Mystery dynostart pulley problem solved - Peak District club run

Hi all,

those of you on the Peak District club run might remember that it was impossible to tighten up the pulleys on my dynostart and unfortunately this meant I finished the run riding in a Pinzgauer (thanks Matt!).

Thanks to everybody that offered advice, tools, experience, a spare dynostart at the lunch stop. It's amazing what you can find a pub carpark !

Back at home I took the fan off to find that the woodruff key had some cut marks on it and didn't sit properly in the slot on the dynostart shaft.  A new woodruff key has resulted in quite running and the fan nut now stays tightened up, and the engine is fine.

So I think the damaged woodruff key was somehow working like a cam that prevented the fan/pulleys/washers from clamping up when the nut was tightened. 

Thanks to the club and organisers for a great day out.


  • Any ideas as to why the woodruff key was chewed up? Not exactly a prat that gets dismantled very often.

  • Hi John,

    sorry, no idea. It's about the only thing I didn't take apart while I was 'refurbishing' it.

  • edited October 2019
    Hi Roger, glad you have got things sorted, and also happy that you enjoyed the Event   Regards Pete 
  • Sorry, did not mean to cast aspersions upon any one or any thing, the word "prat" in my comment above is either a spelling mistake by my fingers or an autocorrect on the part of the computer. The word should have been "part"!

  • Sometimes if there is rust, dirt, or tightness in the plain keyway, it forces the movement to take place in the curved side. Movement on the curved side just makes things worse by pushing the woodruff key further into contact with the rust/dirt/tightness.
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