i have a 1999 750 sport xi. last time i used it, it chopped up the driveshaft coupling damper. i have replaced it and also 3 of the engine mounts which were broken. i thought this would have solved the problem but when i started the engine, the driveshaft moves backwards. someone told me it may be because the driveshaft bearings are worn out. i have looked at the parts diagram [attached] but still cant see what really keeps it in place. does the impeller just slide over the driveshaft spline or is it attached somehow?

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