I have a 1998 MTD Huskee model 13A0673G131 with a Tecumseh 15.5 hp engine model OHV155-204508D. I had to change the engine pulley and in the process misplaced the cap screw/bolt that holds it on. The online MTD parts diagram shows it as a 7/16-20 1.25" long. I got one and it is too wide for the hole in the shaft. Can anyone tell me what size I really need?