I would not personally use a larger sump bolt but repair with a helicoil (or timesert or your other favourite thread insert device) - it is M14 x 1.5 thread.
The easiest kit to use is the PermCoil Perma-plug system - everything you need in the kit, including a special 'stepped' tap, that threads into the original thread as a leader & cuts the new coil thread.
That means no drilling required! Plus a winder tool to insert the coil.
This is the M14 x 1.25 thread kit, but shows how the tap works
This is about the cheapest I've seen - http://www.woodys-auto-supply.com/au...d=THK-3221M14F
If you are searching, look for PermaCoil 3221 M14F
You need a 14mm size crush washer - absolutely available at just about any autoparts store.
Torque spec is 25Nm
You will need a new gasket to replace the sump pan - it does go by engine serial number so you will need correct one.
It can be replaced with the engine in position - you will need to remove the headers.
When you get a moment please add your bike info (year/model) to your profile.