This modification is intended to limit the fuel squirted from carburetor accelerator pump into the engine for an increase in performance and fuel efficiency. There is a metal tab where this modification is done, making it look like a adjustment screw was designed to be located here. With my carburetor, the squirt previously continued for about 2.3 seconds when I hammered the throttle open, and now with the mod it is about 1 second. If you use a drill to drive the tap, be aware that you need to back it in and out while advancing a little each time--otherwise the tap could get jammed in the hole. I used a 6-32 tap and drill set because I already had one, and a 6-32 x 5/8" stainless machine screw from my local hardware store. I forgot about the plastic cover and trimmed the length of the screw down--it was almost too short. The original 5/8" length of the screw would have been just right. I snipped a piece of spring from a ball point pen to use, and squirted a little locktite on the screw to hold it in place. The black plastic cover needed to be notched, and I used a round file and an exacto knive to do it (the cover has a flat surface ready for just such a cut-out).
Hardest part of this? Removing and re-installing the carburetor by far. Measuring the fuel squirt time is a little tough to coordinate, with one hand on the throttle, the other holding up the carb with the rag over the barrel (it squirts a fair amount of fuel) and holding the stop watch. The mod itself only takes a few minutes.
Copyright 2003 Rob Crockett, all rights reserved.