Specifications

Simple Rules for low speed calibration
If the mixture screw is more than 2 1/2 turns out, then the idle jet is too lean (too small). When
the mixture screw is less than 1 1/2 turns, then the idle jet is too rich (too large). These assumptions
are based on the fact that the speed screw setting is not opened more than 1 1/2 turns. If the
speed screw has to be opened 2 or more turns then this is also an indication of a lean condition
usually requiring greater change. At times it may appear to be showing signs of richness or
flooding it is really a lean condition. See pictures and notes in the tech 2 article supplied in the
kit instructions, view and please understand the need to keep throttle plate as near to closed as
possible so as not to prematurely expose the transition holes. This is what causes the visible rich
condition, and confirms the need to increase the jet size. JET KITS are available if needed.
EXAMPLE: With the speed screw set at no more than two (2) turns in after contact with the stop
lever; and the best idle occurring with the mixture screw set at 3 turns from bottom, indicates the
need for a larger Idle jet. Achieving the best idle at under 2 turns indicates the need for a smaller
idle jet.
The secret to understanding the critical nature of the carburetor set up and the advantages of a
WEBER over the other carburetors is the idle circuit. Referred to as the low speed circuit by
Weber, this circuit is responsible for 80% of the driving operation. This is the reason that the
Weber should give a fuel economy improvement over most factory carbs along with significant
performance gains. In the worst case you should not see a significant fuel economy loss over
stock, while improving HP and drivability.
The Weber Carburetor is a sequentially timed device to the motor like the distributor. Time taken
in the setup will provide more fun later.