I was using the circular saw yesterday when smoke and a burning smell
came from the motor, so stopped immediately. Didn't think I was
overtaxing it at the time - just cutting some chipboard.

Today, it still runs but the motor sounds raggy and the burning smell is
still there.

What's likely happened and is it for the skip? It's a B&D so I guess
spares/repair is possible although maybe not economical.

I checked the brushes and they seem to have plenty of length left in
them.