I purchased 2 MDS .48's and started the break-in process. I must have at least a gal and a half through it by now. I started out with short rich runs, then longer rich runs. It will idle all day and run full throttle, but midrange is still way rich. Done the pinch test on low end and high end, seems OK until I go to transition. Another thing, if I do get it to transition good a few times, then I go back to wot it's too rich, just after the needle seemed perfect. Almost like it cooled way down at idle, lean it out, then have to back it off again. I tried dif glow plugs, and found the mccoy 55 to be the best.

The reason I'm asking for advice, is because I recently read 2 posts raving about how reliable their .48's were, and they needed to be really broken in. So, this afternoon, I took the most run one out of the box, and proceeded to re-run it in, and still the same problems! I have 3 .68's also, and they didn't need any special 2 gal break-in. What the F am I doing wrong?

One i worked on wouldn't run well till i got a Macs muffler for it. Mostly i think it needed the back pressure. I hear it needs lower nitro too

The Macs for a OS 46FX fits it. They do have a little more back pressure, therefore good fuel draw.

Could you just try setting the High needle correct and the low a little lean to see what your mid range does?

Another thing is that if the spring is missing or weak that fits behind the carb barrel, The barrel will flop in and out and make your mixture be all over the place?

The MC 55 uis supposed to be like the OS #3 and #8 but there may be some difference in yours?

Good luck,

Jim

Sounds like your low end needle is a little rich. Just a note my MDS .46 manual states that the low end needl e shouldn't be touched until at least 2 hours of run time.

Pal of mine found the perfect cure for his MDS 58.................,He put it under a 200 ton press, and now it's a lot wider.
Seriously, here in the UK they are a pretty much hated motor.

Pretty much here too. You can get them to run well, but it ends up cheaper buy a better engine. The value of a good saturday is too high to be looking to save a few bucks on an MDS IMO.

Lets face it, once in a while an MDS preforms well and it's owner is so surprised that he raves about it in these forums. I guess if you want the extra cost to brake it in and the countless dead sticks you deserve a good engine once in a while and obviously must feel compelled to brag about it , or are you just relieved? There is much better stuff out there for just a few bucks more, or do you enjoy the agony of defeat?

A big Yup to that.

Try a TT 46, Irvine 53...Great engines They won't break the bank, or give you headaches.

Actually I thought it/they would behave like the .68's.

The gentleman is asking for assistance not comments about his choice of engines.

That's the way it should be Brew but engine bashing doesn't strain the brain as much as constructive assistance and advice does.

Ive always heard that the carbs were leaky.

Rsieminski, Don't throw those engines away!!!. Sell them to Homebrewer and Hobbsy.

....I've seen engines that had to be peaked....and not
richened up....to transition at all. That's just they way
they are.
Peak it up, and run the snot out of it....if it doesn't
cooperate....put it under the press....

I have more engines than planes at the moment. My last MDS I bought was a MDS .58 for 33 bucks. They guy couldn't get it to run right and blamed the design/carb, etc.etc.. It was just a couple of loose head bolts that caused the engine not to idle correctly. I guess that was MDS's fault, huh?

I have more engines than planes at the moment. My last MDS I bought was a MDS .58 for 33 bucks. They guy couldn't get it to run right and blamed the design/carb, etc.etc.. It was just a couple of loose head bolts that caused the engine not to idle correctly. I guess that was MDS's fault, huh?

not knocking the original poster, but Its my experience that the modeler is always at fault one way or another. Some folks shouldnt be allowed to own fuel burning engines. my mds 78 is wonderful and a powerhouse.
love it. buy another? not likely. I'll stick with supertigre.
d