I just purchased an 2009 MEP-803A. I rolled the dice and bought a model that wasn’t test run bc it was missing a couple fuses. When I picked it up it was also missing the exhaust flap..unknown for how long. I’ve manually turned the motor over via the fan bolt with a socket. It moves smoothly for multiple turns until it hits a sticking point…that can’t be turned past. I don’t want to force it and do more harm. Thoughts? Could I have the top of a cylinder rusted? I removed the exhaust and see minimal soot, zero rust in the manifold. Engine only has 300hrs. All fluids were already drained when I purchased it. No water or additional oil came out when I attempted to drain before adding new oil. I’m stumped. Thanks in advance.