I just purchased on ebay (US) a great condition secondhand 10GX2, great that is except the US seller obviously couldn't get it to run when HE had bought it, I found the carb must have been taken apart and the front metal cover was fitted the wrong way around so the pump wouldn't work, easy fixed. The low speed needle was just about falling out so I followed the instruction book to set the low and high speed needles exactly to spec, as they were all over the place from the previous guy. (Don't some people mess around!)
I have recently bought a new O.S.GGT15 which is the gas engine with a GLOWPLUG, and I had a spare G5 plug which screwed directly into the 10GX2, it fired up first time and it runs great, without any adjustments whatsoever. I have saved over 2/3 the new cost by buying this non-running engine. And this is how I intend to use it. NO IGNITION SYSTEM, so saving the extra weight and no fiddling about with extra wiring. Very pleased with it, going initially in an Acrowot Mk2 to replace the previous K&B 65 sportster, that engine really hauls but is pretty thirsty.