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If your engine RPM runs close to the critical vibration point cranks can break. Yamahas had problems with this in the past and the only way to help it was to change the mass of the crank. i.e. lighter or heavier flywheel was what they changed.
 

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Sorry to hear about your bad luck. This probably could of happened for one of two reasons.Either pto bearing failure, which the older xcr's &xlt's are famous for or something else let go in the bottom end that would cause a bad enough vibration to snap the end off. Do you spin the engine higher than factory rpm? If you do , this will add to the problem. I was in at my buddy's crank shop the other day and he had 3 of these piped engines there with the same problem as you. Also check all of your oil lines for kinks or obstructions.
 

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Sorry to hear about your bad luck. This probably could of happened for one of two reasons.Either pto bearing failure, which the older xcr's &xlt's are famous for or something else let go in the bottom end that would cause a bad enough vibration to snap the end off. Do you spin the engine higher than factory rpm? If you do , this will add to the problem. I was in at my buddy's crank shop the other day and he had 3 of these piped engines there with the same problem as you. Also check all of your oil lines for kinks or obstructions.
 

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your sled seems to new for this, but polaris's are known for not making the oiling holes for the bearing big enough, also pipes and beating on your sled can cause it too

Remember: DON"T HESITATE.........ACCELERATE!!!!
 

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hotrod is correct. First question would be does the sled have aftermarket pipes? Manufaturers tune their engines to run in a particular RPM range. However adding pipes that shift the operating RPM can move it to a point where harmonic vibrations can snap cranks.
 
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