stroke increase 600 to 650

The conrods on a 650/750 engine are actually shorter than those from an 88 99 motor.

Done with a bigger crank throw, which needs a bit more space in the back of the case. Don't think the barrels are a simple swop. Need to check clearances at bottom of barrel  and pushrod  tunnel

The 650 barrels had a large square cut out at the bottom of the barrels to clear the con-rods when the engine was running.