Need help identifying this 2 stroke.

numbers on the left hand mouthing lug, . 12.91.2194



The head and prop hub appear to be anodized bronze color.

Thanks, y'all.

Those Numbers make me think MDS from Russia?

Someone's copy of a older OS design? Sort of like a old ASP

Some of the earlier Russian engines used numbers stamped into the mounting lug on the crankcase like that. It is likely a Russian made engine. Probably a early MDS variant before they started putting MDS on the sides of the crankcase. The carb on that engine looks like a MDS carb which they loosely copied from OS at the time.

Thanks. I ran the engine for a bit this morning. Not expecting it to do more than sputter a bit and die, but it ran for some 2 or 3 minutes. I had to choke the fuel off at the needle.
Any ideas as to displacement? I am thinking maybe in the area of .90. It seems its the same general size as my OS 91fx.
I dont even remember where or how i got it. Just decided out of boredom to see if it would even run.

The OS .91's are in a .61 case like the Super Tigres, right? If so it could be a 10cc/.61ci. More likely to be a .61 than a .91 based on how old it looks. It's probably ABC?

Approx the same size as my ST G90 and my OS 91.
I'll know when i prop it. I started it with a 14x6 MA on it.
Hey, thanks for the replys, gives me something to go with.
As to being ABC, i have no idea as yet. I havent taken anything apart.
As well as it seemed to run, and as smooth as it turns by hand, i probably wont.

You should be able to see through the exhaust port. If it's ringed there will likely be a bridge in the exhaust port in the center.

I'm almost 100% sure it is an MDS .61. Many features the same - though not identical - as mine which is another 10 years older. The engine lug numbering system is identical, the muffler design almost identical, the prop hub is the same profile, cylinder head fin pattern the same.

If it is like any other MDS, keep the nitro down. 10% max, 5% better. And less prop.

I had one I got it from Great Hobbies for $99.00. It is a MAK .61. It is true ABC with a sleeve timed between normal and pipe. Quite a screamer. They made a rear exhaust version too.

"MAC" is a mispronunciation of the Cyrillic "MDS" - people think the "D" is an "A", and pronounce the "C" incorrectly (sounds like "S") and arrive at "MAC". It's pronounced MDS however. And they are strong runners, in the mid teens and a little above. The carbs can be leaky, some are good and some ain't (hey, I think I've heard that song before?). The fasteners on the older engines look like the screwdriver slots were cut freehand. But they look good internally. When in doubt drop a better carb on it.

Oddly, I was fiddling with engine bits a while ago and discovered that I can swap parts between an OPS Speed .65 and my FIRE MDS .61.. so out of curiosity I recently assembled a Frankenmotor - OPS .65 rear disc intake assembly, front crank housing, and crank, and MDS .61 crankcase, piston and liner. Fore-aft spacing, crankpin dia, etc are identical*. Why you say? No good reason, but since the MDS is timed for and has a reputation for pulling hard up in the 17-18k region, but has a crappy carb and known for breaking cranks if you push them hard, I thought it might make a perky piped sport motor for .40 size airframes. All I had to do was relieve the piston skirt just enough to clear the cutout on the rear rotor assembly. I started this a while ago but lost interest, and just finished it up a week or so ago. It's too bloody cold and miserable outside to run it right now, but when I do I will report these totally useless findings.



* if there is a betting pool as to who copied who, I'll put my money on MDS copying a known killer Italian engine. Can't be just coincidence can it?

It is a "not-for-export" sandcast MDS engine made in the late 70's. The circle on the side is different from the Russian versions which have MDS written on the side. As such, it may be an East German version.

Max

It looks like the numbering on the lugs is month-year-serial number, but I've never confirmed that. Would 1981 make sense for this example? Hmm, the OP says it is 91, but it looks like 81 in the picture..?