CD Stromberg

The carby depicted below shows both early and late model versions, so some parts will vary between models. The late model does not have an adjustable jet but rather an adjustable needle.  Apart from that, the early and late model carbs are very similar. In the late model a special tool is required to adjust the mixtures. It goes down the piston tube (6) and is used to adjust the height of the needle. In the earlier models the needle is fixed in the piston and the jet (1) is adjusted to control the mixture at idle.

When setting the float height do not bend the tag excessively. The tag needs to be at a tangent to the needle for correct operation. Try instead to use different thickness of washer under the needle & seat. There are 2 sizes in the kit. I always start with the thickest one.

Do not handle piston assembly or suction chamber roughly as they are precision made. Some models may have an air valve lift pin which is used to check mixture. Raise air valve slightly, if engine RPM increases then the mixture is too rich, if the engine stops it is too lean. The engine should remain the same or just drop slightly on lifting the air valve when the mixture is set correctly.

The photo below shows a common problem which has developed over the years. Some screws will eventually break due to fatigue caused by over tightening the screws. All you can do is drill & extract if your lucky, re-tap the thread if salvageable or retap to a metric size slightly larger. Don't risk it and leave one out. If the diaphram does not seal correctly the carburettor won't perform properly.

The float pin retainer can spread due to careless installation of the float. The pin should be retained tight & not move. It is easy enough to retension it. Using pointy nose pliers, squeeze the ends together lightly then move one leg aside so they can pass each other. Don't over sqeeze them otherwise there will be no gap to push the float pin through.