have now access to the air box.
  • To reach the filter, remove the screws without forgetting the one which is hidden under the central cap.
  • After reassembling the filter in its housing (tightening the screws to 1.6 Nm), we can now focus on the synchro.
  • The plugs are located on the injector bodies on each side. On the left side, it is a small hose that must be removed during the first synchro.
  • To remove the hoses, there is no need to pull hard. By doing so, the hose is lengthened, its diameter shrinks and it becomes more difficult to remove, with the risk of causing cracks or even breaking it.
  • You just have to take a flat screwdriver and push the end of the hose which then comes out very easily. On the left side, there is a vacuum outlet closed by a small plug.
  • For the next step, you need to get a "T" connector and a plug.

Yamaha XTZ 1200 injectors synchronization

  1. We are ready for the synchro... I use a TwinMax because I have it since a long time for my Flat Twin engines. Be careful with home made depressiometers, made with a plastic tube: it can be suitable but you will have to use a very small inner diameter tubing to have a good reading accuracy.
  2. Now simply plug the TwinMax's A-tube into the left vacuum port and the B-tube into the right port.
  3. The TwinMax is calibrated: switched on, sensitivity at minimum.
  4. With the " Zero " button, we make sure that the needle is centered on the " 0 " position, and we increase the sensitivity to the maximum, correcting with the " 0 " button so that the needle remains in the central position at " 0 ". Then decrease the sensitivity to the minimum.
  5. Start the motorcycle (ideally, the synchro is done on a warm engine. The above operations should therefore be done on a warm engine, which should be allowed to warm up a little when adjusting)
  6. We leave it at idle, and we look at our needle: it should theoretically remain at " 0 ". Then we slowly increase the sensitivity to the maximum. The needle must remain at " 0 ". If it is not the case, we go to the next step.
  7. Then, we redo the same test but accelerating to 3000 rpm.
  8. If the needle shifts to the right or left, the injector bodies must be synchronized.
  9. One of the 2 injectors has its adjustment screw painted in white. This is our reference. YOU MUST NOT TOUCH IT. On the other injector, the same adjustment screw exists, it is it which will have to be adjusted.
  10. We screw or unscrew until our needle is centered on the "0". After each adjustment of the screw, we let the gas pedal return to its closed position and we open again. Several tries are often necessary to reach an optimal setting.
  11. When it is finished, we put everything back in place (DO NOT FORGET THE 2 DEPRESSION PLUGS) and it is finished.

Little trick on the synchronization of the injectors of a Yamaha XTZ 1200

There is a possibility to extend the vacuum hoses by adding a longer hose (connected to the "T" on the left and to the vacuum hose on the right), which allows to make a synchro without dismantling anything.

On the other hand, on a fuel injected motorcycle, it's rare that the synchro goes out of order, so I would recommend to check it if you feel the symptoms of a misaligned engine or every 20 MKM.


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