I agree with srharvey, pull the blower motor check for ease of rotation, lube the bearing and at the same time check the brushes for wear. They're easy to replace on the newer 123s but you have to dissassemble the motor to put them back in the earlier models.
I've repaired a '77 and an '83. If you're living right and have to replace the brushes, hope it's like the '83.
offers the brushes and a booklet on how to do the job.
Good Luck, Happy New Year All!