British Classic Motors - SU Carburetor Re-Bushing Service
NEWS: Our re-bushing service will also be available in the UK from June 2016 at VERY competitive prices - e-mail me for more information at
The SU carburetor relies on a good airtight seal between the throttle shaft, and the bushes cast into the carb body. If either the throttle shaft, and/or the bushes are worn excessively, it is not possible to obtain a smooth, even, idle. You will probably also find that you are unable to bring the idle speed down sufficiently.
The reason is this: with the throttle closed, the engine is still seeking air in order to run, and it will find it wherever it can; wear around the throttle shaft is a perfect place to find it. Once the throttle is open, the wear becomes far less of a problem, as it's easier for the engine to draw the air it needs through the carb venturi (choke) than anywhere else, once at idle again however, the problem returns.
The only way to renew these bushings is by line-reaming out the old cast-in bushes, and pressing in new Oilite Phosphor Bronze bushes. These bushes are manufactured to very tight tolerances, and contain 19% SAE30 oil, for extremely long life. Not only is it critical that the bushings are themselves in perfect alignment to prevent binding of the shaft, they must also be perpendicular to the venturi, to ensure the throttle discs close correctly.
It's important to note that, unlike many rebuilders, we do not ream the carburetor body all the way through to the bore; but, in line with the original SU factory recommendations, they are line-reamed only to the exact length of the new bushes. This significantly improves the sealing of the throttle shaft.
This shoulder can clearly be seen in the image below.
SU carb body line-reamed for new throttle shaft bushes
The charge for this service depends on whether or not we are doing your carburetor rebuild. If we are, the charge is $65.00 per body, or if you are doing the rebuild yourself, the charge is $85.00 per body, plus return Priority Mail postage at our actual cost.

For details on where, and how to mail the bodies, please refer to our Ordering Information page.

Can I help?

If you have any questions about this or any other of our services, or you simply have a question about your carburetors, please don't hesitate to e-mail me at; I will help in any way I can.
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British Classic Motors - More than 40 years of SU Carburetor Restoration and Rebuilding experience..............