I have one worry after yesterday's fairly difficult but successful drive belt change on my Big Boy scooter. The main nut on the fron pulley now goes on much less further than before it came off. I read about a trick using a one inch paper card before putting the variator pulley front plate on, and skipped that. I wonder if that could be the cause? I just put the belt on the main axle and then put the front cover one. Here is what the difference looks like.


Pulley with nut tightened quite far on before removal and replacement.


Pulley with nut tightened not very far at all after replacement.

  • Are the vice grips aren't hitting the case and preventing the pulley from going on? Is the shaft splined and was there an index mark? That is one spline or tooth different than the others.
    – mikes
    Commented Jan 20, 2013 at 11:25
  • I'm not using the vice grips putting the pulley on! I'm using them to lock the pulley so I can loosen the nut and get it off. I realise I had the vice grips in the after picture, but I was busy taking the pulley off again when I took the pic.
    – ProfK
    Commented Jan 20, 2013 at 14:36
  • So now that that is clear is the shaft splined and is it indexed?
    – mikes
    Commented Jan 20, 2013 at 22:04
  • What do you mean by the shaft being indexed?
    – ProfK
    Commented Jan 21, 2013 at 2:58
  • 3
    Are there splines (teeth) cut in the shaft? If there are are they all the same or is one different from the rest. If one is different it must line up with the corresponding tooth on the pulley.
    – mikes
    Commented Jan 21, 2013 at 3:03

1 Answer 1


As was noted in the comments, the problem is probably that there is a key in the splines and the pulley which needs to be aligned in order for it completely fit onto the shaft.

While this is not your piece, it will show you exactly what I'm talking about. The splined area has a keyed area which is visible:

enter image description here

The crankshaft will have one which is opposite (one will protrude as a large spline, the other will be a larger groove for that spline) of what is on the pulley.

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