My problem with the old Genie SP99 garage door opener is when operating the unit, the large plastic spocket with chain sprocket atop both mounted on same shaft rises up away from the top of the opener and the stop "flags" on the chain miss the limit switched. The shaft/plastic gear/sprocket all rises up about 1/2" while turning and then the chain mounted "Stop Flags" do not contact the limit switches and therefore the unit does not stop of course. What is suppose to keep this drive shaft with plastic gear and chain sprocket from floating up.

Thanks
Dennis

Probably a thrust washer or bearing on the other end of the motor shaft.

Try to look at a later model to see what they did to correct the problem and do it yourself.

Thanks much