I use PB Blaster. My (deceased) father-in-law had a gas powered welder mounted on the back of his work truck. Sat in the weather (exposed) for at least 5 years. Engine was completely seized. Mother-in-law said someone made an offer on it but only if it ran.
I got a couple cans of PB Blaster (available at just about any auto parts store, and I even found it was Lowe's Home Improvement).
After the usual Mother-In-Law smartass comments that it'll never work, I sprayed the spark plugs, let it sit for an hour, and then rapped (e.g., hit) the plugs with a small hammer and waited another half hour. The plugs came out. I then filled the chambers with the PB Blaster, AND poured it into the exhaust ports and waited until the next day. I rapped the crank with a hammer (note that I said "rap" not "beat"), buttoned it all up, and said to wait one week.
The next week, I pulled the plugs and uncovered the exhaust ports. The engine turned.
New plugs, new motor oil, cleaned fuel system, clean fuel, rebuilt carb, and the engine fired right up. I invested about $20, mother-in-law "earned" about $500.
Did I get "thanked"? No.
