The enlarged venture will cause the engine
to not suck as hard at lower rpms, so the
engine will be more sensitive to fuel level
being lower when the nose is up. It should
be easy to get a stock venturi to replace
your enlarged one. A smaller propeller will
also get the rpms up where the large venturi
wants them.

You should try to get a new "old stock" piston/
cylinder set at a flea market. They are much
better than the later production ones. There
is a flea market coming up in Westminister
on Feb 13, where you might find one. The
chances are much better on finding good old
parts at the Lebanon flea market in March.

The sub piston induction allows fresh air
to enter under the piston at TDC. This assures
that no vacuum remains from the engine
sucking through the carb during the upstroke.
This in turn allows the maximum transfer
when the piston reaches bottom.

The shims raise the cylinder so there is no
gap under the piston at TDC. It is important
with a muffler because it would let in exhaust
with very little oxygen instead of fresh air.

Since the cylinder is raised, there is more
combustion chamber volume, and thus lower
compression. To compensate, shaved heads
are used to get back the normal compression.

There is still power loss with the muffler, but it
is less than using a muffler without the shims
and shaved head.

Jenny

ps. I think the old stock in blister packs is the
best. They probably have an address as
Corona California. After cox moved they still
made good stuff for a while. I think the new
address was Warner California.

The newer parts came in plastic bags with
red, white design and black printing. Some
are good and some not so good. I can't remember
how to tell the lower quality ones, except that
the dual slit cylinders are all the crummy ones.

It might be that the cylinders that are wide all the
way from the base to the fins are the crummy ones,
and the ones that have a narrow neck are the good ones.