I used a small .25inch pin punch, about 6 inches long, it barely fit between the solenoid body and the exhaust pipe, and I nicked a ridge into the passenger side of the roundhead slotted screw head, then a tapped it to rotate free with a tack hammer. It was mild steel, so a fresh hardened punch bit into it pretty easily.

I'm replacing them with allen head bolts, so 50 years from now someone else won't have the same problem.

The old solenoid was gummed up in the 3amp-30am switch section, DOA, for the most part. It's soaking in thinner now just to see if it can be resurrected.

Obviously this was the problem all along: not oil level, not voltage, not lockout switch. At least until I install it tonight and prove myself wrong.

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MPergiel, Walker, MI