Small Engines (Lawn Mowers, etc.): torx bolt, broken bolt, bolens

Question
When removing the torx bolt in the Bolens BL410 the head broke and the threaded part of the bolt is still in the end of the crank. What is the size and thread of this bolt? I'll have to retap the shaft. Also the torx size? Is the bolt replaceable without replacing the clutch drum?

Answer
Is this your model number, 21B121R765?  Can you identify the screw in the part lists (refer to this link)  http://ipl.ordertree.com/ipl/339/769-02638_bolens_bl410_tiller.pdf

I didn't see the screw listed but I'm guessing it is a 10-32 or maybe a 10-24.  I'm not sure enough material is available to tap the crankshaft.  I'd clamp the engine in a drill press and drill out the old bolt.  Do you have a drill press and an easy out broken bolt remover tool kit?

Eric