IN a 2-Stroke engine
the atomized mixture from the carburettor is sucked into the
Crankcase on the up-stroke of the piston and forced
via the transfer ports into the cylinder on the down-stroke.
This process can be seen at the website http://www.keveney.com/twostroke.html.
In the 1970's, a popular tuning technique
was to stuff
the gaps inside the crankcase housing with Epoxy Resin to
increase the Crankcase Compression Ratio in
an effort to get more mixture into the cylinder and
hopefully get more power.
On a Piston-Ported
engine such as the VeloSoleX S
3800 engine without
a Reed or
Rotary Crankshaft Valve, the ideal Crankcase Compression Ratio is around
1.45 : 1. Any value higher than this and the mixture tends to
get forced back out of the carburettor particularly
at low RPM and also if the Carburettor Venturi Diameter
has been enlargened.
Since the VeloSoleX S
has a Crankcase Compression Ratio of 1.45
: 1, it is NOT RECOMMENDED
to improve this value further.