This is my first gas engine, I brought this new with a spring starter already installed. Started for the first time today, it appears when winding backwards on the spring it
appears to be scrapping or rubbing against something, but this does not happen when being rotated forwards, engine starts and runs beautifully. Does anyone know what this
could be or what is causing it to scrape? I have installed this engine into a World Models 1/3 scale Piper J3 Cub and I have a 22/6 propellor, is this suitable for this engine and model?

you cannot wind them up tight. The spring coils go in between each other and rub the one way clutch and the shaft.

The front coil gets distorted and rubs the crankshaft and makes it hot. This melts the rear case seal and cooks the grease in you dog clutch one way bearing to where it freezes up

The bad seal lets air in the crankcase and your engine will not draw fuel

Is there any trick to engaging the spring starter? About how many turns should one do to fully wind the spring once engaged? Thanks!

One Turn!

I grab one prop blade at 12.o'clock,, wind it back to 6 or maybe 7 and let 'er go. If she's wet, she'll go.

I have a Quadra 40 with the same setup. If it is ready to go, you only need about a 1/2 to 3/4 of a turn to start it. I put my hand over the carb and turn it a few times for priming. Then flip it backwards. Don't know about the Zenoah but the Quadra lika good prime. It doesn't have a choke. If you do happen to break the clutch bearing, you can buy one at Boca Bearings. Then press the bad one out of of the housing and press the new one in. A little heat on the housing will let the bearing slide out.

I think the instructions say no more than 3/4 of a turn. They also need periodic greasing, although I haven't put any grease on mine yet. I have found a 22X10 prop really flies my Big Bee well. The 6 pitch prop might not be enough for a big plane like that.