I decided to run it as it is - with modified stock muffler (the inner baffle plate removed and drilled two 10mm exhaust holes). The gap between magneto wheel and ignition coil was setup using credit card.
I tried to start it by hand but no luck. The engine fired up from time to time but didn't continue to run. So I grab my Sullivan starter and the engine started after first turn. I let it run a little but when I advanced the throttle suddenly I heard a metal noise. I killed the engine and checked it out. The piece of magneto wheel was scraped. Under the vibration it just stroke the ignition coil. So even I had the original support, it still can flex under vibration. I will not weaken it even more.

I adjusted the gap using two credit cards. This time it didn't even fire then I was flipping the prop. However with starter it run after the first turn. I will not be able to start it by flipping the prop but at least my standard starter works. I can live with that.

I noticed first that the high end was way too lean. I had to unscrew it one full turn. I guess without restriction on the muffler the engine wants more fuel. After letting it warm up for 30 seconds I opened choke and run it a little.
I was able to get steady idle about 1800-2200 rpm (it is difficult to set it using flex linkage held by hand, and reading the rpm with the other).
Full throttle is 7200 rpm on Master Airscrew 16x8 Classic Series. Not bad for 1:30 with Motul oil. It my fuel I use to break in MVVS and Brison. I may get a little more rpm on 1:40 with Motul (my running mixture on MVVS and Brison).

I think these are good number for stock 25 dollars motor. The sound of the engine was also cool. It will be even better with Wacker's muffler (when I get it).

RysiuM