Crank sheared???

taylzee

taylzee

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Joined
Feb 6, 2006
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Flat Lands, Canada
Anyone have an explanation for a crank shearing off at the PTO bearing? I have a friend that had a bit of a sieze on his rotax. One of the guys he was with worked it loose and got him fired up to make it back to the cabin. A few miles later the primary started bouncing around because the crank shaft had sheared off at the PTO bearing.

Anyone have a similar experience? And if so did you ever find the root cause?
 

I can only imagine that the bearing is at fault .Heats up the shaft,a few hard pins later shaft starts to get weak and bingo one twisted off shaft.
 
Bent crankshaft maybe.......same thing happens to the Polaris 800's when/if they blow.

In the case of the Polaris sleds, the cases have to be setup right, too loose and the bearing will move around too much, which makes the crank wobble too much. After time it wobbles more and more, bending more and more, eventually it snaps off at the PTO bearing or between the PTO bearing and clutch.

Supposidly the '07 Ski-Doo 800R motors had the opposite problem, not enough clearance between the bearings and case.

What year and size motor?
 
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The engine rebuilders are generally good guys. They have done some quality work for others I know. They are doing the proper thing and doing it for him at no charge. I was just doing some digging to see if they may have missed something during the rebuild that I might be able to add so this doesn't happen again.
 
Not that there was anything wrong with asking here, but you might want to try at a Ski-doo site. People there might know more about it.
 
Ya, I could do that, but I thought I would just post to see if anyone knew if it could be a generic rebuilding mishap that I was missing. My guess was the PTO bearing or wrong pistons that caused the partial sieze that caused the weakening of the crank.
 
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