I recently picked up a 96 Polaris Xplorer 300. My buddy and I rebuilt the carburetor, got a new spark plug, and cleaned fuel tank and put fresh gas in. It ran great for a couple of days. I was riding it and it started to sputter out and lose power. I turned around to get back home but it died. Tried to crank it but the pull rope was completely stuck. I pushed it home and started researching/googling. I figured the motor was seized! I read somewhere that if u could get the wheels to spin freely that the motor would free up. I picked the backend up and slammed it down and the wheels unlocked and pull rope was unstuck, however the pull rope now pulls easier and still will not start! I read somewhere someone had a similar issue and it wound up being the crankseal. I replaced them but it still will not start! Any help would be appreciated! Thanks

 

Probably wasn't a crank seal problem in your case(good that you replaced them though),sounds more like a piston seizure from a worn out piston and rings. Especially when it looses power and dies. Engines can lock up and then free up also when they cool down when this happens. When the recoil starter become easy to pull is another indicator.To make sure this is the problem do a compression check. Anything under 100 psi is not good. Top end can be remove in the frame but be sure to check for any up and down play on the rod or rough feeling crank bearings as you turn the rod or a rod kit and crank bearings may need to be installed also. Cylinder needs to be measured for the over size piston needed and the cylinder bored and honed to match it along with new head and base gaskets. Premix the first tank of fuel 50/1 to help in break in. You probably just bought a machine that had been needing a new top end for some time and it finally seized. Saw this happen a lot to people after buying used 2 strokes and don't blame the machine on this. Wiseco is the best aftermarket piston for these also.