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So I couldn't get it going yesterday... It fired but couldn't stay running. Glow plug was brand new. I ripped off the fuel filter (clean anyway) looked in the carb and decided to clean it. When I went to put the carb back on I noticed a little small o-ring. Does this go on the engine part and gets squished by the carb as you press it down? I'm sure i have it in the right place. I'm not sure where else it would go. I felt something fall in my lap while i was working on it and I didn't see where it fell from.
Also, should the carb be able to spin around after the pinch bolt is tightened? It seems secure, but I don't feel like that's supposed to happen. I don't want to overtighten it and break something. I read somewhere that I should use RTV?

Use Permatex RTV automotive, O2 sensor safe silicone at the carb base around the O-ring and press the carb down while you tighten the pinch bolt

Bump.... Is the carb supposed to spin or no? I've got it pretty tight. it doesn't spin easily, but if I turn it pretty firmly it will turn. I really don't want to over tighten it and break something. I usually never let my stuff sit and let crap build up- hence never learning how to clean and take it apart lol.

Carb is supposed to be stationary and NOT spin.

With that said, you should probably use some RTV (sensor safe) where the carb meets the case - it doesn't take much but my guess is that it will leak since it's obviously not getting super tight. A dab around where you tighten might help a bit too.

Also, be 100% sure that the carb linkage angle is correct before you add the RTV.

Let the RTV set (overnight) and you should be good to go!