this is from my book "how to build and power tune Weber and Dellorto"


just highlighted this yesterday.

"A too small accelerator pump jet will cause the engine to die momentarily when the accelerator is depressed. Too large an accelerator pump jet causes the engine to 'bog', which effectively amounts to the same thing, (a slow car) and then pick up after the excess mixture has been removed from the engine"

"the following gives gives a basic starting range of accelerator pump jet sizes for modified engines (Ie with long duration camshafts, worked cylinder heads, high compression, extractor exhaust systems). Try the smallest jets first. The accelerator pump jets are listed as average, so expect to come down for sized for engines that are not overly modified."

Weber range for average use is 30, 35, 40, 45, 50, 55, and 60

500cc per cylinders (m10 ballpark): 45 on the high side, and 40's on the low side


that might head you in the right direction.

it gets more complicated with needles and stuff, but that's the basic guideline
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needy and demanding 72 02