High-Performance Weber Upgrade Part 2

The Weber 48mm IDA has approximately 100 parts to each side, so it is a good idea to make note of where you keep them. Since most of the parts are small and easily lost, dedicate a section on your workbench for this project and don't move things until you're done. If you're doing this for the first time, it may be a good idea to take apart and put together one carb at a time, leaving the other as an example.

Once the velocity stacks, the filter screen and fuel filter have been removed from the carb top, remove the eight screws holding the top to the main body. Below that, remove the gasket to expose the inner workings of the carburetor. Shown here is the float bowl in the middle; nearest is the main jet stacks on either side and the idling jet stacks on the outsides. To the right of the float is the accelerator pump, and facing into each auxiliary venturi (called boosters) are the pump jets.

All of this must be removed, but you'll only be keeping the boosters, the gasket and the pump jets. Everything else can be set aside. The needle valve will be replaced with a 3.5mm unit (instead of 2.0).

Don't forget to unscrew the inlet and exhaust discharge valve at the base of the float bowl.

Remove the mixture adjustment screw and plug from both throats.

At the base of each side of the carburetor is a bolt that holds the throttle lever to the throttle shaft (arrow). Behind the lever is a retainer, spring, dust seal and ball bearing pack. Remove these on both sides. Once those are removed, unscrew the four retaining screws on the face of the butterfly. They simply slide out from the throttle shaft and can be discarded.

Wiggle the spring out from under the accelerator cam, and tap the pin out from the accelerator lever (arrow). Once the pin is free (don't lose it), slide the shaft out from the body and set it aside.