sounds like the motor siezed. i agree i think that motor should be oil injected. look for an oil reservior and make sure there was oil in it. probly gonna be a lost cause if it ran tight.
RIP 91 Polaris Indy Trail,
85 Polaris Indy Trail... 488 motor from ^
74 Polaris Colt... custom 440 motor from ^
89 Ski-doo Formula Plus (521)
92 Ski-doo Safari L (377)... still in diagnostics phase
praying for snow and for the packers