Yep, most of my engines have backfired and loosened up the prop at least once. Usually during run-in and initial set-up. For my two strokes I have been very lucky that the prop did not fly off. For my four strokes I use Tru-Turn set-ups - they really can’t fly off since they use a lock nut.

I appreciate the information guys. It looks like I really need to get the engine and prop in my hands so I can see where I am at.

I actually would rather run a lock nut on the Moki. So I called Tru-Turn and asked. Unfortunately, the tech guy confirmed that they do not have an adapter with a lock nut for this application. They just don't make a double jam nut in 10 x 1mm thread.

They tech guy also said he prefers the "0105" adapter. He says this is a big monster adapter with a big monster 3/4" nut - appropriately sized for the big Moki. The "0100" adapter is sized for the 1.80 engine and he says they are not as strong - Darn it. He even mentioned that the "0100" adapter is less than half the weight of the "0105" adapter ... which weighs a whopping 2.2oz all by itself. This is going to be a heavy set-up.

So I'll order up the engine and see what it looks like.

So far I'm looking at the big "0105" adapter ($16) plus a 3.5" menz cut spinner - with the special back plate (~$80). A bit more than I had intended to spend.

If anybody has a way to get this done safely ... I'm open to suggestions. A 20" prop flying off your Moki 2.10 could ruin an otherwise perfect day of flying.

Moses