Haven't touched the cylinder head, valves with OHV lettered cover, or cam shaft. Maybe the throttle linkage wire that I couldn't find fell inside the valve cover?
The things I have done/ touched are: changed oil, changed gas, removed and cleaned carb, replace spark plug, mod kit step 1 (jet, filter, exhaust) and removed and reinstalled the pull cable.
The pull cable is feeling fine. Just the initial knocking and stalling / idling and noticeable loss of power when riding.
so i would be looking at three areas here
1) spark plug: if you got one that is longer, the piston could be hitting it
2) carb: could have a bad gasket or idle circuit, etc. in addition to your rotation problem
3) flywheel could be hitting something like others have said
If this was my engine I would personally do the following:
1) remove spark plug, check gap: is it smashed on the end? should be approx .030" gap. Shine flashlight into plug hole, is there a mark on the piston from the spark plug? Keep spark plug out
2) carb: remove bowl, jet, emulsion tube, and idle pilot jet. clean the rest thoroughly, Check users manual for gasket placement. Make sure all gaskets are good, and there are no cracks, and especially make sure that the gaskets are not upside down or backwards. torque to spec when reassembling.
3) after you removed your spark plug you can EASILY turn the engine over because there is no compresison build up. Take the blower housing off (its the cover that the pull start connects to). grab the flywheel with your hand and rotate it. It should rotate easily in either direction, but rotate it the way the engine should spin. if it is being held up still, you need to check the clearance that the flywheel has to the magneto (coil gap) should be about .0166" from the flywheel magnet. The magnet attracts metal, there could be a screw or nut or something made of steel stuck to the magnet on the flywheel that is rubbing or nudging the coil.
If you are still having issues, you may have to actually open up the crankcase and see whats up. Chances are, you messed something up yourself, even if you don't think you did. Ive had plenty of those moments, where i was like "im an idiiot why didnt i think of that" we are all here to help you out so the more you can tell us, the better chance we have of helping you out.