Valve seals just keep oil from getting down beyond the guides. What you
probably have is bad valve or valve seat.
Use your data to compare one to another. Numbers don't mean too much except
as one cylinder relates to another. Pull the head, check the cylinder walls
for the ridge that occurs at the top. The ridge will give you an idea of
cylinder wear. If the ridge is slight or nonexistant, then just get the
head serviced and you are good to go. If the ridge is more than the
thickness of a fingernail, then think about re-bore with new pistons. You
probably only need a valve job and some hardened exhaust valve seats
installed. Your analysis points to good rings/cylinders.
Did you pull the valve cover off and make sure there was valve clearance
(lash) when doing the tests? You really don't have to struggle to find each
cylinder's TDC, just turn the thing and stop after the intake vavle closes.
Test with both vavles closed. You might get a better idea of cylinder wear
if you test somewhere below TDC as the top ring would seal a little better
at the very top of the cylinder, against the ridge.
Using a quart every 100 miles means either your exhaust fumes are blue or
there is an oil leak somewhere. Check out the rear engine plate for signs
of cracks or leaks.
Those little motors are pretty tough. Take the head off and see what's
there.
Cheers,
Derf
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