I don't think this giant Sukhoi will be started soon, although I did just end up with an engine big enough for it.
Against my better judgment I troll around on eBay for deals occasionally, and stumbled upon this Quadra Aerrow for sale. The size wasn't listed and the seller knew nothing about it. My Google-fu was weak and came up with very little info about the Aerrow twins - I could only find enough to suggest it MIGHT be a 198cc twin... HUGE! I have absolutely no need for an engine that big, but with no other bidders I won the auction for a very reasonable amount and I figured it'd be a fun project.
Today it arrived from Canada, with some pretty poor packaging, and it's NOT the 198cc engine. The jugs on it are almost the same as a standard Quadra 50cc uses, so my assumption is that this is really a 100-ish cc engine, perfect for the Sukhoi! One spark plug was broken in transit, but otherwise it appears to have survived. It's got TONS of compression, rotates smoothly, and the ignition appears to be in good shape. The mufflers are kind of funky looking, but as long as they work I'm happy. It's got a mechanical ignition advance, the carb moves freely, etc. I'll replace the spark plugs and set it up on my test bench to see if it runs.
I called a guy who specializes in older Zenoah and Quadra engines who was helpful, but he said he had no idea what Quadra was making "back in the day". He suggested sticking with 5V for the ignition, doing a carb rebuild, and seeing what happens. He also gave me the name of another guy who does electronic ignitions for these engines, which would get rid of the mechanical advance and give stronger & more consistent sparks, so if it runs I may get a price on that. I'm guessing that'll cost far more than the winning auction price.