Sorry man, thats the 2 worst oils you could have used.

Lawnboy is sludgey and leaves all kinds of gooey deposits on the ring grooves during the break in process. Would have probably been okay if you'd switched to a good synthetic and mixed it at 50:1 or 40:1. The synthetic would have possibly washed some of that sludge out of the engine.

Instead, you picked one of the worst oils a guy could have picked and mixed at 100:1. The Amsoil mixed at that ratio leaves no room for error. There's no extra oil there to help break down and wash sludge out of the engine. 100:1 is not enough oil to lubricate the engine properly and definitely not enough to help remove the Lawnboy sludge.

I'm going to look into my crystal ball and make the following prediction:
The ring is stuck
There's hard carbon sludge in the ring grooves
The piston skirt has excessive scuffing
The cylinder plating is worn through
The top of the piston has hard carbon on top

Basically, it's hosed....... big time hosed.

Have it rebuilt. This time, use a better quality oil, like Penzoil Air Cooled and mix it at 50:1. Really ANY high quality oil mixed at a reasonable ratio. My crystal ball says you'll wreck that engine before it needs another rebuild.

100:1 is the equivalent of a shot glass of oil in your 1 gallon gas can. Thats not enough oil. An engine needs more oil than that. Oil not only provides lubrication, it helps increase compression and seal, delivering more power. It also carries heat out of the cylinder and to the exhaust system.

Sorry to be doom and gloom. Thats my honest opinion. Good luck with the engine.