As I knew would happen, I'm slowly replacing everything on my 77B engine.
I've rebuilt the carb, new choke, water pump, timing chain, tensioner, and
all the assorted tune-up goodies, but there is still a problem. When I get
to about 40 mph in high gear, a strange vibration starts. If I push in the
clutch it goes away, and comes back when I release the clutch. If I rev the
engine with the clutch in (while going 40mph) I can get it to stop, and the
engine will run past 40 without the vibration. If the problem were in the
drivetrain or suspension, I would assume the vibration would remain, even
with the clutch depressed. Also on a 100 mile trip, it went through a quart
of oil, but don't ask me where it went. This doesn't happen all the time,
and below 2000 rpm it runs great. Could this be bad main bearings? (The
engine has 92,000 miles on it) If this is the case, winter in Montana is
not a bad time to have the engine out.
Thanks in advance for any ideas.