A typical model
engine crankshaft acts as a rotating valve. It has a window
or port cut into it and it is timed with the travel of the
piston.
To determine which
direction a crankshaft is designed to turn compare yours to
the photos below. Aero engines are normally designed to run
counter clockwise when looking at the front of the engine.
But clockwise rotation crankshafts are available from some
manufacturers. Many times we receive calls from customers
that have acquired second hand engines and they are not sure
if they have the correct crankshaft.
Some times an engine
can start in reverse and run fine at an idle but as the throttle
is opened it will usually stop or backfire and run the proper
direction. On very high performance engines, like the marine
engines shown at the bottom of this page, the crankshaft timing
is very radical and the engine may start easily in the wrong
direction.
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