If the engine stalls there is definately a problem. Check the two bolts that hold the clutch on. That is the most common problem with them backing off. If this is the case be careful if you still choose to run it so you don't crack the cases.
It could also be the rollers sticking but I doubt it.
Take the clutch cover off, remove the clutches, clean everything with brake cleaner and then reinstall the clutches with red loctite to about 250 ft lbs of torque (check the repair manual for exact number).