I have an MDS .48 on the way. I have read many many negative posts about MDS engines. I believe that any engine, regardless of manufacture, should run well if it is set up according to the manufacturers instructions. I have run engines of many different manufacturers over the years and have not yet found one that did not run well if the instructions were followed. Granted there are tips here and there that will make any engine perform better. This engine is to be installed in my Direct Connection F-20. This kit was framed some years ago, but is now ready for the air. I would like to know if anyone has run this engine with a tuned pipe. If so, what was your prop choice and why. How does it perform? I am also thinking of using onboard glow for 1/4 throttle to idle just for reliability. I will consider and appreciate all of your input.

Thanks,
Tony

I have no experience of tuned pipes or onboard glow with MDS engines, but we have been running an MDS .40 in our club trainer for about a year now. I have also read a lot of negative posts about MDS. However, our experience so far does not in anyway correspond to what I have read in those posts. Our engine has proven to be one of the most reliable, quiet and cost effective model engines I have ever come across. It is not the strongest .40 I have seen, but certainly good enough for our trainer. That is the most (and only) negative thing I have to say about it.

I have no real idea why so many others seem to have had bad experiences from MDS engines.

When I first got my .48 it did not idle or transition well but a Fox idle bar plug changed it into and absolutely perfect engine, if you can get some 5% nitro fuel with 20% oil, it will be much easier to tune. I found that it ran idled best with a 12x5 Graupner as opposed to a smaller prop most people advocate. It's a strong running so a tuned pipe won't be needed. The 12x5 probably won't be best for your plane.

I have three MDS engines. They seem to need a little more break in than most ABC engines.

Enjoy,

Jim

I ran my first MDS 48 several years ago in a Cermark F-20 ARF (maiden flight). Thinking it would run right out of the box, I ran it up for about 5 minutes, adjusting the needles to get a a stable high and low end. The plane took off, got up to about 15 feet when the engine started slobbering in mid-range and quit. The F-20 had a 20 second life span, so my MDS lesson was learned the hard way. Don't make the same mistake! Run at least a gallon through it on the bench until it is stable throughout the throttle range. I have done that with every other MDS I have (48,58,2 68's,1.48) and they've worked fine.

Warjet,

There is nothing worse than losing your bird on the first flight. Over the years I have lost a few the same way. I would like to thank the rest of you for your input. Seems to me the wise thing to do is run a lot of fuel through it on the test stand first. I don't think the 12-5 prop is a good choice for the F-20. It needs to fly FAST!!! I will post my results after the engine arrives and is run . Thank you all again.

Tony

A friend of mine learning to fly got a MDS-40 on a trainer combo. For two months we tried to get it to run for more than 1 minute with little or no success. We tried different carbs, sealing the carb to the crankcase, different glow plugs, fuel sleeve orientation, fuel line leakage, fuel draw to tank location with no success at all. We sent it back for service with the same symptums as described and was told that there was nothing wrong with the engine. After reinstalling the engine in the plane the problems existed. He bought a O.S. 46 and installed it in the plane and right out of the box the O.S. performed flawlessly for two years now. MDS is a sour subject. We never looked back.

Hobbsy told you about the idle bar plug. Adjust the high end first. When you adjust the low end, be careful not to move the throttle arm or you will have to reset the idle. Use the pinch test and the "hold the plane vertical at full throttle" test.

if it cuts out in flight, it may be too lean. This engine can run fine in a stand but need to be richened up for proper in-flight mix.

Good luck. Those are good engines, IMHO. Careful with it though; Horizon is out of crankshafts(!).

Regards.

My first engine was a mds 48, which I put in my trainer. Before I even started flying, which was only a few months ago, I too read all the negative blab about dead sticks etc.

I was so concerned I considered replacing it with another motor and not give it a chance to put my plane into a body bag !!

As a precaution I sealed the exhaust, pressure nipple and carbie throat. I ran four tanks thru the motor on the bench.

When I first started flying the motor, transition was crap and power was no where to be seen...BUT ..it never dead sticked....never.

After a bit of exposure to the hobby you learn things, and what I learnt was that I had set my idle needle open at only 1 and 3/4 turns ....way to lean for an mds.

I dialed in the idle needle which for my mds is about 2 3/4 turns out...and i make the point that despite my own bad setting that motor never quit. I also replaced the plug with just a standard plug ( though the idle bar plug seems to be what everyone suggests)...SUDDENLY...this engine is running sweet , power has picked right up..and I'm getting better economy than the OS guys....by a few minutes.

So I'd say, seal everything up, yeah run it in on the bench , but only about three to four tanks, make sure you get the idle needle set right, change the plug after about 10 tanks..and she will be your Russian love !!

My MDS 48 had a long break in period. It was a very tight engine. I also have opened my low side needle significantly. Mine is more like 4-5 turns open. I have about a 1/4" gap between the spray bar and needle. It is my favorite engine with lots of power.

I have enjoyed my MDS .48 very much. Got a free C2 carb from Horizon just for asking. After break-in, idle, transition and peak were all excellent. Engine ran very strong with no bad habits. I used 11x7 and 12x4 props, both worked well. I also have read many frustrated reports on RCU about the MDS line, so I was surprised to have this engine run like a gem. I do belive that a good pre break-in cleaning and a systematic break-in helped a great deal. My break-in routine came from many helpful posts on RCU. I tried K&B and Fox plugs with and without idle bar and thought the idle bar plugs were better over all. I ran Sig and Omega 5% fuel. I do add 4 oz. extra castor to the gallon for my break in fuel, don't know if that's absolutely necessary but it's just a personal preference. I run rich enough to see a little smoke trail in flight. I ran the engine in a SPAD and it really had lots of power. Happy flying.

I have had a MDS 48 on a easy sport for about half the season. Put about 1.5 to 2 gallons of fuel through it before I could lean it out to get peak performance. I tried leaning it out as the Mfg recomended and Had a couple of dead sticks lesson learned run rich for a while . At the end of the season I was running close to the OS 46 FX's . The prop is the recommended 11x7 with a prop nut not a spinner. I definately recommend breaking the engine in well before putting it on a plane that dosn't dead stick very well.

Please allow me to ask a question here

velocity,
Is your engine under warranty when you replace the old carb with the new C2 carb from HorizonHobby at no cost? I want to get the new c2 carb but the price is pretty expensive at around $35, which is about half the price of the engine.