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Re: Trac Engine  MacDo-@aol.com
 Jul 19, 2001 19:46 PDT 
Sean, you mentioned in an earlier message that you "had good spark." If that
is true, then putting a little fuel in the combustion chamber through the
spark plug hole should give you a few seconds of running almost without fail
as long as the piston is moving and providing enough compression.
So, lets try to sort this out.
Did you check the compression? Or, with the spark plug out and cranking the
engine with the starter motor, can you put your thumb over the plug hole and
feel any compression? Does it feel strong, i.e., pushing your thumb away and
leaking past, or can you contain the pressure easily. An engine with only
300 miles on it should have 130 psi pressure and you would not be able to
hold all that with your thumb. If the compression is weak, say 60 psi or
less and you can hold the pressure with your thumb, it will be almost
impossible to get the engine to fire no matter what you do. This sounds like
where you are. The rings may have become gummed or carboned up and
compressed and stuck into the ring groves on the piston. This would result
in very low compression and the engine will not run.
Been there with this one on a Honda Spree. The moped had 2900 miles,
compression of 35 psi on my tester, good strong spark, and would not fire
even with starter fluid. Another Spree with 3400 miles had compression of
120 psi and runs very well. I think the previous owner tried motor oil in
the tank because the rings and piston were carboned so badly they needed to
be replaced with a used piston and rings. The compression is up to 130 psi
and it runs great.
So, I ask again, what is the compression???
Before you dissemble the engine, you may want to try some carb cleaner to
free the rings. Remove the spark plug, turn the engine by hand until the
piston is near the top, add a liberal amount of carb cleaner and let it set
overnight, recheck the compression. If the compression is 80 psi or more,
the engine should run.
Put the wiring back the way it was when you had good spark. The ignition for
a moped does not run off the battery!!! The battery is for the starter and
turn signals when the engine is at idle and the magneto is not putting out
enough voltage to run all the lights.
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