TwinMax I Carburetor Synchronizer

BING 40mm Carburettors

BING 40mm Carburettors
Balancing 2 BING 40mm carburetors of a BMW flat twin in 3 steps and using the TwinMax carburetor synchroniser
 
ADJUST THE IDLE RICHNESS
 
01
Warm up the engine for a good 20 km if the start is cold, less if the engine is lukewarm to warm it up.
02
Use a screwdriver to adjust the carburetor by carburetor idle richness screw.
03
Disconnect the right-hand spark plug wire and insert a spare spark plug whose base (ground) touches the engine/chassis ground (to avoid bursting the high-voltage coils).
04
Go to the left side of the bike and start the engine, which should still be at operating temperature.
05
Turn the idle richness screw by "screwing" and then "unscrewing" slowly, until the idle speed stabilizes and you can hear the engine.
06 When the maximum engine speed for the cylinder being adjusted is reached, turn back 1/8 turn (unscrew).
07
The richness is perfect on the left, stop the engine (turn off the ignition with the key so as not to slam the HV coils).
08
Repeat exactly the same procedure on the right side of the engine.
09
The richness is perfect on the right, stop the engine (turn off the ignition with the key so as not to slam the HV coils).
10
Reconnect the HV cables correctly to the motor coils.

 

SET THE SYNCHRONISATION TO IDLE

01
Unscrew the vacuum screws located under the 2 carburetors (for me Bing CV 40mm).
02
Connect the two Twinmax tubes to the inlets previously blocked by the two vacuum screws.
03
Switch on the Twinmax and set the needle offset to "0" using the two buttons on the housing (button 1: offset / button 2: sensitivity). The result of this step will determine all future settings. The needle must be centred at "0" (motor off) and the sensitivity of the instrument at max.
04
Start the motor (which must still be at its operating T°) and reduce the sensitivity of the instrument to 3/4 of the maximum (sufficient for good adjustments).
05
Once the idle speed has been established, the needle should normally deviate more or less to the right or left.
06
Choose ONE first carburettor and play on the idle screw to bring the engine speed to around 800-900 rpm, even if this disturbs the synchronisation even more.
07
Act on the second carburettor and play on its idle screw so as to bring the needle of the Twinmax spark gap back to "0". The needle moves a little with the engine pulsations, this is normal and this is what makes the first attempts to adjust the synchronisation a little difficult.
08
If at the end of the idling synchronisation the engine speed has stabilised at around 800 rpm (no less!) then you have made it!
09
Otherwise, start again from step 6 by raising ONE SOME engine speed. This will of course disrupt your synchronisation but by acting on the second carburetor you will find the ideal setting for stage 8.
10
Switch off the ignition with the key (so as not to slam the HV coils).
11  If you do not plan to do the dynamic synchronisation afterwards DO NOT FORGET to tighten the carburetor vacuum screws!

ADJUST THE DYNAMIC SYNCHRONISATION

01
Unscrew the vacuum screws located under the 2 carburettors (for me Bing CV 40mm).
02
Connect the two Twinmax tubes to the inlets previously blocked by the two vacuum screws.
03
Switch on the Twinmax and set the needle offset to "0" using the two buttons on the housing (button 1: offset / button 2: sensitivity). The result of this step will determine all future settings. The needle must be centred at "0" (motor off) and the sensitivity of the instrument at max.
04
Start the motor (which must still be at its operating T°C) and reduce the sensitivity of the instrument to 3/4 of the maximum (sufficient for good adjustments).
05
With the idle speed set, normally the needle MUST NOT deviate to the right or left as you have just performed the idle timing!!!
06
At the stop of both carburettors, touch the throttle cables and find the one that is the tightest.
07
You will be assisted by a third person who will slightly accelerate for you up to 1500 rpm (that's enough!) just to tighten the 2 accelerator cables a little bit.
08
Using pliers, play on the tension of the tightest cable (loosen the tension a little) until the needle of the Twinmax is perfectly aligned with "0".
09
Congratulations, the dynamic synchronisation is finished and perfectly adjusted!
10  Switch off the ignition with the key (so as not to slam the HV coils).
11
DO NOT FORGET to tighten the carburettor vacuum screws!

    Article written by "Reiler" (thanks to him). Don't hesitate to visit the forum, it's a real gold mine http://www.flat-twin-bmw.com/