Sunchronisation d'une Triumph avec le depressiometre TwinMax

Triumph Bonneville

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Bertrand wrote a small tutorial on carburetor balancing of old English cars using the TwinMax carb' sync... Thanks to him !

Preparing to balance the carburetors of a Triumph Bonneville

We assume that your carburetors are in good condition, (needle, plug without abnormal wear, etc.), and that the float and richness settings are correct. The ignition has been correctly adjusted before.

In these conditions, for the synchronization adjustment itself, 2 parameters remain to be fine-tuned:

• The adjustment of the idle screws which, as its name indicates, allow to adjust the opening of the valve at idle, with the control cable released.

• The adjustment of the cable pulling (lifting of the bushels or opening of the butterflies) between 2000 and 3000 rpm for example.

Carburetor balancing at idle

The engine is stopped after it has been warmed up. Simply connect your TwinMax to the intake pipes:

• On Italian bikes (Guzzi, Laverda) there are holes on each intake pipe. You just have to buy the small fittings proposed with the Twinmax...or make some by drilling screws and soldering a small tube of the right diameter.

• On the Commando... easy! Disconnect the small pipe between the pipes and connect the Twinmax pipes instead. Even the diameter is right. One more reason to ride Norton!

• On the Bonneville and Trident, the noble solution is to fit small tubes to each intake pipe and plug them back in after use with a small rubber stopper. Important! The length of the 2 rubber tubes must remain the same, otherwise the adjustment is wrong! The vacuum taps must be at the same level on each inlet pipe.

  • Once the TwinMax is connected, it must be powered by pressing the red button.
  • With the engine still stopped, turn the "Sensitivity" knob all the way to "Maxi".
  • Set the dial pointer to zero with the "Zero" button.
  • Decrease the sensitivity a little.
  • Start the engine and let it idle.
  • Adjust the idle speed by adjusting the idle screws of both carburettors so that the Twinmax needle remains at zero.

Balancing the carburetors at normal speed

Once your idle screws are correctly set, you need to adjust the balanced cable pull.

  • Bring the rpm to 3000 and lock the throttle.
  • By acting on only one of the two carburettors, adjust the throttle cable after having loosened its lock nut, so that the needle of the twinMax remains at zero.
  • Tighten the lock nut (be careful, it can make the setting vary a little)
  • Release the throttle
  • That's it! And sufficient most of the time.
  • Drive on!

Triumph Bonneville carburetor balancing tips

You can start again with the TwinMax set to its maximum sensitivity, but this may not be possible as our old carburettors can be a bit unstable, especially at idle. It works well like that... But I know you will try!

Think that the engine heats up, it doesn't like it and if it is too hot, the idle will not be good at its normal temperature.

With a little practice, it only takes a few minutes.

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