The Keihin CV40 is a great little carb. Very simple and easy to understand and work on.
I agree with all the folks above that have advised you to go back to stock. In the process, disassemble the carb completely and clean everything spanky clean with mineral spirits and carb spray. Replace any NON-STANDARD stuff you find in the carb. If you can fit a 1/8" drill bit in the hole in the slide, replace the slide (someone has drilled it on you). You will probably want the #46 low speed jet (but get a #45 too), and a #180, 185 and 190 high speed depending on your air cleaner and pipes. Doesn't cost you very much to get the extras so you can experiment without needing to run back to the store.
While you have the carb all apart, turn the body over and make sure that the air/idle mixture screw is accessible. If not, carefully drill out the plug and gently remove the needle screw. Spray the hole out generously with carb cleaner spray. Preliminary setting is 2 1/2 turn out. Adjust for best idle and then back out a 1/4 turn.
Also while you have the carb body upside down, remove the three screws from the accelerator pump and replace all of the guts of the accelerator pump with new stuff (especially the diaphragm!).
Put it all back together with new orings, seals and gaskets. Use the "U" tube method with some clear plastic tubing on the float drain to check the float level. If necessary, take the bowl back off to adjust, but be gentle. A little goes a long way!!
Fire it up and see how she responds. If too rich or lean, try the next/previous size jets. That simple!
TQ
