Mine seized with about 300 miles on it - Mag side. After it had seized, it started with one pull and ran, but it did not have the high-end pull it did before. My PTO side looks perfect. I had also checked the pistons at 50 miles and 175 miles and they were fine.
If you see bad scuffing it probably seized a some point. I was talking to a friend last night, who also has a f7. He had to come over and rubbing it in that he has had not problems with his. I asked him if his f7 ever stalled for no reason. He said yes but it started right up with not problems. He said it happened when he first started one day. I asked him if we could remove the exhaust and look at the pistons. His PTO piston looked like shit. It must have seized. It looks like my Mag piston. He has put 150 miles on it since the stall has happened.
I was at the dealer today for new piston and cylinder. He said when it seizes like mine did, it is cause by the air pocket moving into the cylinder. He thinks that it happened the last time I loaded the sled onto the trailer - while the thermostat was opened. The air went up the left side to the engine instead of the right to the reservoir.
Dan E.