TwinMax I Carburetor Synchronizer

Yamaha XTZ 1200

Yamaha XTZ 1200

PREAMBLE

An out-of-sync motor will have several symptoms:

  • Unstable idle,
  • Bad Rise in speed,
  • Vibrations,
  • Increased fuel consumption…

Caution: Synchronization is the last step in engine tuning, after valve adjustment, air filter change if necessary, and if necessary, ignition timing and carburetor adjustment.

The throttle cables must also be in good condition and have sufficient clearance at the grip, or must be changed before synchronisation.

This synchro information applies of course to all motorbike models, with carburetors or injection.

In the case of a 3- or 4-cylinder, simply choose a reference cylinder (normally the injector body must be identified) and synchronise the other injectors from this reference.

 

BEFORE SYNCHRONIZATION

I recommend having a spare air filter before starting. The XTZ1200's air filter should normally be replaced every 37,000 km, but in very dusty conditions its life can be cut in half.

01
First, remove the saddle (not too difficult to start with...).
02
Then remove the 2 plastic side covers on each side to give access to the screws holding the tank. You can also drill holes in the two covers to give access to the screws more quickly without dismantling the covers.
03
The 2 overflow and vent hoses must then be released from the tank to allow the tank to be pivoted backwards without pulling on the hoses.
04
Once the 2 side screws have been removed, the tank can be rotated. I use a board to hold it in the raised position.
05
I advise at this stage to empty the small air box purge which probably contains some oil (put a cloth underneath). Put the metal clip back in place afterwards.
06  We now have access to the air box. To access the filter, remove the screws without forgetting the one hidden under the central cap. After reassembling the filter in its housing (tightening the screws to 1.6 Nm, so no tightening like a dumbass...), we can now concentrate on the synchro.
07
The sockets are located on the injector bodies on each side. On the left side, it is a small hose that has to be removed during the first synchro. For the removal of the hoses, there is no need to pull like a patient to remove them. By doing so, the hose is lengthened, its diameter narrows and it becomes more difficult to remove, with the risk of causing cracks or even breakage. All you have to do is 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 socket closed by a small plug.
08
For the next step, a "T" connector and a cap must be purchased (auto parts shop).

FUEL INJECTOR SYNCHRONIZATION

We're ready for synchro... I use a TwinMax because I've had it for a long time for my Flat Twin engines. Beware of home-made pressure gauges made with a plastic tube: it can be suitable but you will have to use a very small inner diameter tube to have a good reading accuracy.

01
Simply plug TwinMax tubing A into the left-hand vacuum socket and tubing B into the right-hand socket.
02
Calibration of the TwinMax is carried out: switch on, sensitivity at minimum.
03
Using the "Zero" button, make sure that the needle is centred on the "0" position, and increase the sensitivity to the maximum, correcting with the "0" button so that the needle remains in the central position at "0". The sensitivity is then reduced to the minimum.
04
Starting the motorbike (ideally, synchro is done on a warm engine. We should therefore do the above operations on a warm engine, which we will let warm up a bit when we adjust the engine), leave it at idle and look at our needle: it should theoretically stay at "0". Then we slowly increase the sensitivity to the maximum. The needle must remain at " 0 ". If this is not the case, we move on to the next step.
05
Then the same test is repeated, but with an acceleration to 3000 rpm.
If the needle shifts to the right or left, the injector bodies must be synchronised. One of the 2 injectors has its adjusting screw painted white. This is our reference. DO NOT TOUCH IT. On the other injector, the same adjusting screw exists, it is the one that will have to be adjusted.
06  Screw or unscrew until the needle is centred on the "0". After each adjustment of the screw, we let the accelerator return to its closed position and reopen. Several tries are often necessary to reach an optimal adjustment.
07
Screw or unscrew until the needle is centred on the "0". After each adjustment of the screw, we let the accelerator return to its closed position and reopen. Several tries are often necessary to reach an optimal adjustment.
08
When it's over, put everything back in place (DO NOT FORGET THE 2 DEPRESSION PRESSURE PLUGS) and that's it.

SMALL TIP

It is possible to extend the vacuum hoses by adding a longer hose (connected to the "T" on the left and to the vacuum outlet on the right), which makes it possible to make a synchro without disassembling anything.

On the other hand, on a fuel injected motorbike, it is rare that the synchro goes out of sync so I would recommend checking it if you feel the symptoms of an out of sync engine or every 20 MKM.