Hello all,

has anyone suffered with this problem or do you know what is causing it:

when turning the propeller by hand it sometimes does not turn the engine over with every prop turn. The rubber donut coupling between the gearbox and the engine can be seen not turning when this happens. Seems like there is a gearbox problem - have taken it off and opened it up but nothing obvious wrong there. Maybe the taper bearing on the propeller drive shaft in the gearbox is worn/loose and the big nut that holds the big crown wheel on the shaft also needs a re-torque. Or is there some other problem that anyone knows of?

Many thanks
  • Re: C Type Gearbox problem

    by » 12 years ago


    Sounds like you are on the right track. If the doughnut is not turning and the prop is, It could be the tapered bearing and sleeve on the propshaft. If it were the doughnut or the splined shaft in the doughnut, you would have seen that right away. If you have the right tools and expertise, you can disassemble prop shaft. you need a special jig to mount the prop flange in and a BIG torque wrench. Definitely not an easy job and the gearbox case is easily damaged if not done properly. Just retorqueing is not enough. The tapered sleeve and bearing need to be examined for wear if they are slipping.

    If the propshaft is slipping, your best bet is a Rotax mechanic with the proper tools.


  • Re: C Type Gearbox problem

    by » 12 years ago


    thanks for the information and advice. I don't have the tools and the understanding to do the job so I'll send it off to a Rotax mechanic and get it looked at.



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