From:Steve Marks
E-Mail:<steve@microdesign.ltd.uk>
Subject:RE: RE: RE: RE: KL/KJ/Deluxe cylinder comparison
Response to:657
Date:Tue May 18 05:10:37 2004
The domed piston would decrease the clearance, therby
increasing the CR. In two stroke tuning, the curved contour
of the piston crown is exactly reproduced in the cylinder
head to produce a 'squish band'- an annular ring around the
outside of the bore. The centre part of the head would then
be opened out to produce a combustion chamber the volume of
which is determined by the required compression ratio (CR).
Squish band  clearance (gap between piston crown and head
when piston is at tdc) is usually set to around 40-50 thou.
Too little and there is a chance that, at high rpm, the
piston could hit the head as a result of engine components
flexing and/or stretching. Too much and there is likely to
be trapped mixture left in the squish band area which would
result in poor combustion and loss of power. The squish band
is designed to shoot the mixture up into the combustion
chamber towards the spark plug - the KL picture shows a
similar annular band around part of the bore but with a
'gap' routing the mixture across to the valve/spark plug
area. It's interesting to see that these 'squish band' ideas
were around so long ago - it would be interesting to know
what the clearance was and what the actual CRs were. I guess
the location of the valves on the side of the bore means
that the CRs would be a bit lower than a modern day two
stroke....
Another good thread - thanks to everyone for keeping the
brain cells going.

----- ORIGINAL MESSAGE FOLLOWS -----
Thanks to Marty and Perry for this technical stuff.

Its interesting that the KL has a domed piston - I would
have thought that this would increase the clearance to the
roof of the combustion chamber ??  Does the KL have higher
compression ?

----- ORIGINAL MESSAGE FOLLOWS -----
  Marty sent me comparison photos of KJ and KL pistons.
I added them to the bottom of the cylinder page referenced
below.  Enjoy.  Thanks Marty! ... Perry

----- ORIGINAL MESSAGE FOLLOWS -----
  OK folks.  I've taken the photos and comments provided
by Marty and made up a web page showing the differences
between cylinders.  You can find it at:
http://www.hendersonkj.com/ffo/cylinders/cylinders.html