In order to remove starter from 86 trail boss 250,. the pull start cup must be removed. It sits behind the pull start unit when it is removed. My question is about the mounting bolt. It is not coming loose with a good amount of pressure on the wrench, and I fear breaking it off in the crank. Is it possible that it is a reverse thread, or just so old that it is frozen ? Any insight into this problem is greatly appreaciated.

 

This is where a heat gun and penetrant along with a 3/8 air impact would help on frozen bolts.