Re: problem of piston rising about 1/4 in at idle, even with all linkages
and idle screws loosened.
I looked carefully at my old front carb....especiallyaround the place where
the butterfly valve is held in. It seems a little wobbly...plenty of room for
air to get sucked in. However, if this were the case, the piston would not
rise becuase air would go in through the bushing gap. Hmmmm. Therefore the only
place that air can be going is through the butterfly valve. Randy
suggested that the vacuum bypass valve on the butterfly was broken. This is not
so! It must be becuase the front carb piston damping is non-existant
for the first 1/4 in of piston travel....so it's easy for the piston
to raise under even a slight need for air. I also checked the butterfly
when closed, and you can't see light between the butterfly and carb wall.
I don't know...my reasoning doesn't convince me! How can it be sucking in air
enough to raise the piston. The air has to be going somewhere!! i.e. through
the butterfly valve and into the manifold....but the butterfly fitting is fine!
Perhaps the spring on the vacuum bypass is weak?? i.e. opening at very low
vacuum therefore allowing air past when it shouldn't? I guess the answer
to this is to solder up the vac. bypass valves per Randys original suggestion
and see what happens.
Marcus
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