Breaking rear right wheel bearings
 

A few weeks back my son came down hard from a jump on a trail with his 150cc Xpro Storm. Immediate clacking noise in the back wheel. I took into the shop a week ago tomorrow on Saturday and they were to fix that noise and put new new back brake pads on it

Called them Tuesday. Brakes were fixed, but stated they have put several wheel bearings in the back only to have the right side break after driving it a couple of minutes. This was after 2 more days of phone calls I am going over tomorrow to see what's up.

Anybody heard of a reason that wheel bearing would be under so much stress it would break in a very short time?

Something is likely putting lateral load on the bearing. Either one or both races are not square with the other when everything is tightened down. Seeing as the bike was jumped, If the hub itself isn't somehow damaged I would suspect a bent or twisted swing arm. These bikes aren't really designed for leaving the earth.

Does the spacer between the bearings exist? If it's not there you can have issues in a hurry. Over torquing?

Spacer needs to be there to accept the torque of the Axel nut. AND, it needs to be the right length to prevent lateral torque on the inner race (as Megadan mentions).

If you have the rear axel assembled with the right spacer length and torque on the axel nut (50 foot lbs or so), the rear wheel should SPIN FREELY in neutral (on the stand). That is your test.

This is fantastic advice.