I have a original Moki 1.8 for many year's now. It's a original Czech engine I believe? Like the others have said, very strong & reliable. I run mine on 5% nitro only with 20% lube. It doesn't like higher nitro & stays pretty cool. Leaves a nice vapor trail. I fly at altitude @ 5300' & it does fine. Flip it backwards after wet primed as previously mentioned and it kicks over in the correct direction due to all the compression. I've gotten the few parts I've needed from "just engines" in the UK. I don't use a fuel pump, just larger fuel line, on supply & pressure, & it does fine in all manuevers & attitudes. It's in a 120 Stinger weighing 17 lbs 2 oz. Not quiet unlimited vertical, but pulls upline very well. If I was at sea level, I'm sure it would scream! I'm using a "Menz" 18 x 8 prop, getting 8800 rpm tops, leaning to 8600 rpm for flight.
Good luck. It's thursty, but powerful!