I had a Cheyanne 2.
Vacs motors in series. Ive also had a few other portable machines.
With all machines when the vac motor goes, in reality it is the electical brushes that have gone, worn down beyond limits causing damage to the comutator. When this happens there will much sparking, noise and some smoke and the motor will stop. If you switch it back on there may be a short pop or other noise but the motor will not run.
If the vacs are running continuessly but sparking a bit, then it is probably nearing the danger zone and the brushes need changing. If the comutator is not damaged all will be okay on changing the brushes. If it is damaged the brushes could wear down rapidly (in just 30 minutes once for me) and the only solution is a new vac motor.
The Cheyanne though is a very good portable machine, but has its design issues around the vacuum exhaust area.
Dave.