Any one with a CV auto trans, read this

Hi,
I have a CF moto V3 250 with about 8K miles on it, I have added the MPR exhaust and e- clutch, I am running 18gr, rollers. With this set up it runs great (BUT) this is what you should know. I have checked my belt often and it looked good with very little wear.(WRONG) The standard belt will stretch and this is what could happen as it happened to me.I was doing about 50mph on my way home from work and it felt like my belt broke, I pulled off the road and removed the side case, to my surprise the output shaft on the motor broke off just behind the veriator. When I got the bike home and removed the motor and had a chance to review what had happened I came to this conclusion.
The stretching of the belt is what caused the problem,and hear is why. As I was doing about 50mph at the time the clutch was open all the way and the veriator was closed, when I closed the throttle the belt area that was on the clutch ran around in to it's self giving a hard pull on the output shaft on the motor, and snapping it off. The torque that was in effect was caused by the forward momentum of the bike and the reversed reduction of the drive belt.My conclusion is if you have a standard belt look to change it at about 4K or 5K or before, the Kevlar belts should go much longer but I have not had one so can't comment on that. I had thought I would just pass this along. Now back to replacing my crank.
Thanks
Bill