Hello; I did a similar thing with my good ol' Saito 45, it wouldn't turn either. I took off the back cover and used a wood dowel to smack the crank centre forward. That took the side thrust off the connecting rod and solved teh problem. I have used that engine for years since with no problems at all. What happened was the spinner slipped allowing the crank to slide back until it couldn't go any farther without breaking the connecting rod or forcing the crank through the back cover. I see guys advising you to send it in and get it fixed, I guess that's good advice for a new engine, but my engine is ancient, and at least 12 years out of warantee.