Synchronisation d'une BMW R1200GS avec le dépressiomètre TwinMax

BMW R1200

Here is a quick tutorial on carburetor timing for a BMW R1200. This tutorial is also valid for the R1100 and R1150 series except for the idle timing which is different.

Note that on the R1200, the idle speed is controlled by the electronic control unit via stepper motors. These motors can be calibrated using the GS-911 tool, so it is not possible to adjust the idle speed manually.

Caution: Synchronisation only takes a few minutes when you are used to it, but the first time it may take a little longer. So remember to work in a sufficiently ventilated workshop so as not to be bothered by the exhaust fumes.

Installing the TwinMax on a BMW R1200

First, make sure the bike is at normal operating temperature, normally 10 minutes of riding is enough to reach this temperature. It is also best to perform the synchronization after setting the valves to get finer results.

On the right hand carburetor, fit one of the Twinmax hoses to the vacuum port after removing the rubber cap.

On the left hand carburetor you will have this hose or a rubber cap with a vacuum port as on the right hand carburetor. Place the second hose of the Twinmax on it.

Here is a picture of the installed Twinmax hose.

For this synchronisation, I disconnect the ECU and thus neutralise the stepper motors. There is no rule, some say this is the right way to do it, others assure that the stepper motors do not influence the dynamic synchronization. I have personally used both methods and have not been able to detect a clear difference.


Synchronisation of the BMW R1200 at idle

With the engine off, I set the Twinmax to maximum sensitivity and then make sure the needle is centred.

I then start the engine and check the timing at idle. The needle of the display oscillates by 1 scale around 0. This is normal, if the needle of the display oscillates around another value than 0, I advise you to bring your motorbike to a competent BMW dealer.

Dynamic synchronisation of the BMW R1200

I perform the dynamic synchronization with the Twinmax in order to check the good balance at 2000, 3000 and 4000rpm. If the Twinmax needle doesn't stay on 0 then I adjust the cable settings. 

Cable adjustment

Adjusting cable slack is tricky on the R1200 because you can't feel the "slack".

The only way to do this is to plug in the Twinmax and loosen the cables. Then tighten one side until you see a reaction from the Twinmax and then continue for about a lap. Then do the same on the other side until the Twinmax is balanced. At this point you should have about 1mm of slack.

I would stress that you need at least 1mm of slack in the cables before you start synchronising and never adjust one side so that all slack is removed. If you remove the slack, put it back in and adjust the other side to synchronise.

Using a 10 mm open-end spanner, I loosen the locknut and then adjust the cable by hand using the knurled nut.

Now I use two spanners to tighten the lock nut. I just tighten it to adjust and check my timing again. Be careful, it's easy to tighten the nut and remove the sync.

Here is a close-up of the keys.

Note: Sometimes it is difficult to tighten the nut and keep the timing exact. To do this, I tighten the nuts, then use a pair of pliers and gently turn the knurled nut (on the R1100 / 1150) to get the exact timing. Then I tighten the locknut to 4nm (slightly).

A final check of the timing from 2500 to 4000rpm, and that's it. Remove the Twinmax hoses, reinstall the rubber plugs and/or hose, and roll!!!

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