[TR] Compression check: what does this mean?

[Randall]

Well, for sure you have something wrong on #3.  With those results, it's
hard to say for certain just what; but the problem should become apparent
when you get the head off.  If there isn't anything obviously wrong with the
head (like oil caked on the back on the intake valve for #3, showing that
the oil was going past the valve stem) or obviously wrong with the #3
cylinder wall; then pull the #3 piston out and see what you find.

My guess is either broken ring, or scored cylinder wall.

However, 120 psi of compression should still let the engine run reasonably
well.  My guess is that the poor performance is mostly from the fouled plug.
So if you want to wait until after the driving season, just change the plug
(maybe to one step hotter to help avoid fouling again) and go on.

-- Randall