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[tieclubbyestate]

as above

[irish.yobbo]

A tachometer is useful, but not especially important when tuning a carby. If your idle speed is out, no big problem provided that your mixture is right.

First, start the car up and get it to running temperature. If it's a new carb that hasn't been tuned at all, turn the mixture nut (underneith the carby, attached to the jet) in all the way, and then turn it back out by about 2 1/2 turns. That should get you started.

Using the idle screw (which is next to the dashpot), twist it in or out until it 'sounds right.' If you're tuning a car with one on already, it should be about right. If it's a new carby that's never been tuned, you may need to raise the revs on this to get the car stated in the previous step

The next thing to do is to adjust the mixture, which is the nut under the carby again. Turn it 'in' to lean the mixture, 'out' to enrich it. On the side of the carb body there is a pin, lift that pin up about 3/4's of its travel. If the engine speed increases and stays high then the mixture is too rich. If the revs fall and the engine sounds like its going to stall then its too lean. The revs should rise and then fall back to about original. Then the mixture is ok. Play around with the nut until you get it right.

Once you've done this, the carby should be tuned. You may need to adjust the idle screw again, as the mixture can sometimes change the idle speed.

Note that this will give you a perfect tune only if you have the right needle. To check this, you will really need to see a specialist. But this will get you started and running.

Edited by irish.yobbo, 09 April 2011 - 04:35 AM.