I have an older MDS 46 Black Head I was told by the guys in my club I could never get to run right. I bought it on e-bay not knowing much about engines at the time. This engine seems to be a solid build engine so I was determined to figure out what was wrong with it. When I first got it it would no idle at all and just quit running for no reason. I did a search on the wed for this engine and found an article that someone wrote on MDS carb problems. It seems the early engine suck alot of air where the carb fits into the case and at the gad nibble on the carb. I went and got some red RCV silicone from auto zone to seal there trouble spot. The article also said you should have the idle bar type glow plus. After doing this and going to 10% fuel the engine runs and idles great. It is not a speed demon so I use it on my 1/6 scale Piper Cub I built.

I hope this helps