I got the manual on line last night, should have done that before I
posted the question.
turns out normal range is between 80 and 50psi. Maybe the rings and
valves are Ok.
The air filter was a mess, looks as if it hadn't been changed or
looked at for a long time. It was covered with moths, leaves and other
muck. Maybe it wasn't getting enough air? Maybe I'll rebuild the carb,
if it's anything like the filters it'll need it.