How to Drill the Vacuum Port in the Carb Slide
Why? For faster throttle response. By opening up the vacuum port, the slide can move faster.
1. Pull the top off one off one of the carbs, and then remove the spring.
Pay attention to how the rubber diaphram is in place. You will have to put it back into the small groove when you are finished. This is a pain the butt and could take some time. One side took me about 15 minutes to get the diaphram back into the groove, and the other side popped in with about 2 minutes of effort.
2. Pull the slide out. It lifts out quite easily. Dump out the needle and white plastic piece into your hand and set it aside.
3. Look at the bottom of the slide. The small hole is the vacuum port. Drill it out to 7/64" bit. I would recommend getting a brand new drill bit for this. You want it to be a nice clean hole. Remove any barbs and smooth out the hole after you drill with a drill bit one size bigger.
4. Make sure you clean off every single fragment of metal from the drilling! Then put it all back together. Try not to pull your hair out when you are putting be diaphram back in. Just be patient. The diaphram is just a tiny bit larger than the groove it needs to go back into on the top of the carb, and will require some finesse. After the diaphram is in place, put the needle, plastic piece, and spring back in. Carefully put the top back on, and don't disturb the diaphram that you just spent so much time on.
That's it! Do the other side and you are done.