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Old 08-17-2010, 12:12 AM
mr.WFO mr.WFO is offline
Motorized Bicycle Newbie
Join Date: Aug 2010
Location: Texas
Posts: 17
Default Re: waiting on my engine

bairdco, awesome writeup on the reversed jug.

i was wondering if anyone has blueprint specs for these motors.

& reading thru 2 stroke performance tuning by graham bell i found this:

In an effort to minimise cylinder and piston distortion, some manufacturers have
chosen to use an offset squish type combustion chamber (FIGURE 2.2). The exhaust
side of a two-stroke cylinder and piston is always the hottest, even though cooling air
flow is much better here than on the back (inlet side) of the engine. There are several
reasons for this, all associated with the passage of very hot (630C) exhaust gas
through the exhaust port. The escaping gas heats the exhaust port and cylinder wall as
well as the side of the piston. This can cause the piston to expand abnormally and in
some circumstances to seize. To take care of this possibility, the manufacturer may
choose to increase piston to cylinder clearance, but this may not be desirable as extra
clearance can increase leakage past the rings and usually results in high piston wear. A
safer step is to move the combustion chamber to the rear of the head. If this is done,
the front of the piston crown is shielded from the combustion flame by the squish
surface. Then, when the front of the piston is heated during the exhaust stroke, it will
not expand so far due to its being initially much cooler.

did you snap a pic of the inside of the head? i'm getting curious to what a blueprinted/tuned happy time will put out.
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