I know what you mean I tell you if I ever find that black hole in my shop I will be a rich man.I dropped a 4-40 nut on my shop floor today. No idea where it went even though I searched and searched. Probably joined it's 1000's and 1000's of siblings that reside somewhere in my shop.
The 3W engine problem is not going to well. Striped it out of the pattern ship plane mounted the engine on the test stand and it is doing the same as what it was doing at the field. Checked the ignition got spark. Fuel is getting to the carb it is sucking it up. Checked the spark plug looks good no grounding. Got spark, fuel and air it should run but it does not. Looks like there may be something wrong with the carburetor or the Reed valves. Going to open it up and have a look.
When it is being chocked it will just burp, then switch the choke off and try to start it it will just burp for a second and that is it will just not run.
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Just a hunch but it seems the timing is way off. Pull the prop hub shaft adaptor nut and see if the hub has moved on the crank shaft.
A bent or sheared key could be the issue.