Linkert BombSite VS Standard Venturi

1. The Venturi set screw and venturi set screw with ‘cone (without the spring). Either of these are used in the M53A if it is using the ‘single’ or regular venturi. It Is used in the M53A1 that doesn’t use the ‘bombsite’ venturi.

2. The Venturi set ‘coned’ screw with spring. This ‘coned’ venturi set screw is required with the spring in all MR3, MR4, MR4A, M53 and M53A that have a dual or ‘bombsite’ venturi. This venturi set screw with spring must be removed before removing the venturi.

3. The Venturi ‘coned’ set screw with spring. Note that the spring goes to start of the threads on the set screw. If the spring doesn’t it can ‘jam’ in the hole and damage the bombsite venturi.

NOTE: That because the M53 series uses the same main fuel nozzle, and that this main nozzle also uses a gasket, when a ‘bombsite’ venturi is used there is very little contact between the main nozzle and the ‘bombsite’ venturi making the ‘coned’ set screw with the spring necessary. This is also true of the MR series racing carburetors that use the ‘bombsite’ venturi.

NOTE: I have seen two types of coned set screws, ones with a slight 'cone' and ones with just a straight 'non-coned' portion to hold the spring.