ORIGINAL: swk550
I've got the OS GT33 engine, ES30G CF pipe and a home made Hyde clone isolator mount (similar to MTK's) in mine. Mine is somewhat heavy at 13#. Awsome power. Tons of vertical. I'm now using the Biela 19-10 prop. I couldn't be happier. The OS tends to want to start backwards until you get the technique down. The engine has gobs of compression. The Mintor 38 did not want to swing this prop.
I got a dynatron starter for the OS33GT. I've had a lot of trouble getting the engine to fire at all let alone start when hand flipping.
Well, guess what? The dynatron doesn't have enough guts to spool the 33GT up. Spool it up, hell, it doesn't even turn it over, on fully charged 6S lipo, 25 Volts. But it turns the Mintor 38 with no problem. The OS has tremendous compression as Steve points out, quite likely high compression ratio, to be able to put out the power it does. In addition the Bore to Stroke ratio is far more advantageous compared to other 30cc engines and the Mintor 38. OS did many things right on the engine but did not make it user friendly, at least not yet, early in the learning curve....
Edited Jan 18:
Tried again to start the engine with the dynatron except this time I choked the engine and drew fuel into the carb first. Not with the starter, it wouldn't turn when dry. Just several flips (10)
Then with ignition on, choke still on, full throttle, I flipped until I heard one pop
Then choke off, throttle back to idle and ignition on and with prop backed off to BDC, I bumped the starter. It immediatel started....HOOOORRAYYYYY!
That's my new starting procedure on this engine. Now I hope to get some serious break in data