Idle Screw reaction

[jhirasak]

Paul,

First, do you have a Air Fuel Ratio meter that you can use to record how your AFR varies as you drive? If not, I would highly recommend that you purchase one and use it to assist in your Weber tuning process. Without knowing if your AFR is too rich or too lean in your problem areas, it is difficult to provide you with accurate recommendations to correct the problem.

With respect to your idle mixture and idle speed questions, it appears that the idle fuel jet that you are currently using is causing a slightly rich condition based on your mixture screw setting of 1/2 turn out. Normally with your throttle plates fully closed, the transition ports should not be providing any air to control your idle speed. The air at idle should be provided by the idle jet holder and the air normally leaking past the throttle plate.

With respect to the transition problem near 2500 RPMs, it is likely due to your choice of emulsion tube or fuel level in the bowls if you can ease through that speed range. Without data on your AFR readings (too rich or too lean), and information on your current tube number, I cannot recommend which tube could improve your situation. Please post information on all of the jets that your are currently running.

Cheers,

John