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Fresh rebuild from previous owner. Took a few runs accross the lake and all is good. Point it towards the trailer and it just quit and locked up tight. Pulled the jugs to find a leaking base gasket PTO side causing something to bind up. Havent taken it all the way apart but my guess a bearing seized?

Noticed the head studs had alot of crud on them. Thinking maybe the guy that put it together inadvertantly miss torqued the head bolts? Really nice piston wash on the other two holes.

Another idea is that my torque stop on the front of the motor isnt in the perfect position. It should be installed to keep the motor from lifting up and I have it restrained to prevent for foward/backward movement. Is it possible because of the position of the torque stop that the entire motor twisted and caused the leak? Motor mounts are solid as Sears. Just thinking out loud here. I hope the crank and everything is allright and all I have to do is get a new bearing?

Kinda anxious to get inside this thing and take a peek.
 

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How much coolant did you find in the bottom end of the motor? Was it enough to cause a hydro lock where the motor wouldn‘t be able to spin because it’s full of coolant? I wouldn’t put my money on the bearings being seized just yet.

Every 650 I’ve taken apart has had rusty studs. How tight did the head bolt feel when taking it apart? I can’t remember the torque for the head bolts but it’s not a lot.

All the older sleds had the torque stop there in order to keep the center to center distance of the clutches correct so I can’t see that being part of the problem.
 

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what year is the sled?? to my knowledge Polaris never made a 650 XCR. or are talking about an older plain 650?? if it's an XCR, it's either a 600 XCR with an Ultra or XLT based motor or an XCR 700 with the Ultra 680 motor. the XLT based motors all have a solid cylinder set-up, all three are cast together. all the Ultra based motors have individual cylinders.

basic things to look at are piston skirts, any heavy scuffing indicates a tight hole, lack of oil and/or cold seizing. also are you running the oil injection system or pre-mix?? it is possible for the oil injection port to get clogged during a rebuild and not supply a cylinder oil. with the jugs off, the crank should turn if all the pistons look good. if not, you most likely smoked the PTO main bearing on crank. if they don't get lube, they heat up and lock the motor. after cooling down, most of the time they start rolling again. but they will lock-up every time once up to temp.
 

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How much coolant did you find in the bottom end of the motor? Was it enough to cause a hydro lock where the motor wouldn‘t be able to spin because it’s full of coolant? I wouldn’t put my money on the bearings being seized just yet.

Every 650 I’ve taken apart has had rusty studs. How tight did the head bolt feel when taking it apart? I can’t remember the torque for the head bolts but it’s not a lot.

All the older sleds had the torque stop there in order to keep the center to center distance of the clutches correct so I can’t see that being part of the problem.[/b]
I believe it is 18 ft/lb for the smaller nuts and 22 ft/lb for the larger nuts. They should kinda "pop" when you loosen them. Know what I mean? I just read in another thread about making sure not to use any sealant on the base gaskets. Just let the white bead of silicone (or whatever it is) that is on the base gaskets do its job. The rest of the base gasket needs to be dry and not have any 1104 or spray gasket on it. I have been trying to get my hands on some copper base gaskets.
 
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