Help: coarse and fine threads on crankshaft/PTO for 787

[Bogamilsan]

Hi,

I bought a used 787 rotax replacement motor and it had (i think) an HX PTO flywheel on it (the one where it is a clutch instead of a female spline to receive the driveshaft). My original PTO was from a 1996 challenger motor and does not fit the threads. I'm guessing the HX motor's crankshaft is an odd ball with coarse or fine grain threading. Does anyone know? Also there is a regular PTO flywheel that can go on the HX motor?

Any help would be much appreciated!

 

[mikidymac]

The HX is a 720 not a 787.
All 787 crankshafts use the same threads.
It could be from a 1997 XP but again 787’s use same threads.

 

[Bogamilsan]

Thanks for the reply! I'm probably wrong on the HX.

I guess these motors are living proof that threads on some 787 are fine. I did some more digging and this youtube video shows the same problem:

.

This thread also mentions rare 1995 xp 787 motor parts: 95 XP800 Rebuilt 787 Bottom End

I guess I will try to get the fine thread PTO from somewhere.

 

[mikidymac]

From what I can find the 787 RFI and 787 Carbed use different cranks but it appears that all carbed 787's use the same crankshaft so threads in theory should be the same for all carbed 787's.

 

[Bogamilsan]

It's a mystery plot that I wish I weren't a part of... Here's another thread I found where someone seems to know that 1995's have fine threads: 96 XP 787 Bottom end rebuild question

Good news for me is that my old motor might have been the odd ball out, and my new-to-me motor seems to have the coarse thread shaft. Anyone have a cheap coarse thread PTO laying around?

 

[mikidymac]

Check with Nick or Jess at Westside Powersports Seadoo. Westside Powersports

 

[Matt Braley]

Yes the 95 XP800 787 has fine threads and requires a different pto then the later 787's. It uses a different counter balancer also.

 

[Bogamilsan]

Thanks everyone!

 

[Chester]

...All 787 crankshafts use the same threads...

Except the 95 XP.

Chester

 

[mikidymac]

Except the 95 XP.

Chester

Thanks Chester! Always learning something new.