Note: Picture to be used for reference only. Carburetor models may vary.
Note: Please read all the WARNINGS below.
a) Use a small screwdriver or pliers to unhook the spring (33) from the accelerator pump lever (34). Disconnect the accelerator pump rod (3) from the ball sockets at each end. Remove the small cotter (split) pin (52) from the top of the accelerator pump. Remove the pump lever screw (35) to release the lever, then unhook the spring from the airhorn casting. If possible, try to keep the accelerator pump from rising too far up in the well, as the top spring cup can catch on the slot in the accelerator pump well, and lock up the pump.
b) Offer up the new spring, hooking the square end into the breather hole in the airhorn, and hang the circle part onto the lever mounting boss. Wipe a small amount of light oil or anti-seize grease on the shoulder of the pump lever mounting screw (35). This is all the more important if you are using new Genuine Stromberg parts as both screw and lever are stainless steel.
c) Now, insert the screw (35) into the center hole of the new accelerator pump lever (34), making sure the ball end of the lever is pointing to the front as in the diagram (towards the float bowl). Then slide the ring end of the lever over the end of the accelerator pump top rod (10), and align the screw thread so it enters the airhorn casting boss without cross- threading or misalignment. Tighten the screw – do NOT over-tighten – using a wide flat blade screwdriver to avoid marking the slot. Do not try to attach the spring at the same time. It just makes it harder to get the screw in straight and it will pull the accelerator pump too high in the well (see above).
d) Reconnect the accelerator pump rod (3) onto the ball sockets at each end. We find it easier to fix the top end first. Insert the new cotter pin (52) to secure the top of the accelerator pump to the lever. And now, you can flick the end of the spring over the lever arm to finish the job.
e) Expert Stromberg tuners use the accelerator pump lever to ‘time’ the point at which the accelerator pump hits the power valve pin, and therefore, when it starts to enrich the mixture at the top end. This is achieved by carefully bending the lever at the end where it attaches to the accelerator pump link rod (1). Bending the ball upwards, effectively lifts the accelerator pump starting position up so it hits the pin later and increases the pump charge (or ‘squirt’) into the carburetor if the throttle is cracked quickly. Bending the ball end down has the opposite effect (rather like switching the link rod from W to S on the throttle shaft bracket) The new Stromberg lever in this kit is made to the original Stromberg blueprint specification, but please remember that it is a casting and cannot be warranted against constant adjustment in this area.
You’re done! If you think we’ve missed anything or we could improve on this Genuine Stromberg ‘How To’, please let us know. Email – firstname.lastname@example.org