Yes, I've used one but it was a long time ago. Here's some directions copied from a website:

It is important on engines with more than two cylinders that you always balance all the cylinders against one which remains the reference or constant. Often there is one cylinder which is intended for this use-your manual will tell you this. It is suggested you use tube "A" for the reference cylinder. For good results, the engine should be near running temperature. On an air-cooled engine or a motorcycle it is advisable to sit a fan in front of the engine/bike to keep the exhaust pipes and motor cooled. On bikes, beware of exhaust pipes getting very hot and blistering nearby plastic fairings, etc. Keep an eye on engine temperature!

1. Ensure there is slack in the cable from the twistgrip or throttle pedal. If there is not a master idle screw, ensure all cable or rod adjusters have some free play-this makes sure that all carbs are sitting at idle, i.e., with their valves shut. Position the TWINMAX conveniently on the bike, such as on the saddle or on top of the frame and switch it on.

2. Connect the tubes to the carbs-one on the reference cylinder and the other on to one of the other carbs.

3. Turn the SENSITIVITY **** fully to MAXI.

4. Adjust the ZERO know until the meter needle is precisely through the middle of zero on the scale; this adjustment is very sensitive and very important.

5. Turn the SENSITIVITY **** back to MINI.

6. Start the engine and allow it to settle to a steady tickover. Don't be afraid of blipping the throttle-this makes certain the throttles are properly seated on their stops.

7. Slowly turn the SENSITIVITY **** until a deviation shows on the scale. The less out of balance the two cylinders being tested are, the more you will have to turn the SENSITIVITY **** to show an imbalance on the scale.

8. If there is present reference cylinder, quickly check each cylinder with one tube and choose the cylinder with the minimum deviation from zero on the scale as the reference cylinder.

9. Adjust the idle/slow running screw on the carb being adjusted (not the reference carb) until the meter shows an equal deviation on each size of zero. The meter is very sensitive, so care must be taken to use small increments of adjustment. Blip the throttle each time you make an adjustment to ensure the throttles are properly seated.

10. Repeat for all cylinders.

Once all the carbs are balanced at idle, they must next be balanced on throttle opening. As before, balance each carb against the reference cylinder.

Note that the balance must be checked as the throttle is opening and the engine is accelerating, NOT as the throttle is being closed and the revs are dropping. With some practice, you will be able to do this efficiently, and you will also be able to check the balance at a constant throttle opening.

You may find that a cylinder will balance fine on the opening up stage, but not on a constant opening; the skill lies in being able to interpret this and achieve a balance between one and the other.

11. Start with the SENSITIVITY **** about the middle of its' range. Run the engine and this time open the throttle gently and run the revs up to 3000 or 4000 rpm and make a note of any deviation on the scale; again, if it is not pronounced, increase the SENSITIVITY.

12. Now adjust the carb throttle actuator-this is either a cable or screw acting onto a plate or rod and may be hidden inside the carburetor top. Be careful to make only small adjustments. Note that if there are locking nuts on the adjusters, doing these up will affect the setting so double check the results and blip the throttle to settle things out.

13. Repeat for all the cylinders.

14. Adjust the slack in the cable from the twistgrip/pedal to manufacturer's specifications.

 

Greg already posted the instructions. They are a bit more accurate than a good murcury vacuum gauge but their real advantage is being able to hook it up and ride. Observing readings at different throttle openings under load and then at idle after a run. When used in conjunction with an EGS/A-FR meter, its actually better than on a dyno.

Trying to set you fuel screws (pilot) with it or any such device on the VTR is almost impossible, you need to be on a dyno with a EGS/A-FR meter. Plumb the vacuum lines and plug them so you can sync without having to completely pull the tank; just tip the front up to get to the sync screw on the left side adjacent the rear carb.