How to balance your carbs

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How to balance your carbs by AMCQ46 A simple "how to" balance the carburettors on the VTR1000F. 1st thing you need to do is fit a vacuum adapter to the front cylinder intake. There is one already fitted to the rear which is used to operate the fuel tap, but the front take-off point is blanked off with a 5mm Allen head screw. You will need to purchase a 5mm threaded brass adaptor if you want to permanently fit the adaptor, or you can use a plastic adapter which probably came with your balance gauge, but if you do this you will have to refit the blanking screw after you do the balancing. Brass screws from Carbtune http://www.carbtune.co.uk/carbaccs.html, but you get a pack of 4, when you only want 1! perhaps if you call them up they will sell you a single. I suggest you also get a length of vacuum hose from them at the same time. To fit the screw you have to get the tank off and the air box, hence it is a lot less hassle to fit the brass one and then you can do any future checks without disturbing the air box. If you are going to leave the adapter fitted then they recommend that you remove the o-ring, and use a thread lock sealant. Also don’t over tighten; brass is not a strong as steel. First photo shows the location of the front vacuum take off point.

Then you will need to fit hose to the front cylinder and put a T piece in the rear hose [as you will need to keep vacuum to the fuel tap to run the engine], the T piece can be bought at Halfords for £1.50, you will find them in the same section as the nuts, bolts and electrical connectors.

As you have the air box off to fit the adapter, and it is easier to get to the adjuster screw, the first time you balance the carbs it will be easier to do it with the air box off.

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You need to get the petrol tank back on to get the bike started, but you can’t fit it in the normal place or you can’t reach the adjuster screw. I fit the tank backwards with the hoses on the opposite sides.

At this point you need to fit your balance gauges, these come in many shapes and methods from individual clock gauges, oil manometers or in my case a ball bearing comparator. As it is only 2 cylinders this one is fool proof, it has no calibration errors and is unbreakable the lower ball has the vacuum from each cylinder acting on each side, the upper ball is only for reference showing where zero should be.

Get the engine warm and then lift the idle speed slightly to a point where your gauges are giving a stable reading. If there is any difference between the readings from each cylinder or in my case if the moving ball is to either side of the reference ball, then you adjust this screw. Which direction will depend on which cylinder is high and which is low. Your reading will change so you can work out if you are going the correct way or not.


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After each adjustment, blip the throttle slightly and let it settle to the fast idle. Now you have got your carbs balanced the first time, you will not need to take the air box off next time. The adjuster can be accessed [just] with the air box in place. And if you route the 2 open ends of the vac pipes [new one from the front and one from the t-piece in the rear] to a suitable position where you can access them with the tank on you can now periodically check the balance without removing the tank...........clearly if you need to make any adjustment the tank has to come off, but this makes the checking easy.

Last job is to blank off the open ends of the 2 vac pipes. I used the plain section of a long M5 Bolt, but I am told Golf tee's are a great alternative It is important that you don’t have air leaks here so don’t try and seal on the treaded section of a screw. I then tuck these pipes up with the thermostat housing between the V so they can’t be seen.


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