On Tue, 27 Mar 2012 03:36:21 +0000, notbob wrote:
Sounds like you want to know if there is enough compression in yer
2-stroke. When I was a motorcycle mechanic, lo these many yrs ago, the
rule of thumb for both 2 and 4 strokes was: Pull the spark plug. Put yer
thumb firmly over the plug hole, make sure the throttle is wide open,
and cycle the engine. If there is enough compression to blow air past
yer thumb, that's good enough. If not, you need a rebuild. Typically a
bore job and new rings.

I've been told that one too in the past (and used it - it is a good
test). I did have a 10HP engine which passed the 'thumb test' though but
still didn't have enough compression to run; that one turned out to have
major damage toward the bottom of the bore, with minor piston damage too
(but rings were intact).

The long-term correct fix was a rebore, but the emergency redneck fix
(more to see if it would even work than anything) was to patch the damage
with epoxy*. Two years later it's still running like that... :-)

* can't remember what I used now, but something rated for high temp and
oil contact.

cheers

Jules