Help Identifying Thread

[Brad93]

Have a thread I can't seem to identify.
It is on the flywheel/crank shaft of an american motorcycle which used a rotax engine. However unlike the european bikes that used the same engine it has a different thread for the puller to take the flywheel off.

It measures 28.89mm in diameter / 1.131" and has a thread pitch of 1.25mm however its not a very long thread, only perhaps 8 or 9 peaks and its in a recess so hard to measure exactly with a thread gauge. It could also be 20TPI measured with a whitworth thread gauge.

Zeus Precision book doesn't throw up anything that OD with that fine a thread.
Looking online it seems it could be this: UNF http://www.gewinde-normen.de/en/20-un-thread.html

 

[addjunkie]

Whiteorth are 55 degree thread pitch, most american stuff is 60 degree pitch.

 

[Brad93]

If it is that, would anyone know where to get like a standard puller or a nut so i could make one?

 

[Brad93]

Whiteorth are 55 degree thread pitch, most american stuff is 60 degree pitch.

As i say its recessed so i cant get in there to have a proper look at the thread form

 

[dobbslc]

Rotax are Austrian, I would think they would use a metric thread

If you got 1.25mm pitch that's probably it .

 

[Spark plug]

Could it be 1-5/16" x 18tpi UNEF:

http://www.efunda.com/designstandards/screws/screwunef.cfm

 

[Brad93]

Rotax are Austrian, I would think they would use a metric thread

If you got 1.25mm pitch that's probably it .

As i say, we have the proper puller for the rotax engines, but this engine was fitted on an american bike as OEM equipment, and a number of small details have changed.

1.25 pitch could be 20TPI, they are almost interchangeable that's the thing.

 

[addjunkie]

Do you have a decent lathe.....if so make a few nuts with the various options see what fits.

But you need to really try a 60 degree thread gauge. My bet would be 20tpi been american

 

[Brad93]

I have access to a lathe, whether it is decent Im not sure. Ive only ever faced things off and turned some aluminium down.

 

[Tigman]

nows your chance to grow a pair and make some nuts ! LOL