Balancing SU carburettors info

[simonhorton]

Hi All,
I'm thinking of buying a carb balancer that uses rubber pipes and adaptors that is used to balance side draught Webber and Dellorto carbs
- adaptors and pipes fit into inspection hole by butterfly's

Would it work the same if I used the breather connections on SU carbs by the butterfly's ?

Instead of buying a balancer that goes over the air intake of the carbs

Regards

[SprintMWU773V]

Would it work the same if I used the breather connections on SU carbs by the butterfly's ?

Given the carb draws air through the front part I can't see why attaching a pipe to a totally different an unrelated part will be of any use. Stick to the normal type. Personally I don't like the Gunson Carbalancers, they're a bit rubbish. There are better made and more accurate devices out there.

[mahony]

The last guy who tuned my sprint used one of these

http://www.ebay.co.uk/itm/CARB-BALANCER ... Swxp9W2xyb

[Jon Tilson]

Unless you are tone deaf you can set them absolutely fine with a length of narrow bore tube and your own ear.

The trick is to hold the tube end in the very bottom centre of the air inlet for each carb, with the tub end at a slight angle to the airflow.

You can hear the hiss distinctly and a few twiddles to put the carbs in and out of synch will soon teach you how to do it.
Synch them at about 1000 rpm and then drop the screws the same amount to your requirements.

Jonners

[Galileo]

I've got something similar (Morgan Carbtune) that I use on my bike, but each carb has it's own vacuum take off unlike the twin SU setups that only have one. I guess you could drill and put one in, bit desperate though!

[soe8m]

Unless you are tone deaf you can set them absolutely fine with a length of narrow bore tube and your own ear.

The trick is to hold the tube end in the very bottom centre of the air inlet for each carb, with the tub end at a slight angle to the airflow.

You can hear the hiss distinctly and a few twiddles to put the carbs in and out of synch will soon teach you how to do it.
Synch them at about 1000 rpm and then drop the screws the same amount to your requirements.

Jonners

No, you balance the carbs at the idle revs you want. Not balance at a higher revs and then turn down screws equally. In the idle region the slightest turn does make a whole lot of difference. Also when balanced at 1000 revs the angles can be different of both throttle valves. For example when a throttle valve is fully open half turn down has less effect when the throttle valve is almost closed and then half a turn less. You balance at idle revs you want.

The accuracy of the flow meter is very not important. Who cares the amount of air is 3,9 kilo or 4.3 kilo. As long all carbs are the same. Therefore you use one flowmeter for all carbs. There are sets available but these can differ slightly per flowmeter so it's still not balanced. Use one flowmeter for all carbs and then you are sure they are all the same.

Jeroen

[dursley92]

I use one of these on my SU's and it seems to work pretty well if you don't trust the listening method.

[Carledo]

I learned to balance twin carbs by ear in 1970 and have been doing it the same way ever since. Once, for a bet, I got a pair checked with a "proper tool" after I had balanced them. Easiest tenner I ever earned! The human mkI earhole is surprisingly efficient!

Steve

[Karlos]

My view is that on Dolomites with twin SU carbs and standard intake manifolds, you have to use a carb balancer, or listening tube, that measures the flow infront of the carb. You can't measure the flow after the carb because there is the manifold integral balancer pipe. If you measure after the carb (or after the butterfly) you are not measuring air passing through the carb, the reading is related to the manifold flow and is affected by the other carb.
Hopes that helps.
Karl.

[Toledo Man]

I bought THIS metal carb balancer from my local Moss.

[cleverusername]

You can use a dellorto webber carb balancer, I just stuck a piece of plumbing pipe on the front to fit it to the SU's. They were going cheap an ebay.