On Sun, 22 Aug 2010 17:18:49 -0700, SF Man wrote:

On Sun, 22 Aug 2010 01:29:48 GMT, notbob wrote:

Size of the cylinder has no bearing on amount of pressure.

That makes sense. I practically filled the thing with carb cleaner
today. I'm letting it all dry out before I try again.

If this last ditch effort doesn't work, plan B is to bring it to a shop
for an estimate.

Check that the gasket between the carb and engine is good, that the carb
is bolted on tightly, and that the crankcase cover[1] is bolted on
tightly and with a good seal. On most of these engines the carb's fuel
pump runs from crankcase pressure, so if there are any leaks in the
system all sorts of strange things can happen - after ruling out spark
and fuel line/filter, I'd try there next I think.

Also pull the flywheel; it might be that the flywheel key has sheared and
the timing's out a little - maybe not enough to stop it running (with a
loss of power, but that might not be noticable), but enough to make it
hard to start.

[1] taking the cover off for a moment just to see if the bore is damaged
might not be a bad idea, either.

(re. compression, I posted here about a 4-stroke mower engine earlier in
the year; that one turned out to be compression loss due to bore damage,
even though it felt like it had "enough" compression when I stuck my
thumb over the spark plug hole)

cheers

Jules