...I've got a S.T. 3000 that is literally shaking my
plane apart. The prop came in perfect balance....
an 18-8 Zinger. The spinner wasn't bad, but the
back plate was way off. Regardless....the plane
shakes beyond belief. I know rubber mounting
might help....but I'm not looking for a Band-aid.

The problem is, the motor is very much out of balance.

My question is....why can't the crank be balanced
100% with the rod, piston, pin and related parts all
there.? What's with this 1/2 of the weight of the big
end business ?
Why can't the 2-stroke crank/piston assy. simply be
BALANCED ???

Am I missing something ? What are the counter weights
for on the crank ? Is there an imbalance/firing pulse
thing ....that I'm not awhere of ?

Take a V-8 auto engine for example....the crank is
balanced so that it will not rotate in any position on
centers....it's balanced. The pistons, rods, pins, ect.
are all weighed and made the same. The flywheel and
front pulley are balanced. The end result is that the
engine is BALANCED.

Not rocket science. So...what is the difference between
any other engine on the Planet....and a single cylinder
2-stroke engine ???

Wouldn't one assume that a single 2-stroke would be
"simply in balance" also ???

I'm not trying to make conversation about this. I have
two other planes set for the S.T. 3000's, including a 1/3
Pitts, and a Bridi Killer Bee. If this engine is simply a
shaker....I'm gonna hafta' be spending some coin for
some Moki's, I guess. (something in the 1.80 size).

Any, and all serious experience with balance issues
are welcome. Please....no theories about the rotation
of the Earth, or the position of the stars, ect.
I'm gonna start grinding on something....

Thanks....Dave.