I guess I should mention that my "tooth wheel" is a little persnickity. It is best adjusted by turning the ecentric screw (axle I have been calling it) untill the wheel teeth do not make contact with the drive worm (screw threads on the drive tire shaft) then snug up the lock nut so you can just turn the screw.... And slowly turn the screw untill the tooth wheel just makes contact. Spin the tire (a lot.....one complete revolution of the heart shaped cam) and see if there is any binding, my wheel does not seem to be perfectly round (or the teeth are deformed) and it has a few tight spots as it turns...... It is important to get this "gear mesh" just right......Ie you can not just run the axle screw in tight and call it good. In fact the axle screw only threads into the lock nut on the back..... Turning it only adjusts the tooth wheel closer to or farther from the worm gear. Get a strong light on the subject and look at what moves and how when you adjust that screw and I think you can solve your problem.
If we don't get it by the time I get home, I am considering doing a video on the adjustment.
We will solve this, it is just to neat a machine to be spoiled by this
