Export thread

I have a Bolens 831 with 11hp Briggs&Stratton. I can´t find out if this was a tractor that was only sold in Sweden, because it should have 8 hp. Don´t think it´s a replacement. Does anyone know anything about this combination?
The problem is the normal 65 " belt doesen´t fit. When I engage the blade it chokes the engine. The belt must be to short.

Do you have throttle at full position.