I read this thread and got concerned.
Thumper Central » Broken Cranks on YZ250F and WR250F Frame #'s
As far as the differences between the 01-02 and the 03, a member listed these specs.
2002 2003
Crank Web 105mm 106mm
Crank Pin 30mm 32mm
Bearing 38mm 40mm
Crank Taper 17mm 20mm
Crank Length 95.5mm 106mm
Frank - The replacement rods & bearings from Yamaha have not been a problem in a properly rebuilt crankshaft. It's important to carefully check the machined journal that mates with the main bearings on the ends of the crank . Once these journals wear the crank can't be rebuilt. The only option is to purchase a complete crank assembly. If you are going to run a used 250F at sustained high speeds like you'll see in SuperMoto it would be wise to figure in the cost of a complete bottom end rebuild as well as servicing the cylinder head. The titanium valves are only good for a couple of seasons before they start to pit and cup. The seats can be serviced by a good machine shop but the valves are unfortunately disposable.
It's a great engine/bike package, but they need to be maintained on a schedule similar to a 125 two-stroke.