I weighed the engines on an electronic postage scale. The 16cc unit just as it is in the picture but without a spark plug is 1lb. 10oz. exaclty. No carb or muffler or ignition or prop hub.
The 21cc unit was 1lb. 13.5oz. with sparkplug. No carb,or muffler or ignition or prop hub. I will weigh the plug to compare.
Am hoping to get the 16cc unit light enough to try in a Sig 4* 60. But maybe it won't happen. I don't want a rocket just a good cheap, and cheap to run sport engine for it. Right now it balances good with a TT90 4stroke and a 16oz. tank empty. Am hoping I can go to a smaller tank and use the difference in fuel weight to compensate for the battery pack needed for ignition. Or perhaps I should check into that glow on gas thing in one of the other posts.
If the 21 has enough power it may go into a Sig 4* 120. Wait and see.
Here are pictures of the 21cc unit.