B&S engine crankshaft thread size

Hi I have a Briggs & Stratton engine that I completely tore down and cleaned and replaced a bunch of old parts. I got it all back together and started to put the screw into the crankshaft to hold the pulley on and the threads are mushed and unable to screw in. I’m trying to find the exact bolt size that goes into the end because I think the last person to work on it may have used the wrong thread size. The engine is model 1202120523B8 and the crankshaft part number is 797070.

Thanks!