When they were still imported by Horizon they tried to get the Russians to make or use a better carb. Horizon even started sending people what was supposed to be the new improved carb but it was the same old carb with a different number. Using 5% or FAI fuel helped them out a lot but it still didn't do anything for the poor casting of the case. They tended to break off right at the area of the muffler. I did have some luck with there .68 a lot more then there .58. The .58 I just sent to a friend never did run. I had used three of them at one point, the other two ran but the case broke in flight on them. As I was removing the needle valve in this last one I had on hand I discovered it was bent at the tip?? Factory quality. I had never removed it, by that time I had given up on them. I sent along a new carb with a good needle valve with this engine.
When they ran they were power houses but I never trusted the case after I broke two of them. I still have a .68 that ran very well most of the time, even on 15% nitro. It ran better on 5% but I only use one blend of fuel for all my glow engines.
There is a reason they are no longer handled by Horizon. I don't toss them but I do use them for parts, screws anyway. At club auctions they are give away engines.
For cheap two strokes {I use very few two strokes} I found the SK .91 a very good running engine and a good buy at $100.00 with a muffler. Same price the MDS .68 was before H-9 quit selling them.
If Vdub is willing to pay for one then I have a deal for him. I think? I would have to dig into my engine box. I think I still have a .68 plus one that was a parts engine?
Being a very old post a lot of people today have never seen an MDS engine.