When the piston is sitting where it wants to be for the engine load
condition the mixture is correct. When it's forced low the mixture will be
rich. When
forced high the mixture will be lean. On acceleration you need to run a
richer mixture for a short time. If the piston is allowed to move freely the
mixture will remain correct for constant speed running but it will be too lean
for acceleration. The dash pot oil damps the rise of the piston forcing it to
be
temporarily lower than the steady state level. This enrichens the mixture
for acceleration. The speed of rise and thus the amount of enrichening can be
varied with the weight of the dash pot oil. Too thin or missing and you go
lean and stumble. Too thick and you go too rich and have a boggy, soft
acceleration. Just right and you have a crisp acceleration. The factory oil is
about a
10w, the same as ATF. You want the thinnest oil that controls the stumbling.
Motorcycle fork oil comes in a number of weights and in convenient screw top
bottles. A medical syringe available at the feed and seed store with a short
piece of vacuum line is ideal for changing dash pot oil.
How's that?
keith
In a message dated 7/27/2008 8:42:12 AM Pacific Daylight Time,
9laser3@bright.net writes:
Keith,
For those of us that are still technically challenged, ... can you break
that down for us? (:-)
Paul
-----Original Message-----
Subject: Re: [Roadsters] Carb tuning
What he said.
keith
In a message dated 7/26/2008 11:56:52 P.M. Pacific Daylight Time,
sandhoff@csus.edu writes:
> when I punch the motor at low rpm's the motor gasps for air and
> several backfire pops occur
Sounds like there's no oil in the dashpots. Unscrew those little
black plastic caps on top of the domes. Lift the rods out, and drop
them back in. They shouldn't just drop down - they should 'squish'
thru a tiny pool of oil. Add 20W, a splash of engine oil (10w-30),
some Marvel Mystery Oil, or some ATF (any brand auto trans fluid).
Takes only a couple of tablespoons or so.
-- John
John F Sandhoff sandhoff@csus.edu Sacramento, CA
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