Twinmax Vacuum Balancing tool, with carrying case

The Twinmax is a carburettor/throttle-body vacuum synchronisation tool, essential for ensuring the smooth-running of any engine. It shows the vacuum differential between two points of measurement, enabling fast and easy throttle-intake balancing.

The current product (available from 2023 onwards) has a black fascia. The photos showing the silver fascia are for illustration of the kit contents.

Parts List - what is included in the kit

Twinmax Carburettor Balancer x 1
Battery PP3 x 1
Vacuum tubes 6mm diameter x 0.85cm x 2
Chromed Brass threaded adapters 5mm + o-ring x 2
Chromed Brass threaded adapters 6mm + o-ring x 2
Tough ABS plastic carrying case

Note that the kit does NOT include the 4mm adapters for BMW motorcycles. These are available here.

Features

The Twinmax can be used with almost any engine/any number of cylinders and is suitable for synchronising modern fuel injection intakes as well as traditional carburettor-based engines.
This is a precision electronic tool and so contains no mercury, nor has any moving parts used for the pressure measurement (such as springs, weights or dials), ensuring it is compact, portable and can be used in any orientation or position. There is no need to keep it vertical like traditional liquid or weight-based tools so it can be used on the road for real-world checks.
It has an accuracy equivalent to 1mm of mercury.

Why use the Twinmax vacuum balancing tool?

Balancing the vacuum intake between cylinders is critically important to ensure the smooth running of the engine and so reduce stress on the crankshaft and bearings.

In any engine there are multiple mechanical components that form part of the control system of the air/fuel intake.
Over time and usage, these components can wear, stretch and loosen etc. outside their normal tolerances resulting in the butterfly valves not operating 100% in synchronisation and so allowing slightly different air/fuel mixtures into the cylinders combustion chambers.
The difference between these fuel mixtures in the cylinders will cause rough running, reduced engine response, inefficient power delivery, vibrations and increased stress (wear) on the crankshaft and bearings.
The use of a balancing tool such as the Twinmax as part of regular maintenance procedures can have an enormous beneficial effect on the lifetime of an engine.

Advantages of the Twinmax over other balancing tools

Other tools use various methods such as analogue dial gauges, mercury-filled tubes or spring-balanced weights to show the pressure in each cylinder. As they are mechanical devices there is always the potential for errors to due to the internal moving parts.
It can be difficult to guarantee that each gauge or tube will show exactly the same reading for a given amount of vacuum pressure, due to differences in manufacturing tolerances, differences in friction, differences in mercury volumes or the tension of internal springs.

As the Twinmax shows directly the vacuum difference between the cylinders using a single electronic pressure sensor there is no mechanical error possible and no need for any absolute measurements or comparisons at all.
The Twinmax only shows the pressure difference, which is exactly what you are interested in: you need to achieve zero difference.

Other disadvantages of mechanical tools are that they are more delicate and susceptible to damage from rough-handling/being dropped and often are bulky and have to be used in a vertical orientation.
As the Twinmax is so compact and has no mechanical measurement components it can even be fixed to the bike and used on the road to show how the intake control is functioning under real-world conditions/loading.

How to use the Twinmax

Note these are generic instructions. Always consult the service manual for your vehicle to ensure you follow the manufacturers recommended procedure.

1. Run the engine until it has reached its normal operating temperature.
2. Switch off the engine.
3. Connect the two Twinmax tubes to the vacuum points on the two cylinders to be compared.
   (If there are more than two cylinders, use the one with the lowest vacuum pressure as the reference.)
   
   Vacuum test points can take various forms.
   - a spigot closed off with a rubber of plastic cap. Simply remove the cap and connect the Twinmax tube.
   - There may be a “balance pipe” between the cylinders. Disconnect this and connect the Twinmax to those spigots on the throttle bodies.
   - A screw in the intake manifold. Remove this and use the corresponding (M5/M6) Twinmax adapter.
   - If there are no vacuum points it may be necessary to drill and tap the intake manifolds to be able to install the Twinmax adapters.
   
4. Calibrate the Twinmax (engine off)
   Press the red button on the Twinmax to switch it on.
   Set the SENSITIVITY knob to MAX.
   Adjust the ZERO knob until the needle of the meter is at 0 on the centre of the scale.
   Set the SENSITIVITY knob to MIN.
5. Balancing the intake
   Start the engine and allow it to idle.
   If there is little deviation of the needle from zero, slowly increase the SENSITIVITY until a deviation is shown.
   Make the adjustments as per the service manual to correct the deviation. This may be a screw on the throttle/carburettor bodies or it may require the adjustment of the play in the throttle cables.
   Increase the SENSITIVITY to show greater deviation if the adjustment procedure allows a corresponding fine-adjustment.
   Check the deviation at various RPM values.
   
   It is recommended to perform this procedure every 5-10.000km.

Example of using the Twinmax by Jim Von Baden on a BMW R1200.

PLEASE NOTE: This is a generic product which is displayed by default for all bike models. However, please check carefully the product description to confirm compatibility with your bike.