As you probably know I have two Suzuki-powered Toros that look a lot like yours but with one crucial difference: neither of mine is self-propelled. I'm pretty sure that they don't have any belts -- so I have no experience with that.
Sorry I can't help. :ashamed:
The Suzuki-Toro that I use a lot (the other is an almost-complete parts mower) has been a real workhorse. I keep it set at the highest cutting height and use it as sort of a field mower in places too steep or narrow for my tractor. It usually cuts grass at least a foot tall.