Chicagoland MG Club
SU Throttle Shaft Tip
Have you replaced a throttle shaft on your favorite British sports car lately and wondered how you were going to pin the idle adjustment lever and the throttle stop lever to the throttle shaft? Or better yet, how do you drill the hole for the mounting pin, and keep the Concours look, by not having to drill a second hole in the lever?
The whole idea is to try and reuse the original hole in the lever that gets pinned to the shaft, and have the lever positioned properly so that you don't run out of adjustment for the throttle stop or the idle speed screws. This helps to keep the rebuild of the carburetor looking as original as possible, which is necessary if you're going all out for the points judging. To properly align the idle levers, you first need to install and center the butterfly valve in the carburetor using a new shaft.
Once the valve is installed, and centered so that it closes fully and does not bind, you can slide the lever onto the shaft. Adjust the idle speed screw or the throttle stop screw, (depending on which carb you're working on) so that there is about 1/16th of an inch or so protruding through the lever. This assures that you will have some adjustment in case something slips a little. By holding the butterfly valve completely closed with one finger position the lever so that the adjustment screw is against the flat on the carb body that it normally rests on. Now the "shop trick". Put a drop of cyanoacrylate ester (Krazy Glue, or Loctite Super Bonder) on the shaft to glue the lever to the shaft.
Once the glue has set up you will be able to adjust the screw on the lever so that the retaining pin hole is perpendicular to the base of the carburetor. This will allow you to drill the new hole in the shaft, with a drill press, using the original hole in the lever as a guide. All that remains after this is to press in the retaining pin, and complete the rebuild of the carb.
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