RE: Spinner question
I really don't like the idea of not using a jamb nuts on a 4 stroke, but they aren't strictly required for operation. Just be sure to check tightness often if not using a jamb nut. Without the jamb nut, there is no friction to stop the prop from leaving the shaft during a backfire. Using an electric starter in no way guarantees the engine won't backfire. Even if needles are set right, the engine can still backfire under the right conditions. I used an electric starter on a YS-63 last summer. It fired up and then promptly kicked the spinner, both jamb nuts and prop clean off the shaft. The prop flew about 75 feet and stuck in the ground. In this case the jamb nut didn't prevent a flying prop because the kick was very violent, but in most cases, the jamb nuts will prevent flying props. I'm 99% sure my kick was due to an air bubble that was sucked into the line. I guess my whole point here is if you plan on running a 4S without the jamb nuts, give extra consideration to keeping the nut tight and always start pointing away from people (which you should always do anyway.) Cheers!