my nemco 6805 runs for about ten minutes the the conveyer stops turning

[fixbear]

I can think of several possibilities.

1.  Motor bearings or brushes may be at end of usable limit.

Or

2.  The toaster reaches the top of setting causing the high limit safety to trip.

Or

3.  The conveyor belt drive has something interfering or creating a resistance like a bad bearing or some foreign object wrapped around the shaft near the bearing  or the chain is frozen.  Any one of them will cause the motor to overload.