I have an MDS that is giving me problems. It runs good at full throttle. Runs good at idle. Does not hesitate when going from idle to full throttle. While I'm flying I cut back once I'm up to altitude and it runs fine for maybe a minute then just shuts off with out warning. After a deadstick it starts right back up and runs fine. I have read many posts here looking for some kind of help. Some times I think maybe there isnt enough pressure pushing the fuel but then why will it idle? I have considered a fuel pump but dont know enough about them. I would think an engine like this would run fine without one. I have pressure tested the tank and fuel lines under water and found no leaks. The engine is fairly new. Any ideas?

What size MDS do you have?

MDS typically take a tank or two, sometimes three to properly break in.

You dont have your tank too low int he plane? Or too far back? that sometimes leads to fuel sucking problems..

Its a .58 in a Tower Hobbies trainer. The tank came with the kit and fits into the cut out in the fuse.

If the tank is installed very tightly it can cause the fuel to foam in flight, try wraping in foam rubber. Some fuels foam more than others, and the airframe vibration is not the same in the air as on the ground.

Jerry

Your low end might be too lean. At idle, point the nose up for about 30 seconds and see what it does. It should stay about the same, maybe gain a little. If it increases alot, you are too rich, if it decreases then you are too lean or you have a fuel draw problem.

I have foam around the fuel tank, I glued foam strips on the formers so I could slide the tank out later if needed.
I have tilted the nose up thinking maybe it was a clunk problem, keeps idling. I have sqeezed the hose at idle listening for increase in speed. I adjusted accordingly. At idle I smack the throttle stick full open. It does not bog.
I set the top end needle for max speed then go a few clicks rich. I readjust both needles after making a change and test it nose up and full throttle from idle. It runs good on the ground. I nail it to take off. It will do a vertical climb for about 250 feet then will slowly stop acclerating. I level off then make a lap around my field. Then when I cut back to about half throttle it runs good doesnt burble or miss. I make about a half a lap and it shuts off just like you turned the key off in your car. I am pretty mechanical and I will figure it out if it kills me but right now I'm ready to take a hammer to it. (just kidding). I am seeking advice and appreciate anybodys input.
Thanks, Mike

If it is quitting that regularly, I'd check the clunk line and make sure it doesn't have a pinhole or anything. How much time does it have? My MDS 48 took about a gallon before it started running well.

You said that you used the tank that came with the kit. Did you also use the fuel tubing for the pickup tube that came with the kit? If you did, I would change that out with some good quality tubing. I used the kit stuff on one of my first planes and it acted like what your describing. Would run fine for a while, then would start to get air bubbles in the line to the carb and just shut off. One of the guys that I was flying with asked if I used the pickup tubing that came with the kit, and suggested I change it, after changing it, I have had no more problems. Everyone I talked to at the field afterwards said they just throw the stuff that comes with the kits away, as do I now.

I put some skis on the plane today and tried to fly. I could not keep the engine running no matter where I set the low and high speed adjustments. I fiddled with it for about an hour and gave up. Later I took a hand operated air pump and hooked it up to the muffler. I sprayed the engine, lines and muffler with soapy water, then put some pressure to it. I found two leaks. One at the idle speed screw. This doesnt concern me because I can just plug the hole. The second leak which is the worse of the two is at the throttle barrel on the carb. It leaks all the way around. It has to be sucking air when running. Is this normal ??? What would you do to correct it. I looked at the parts diagram. There is no o-ring for the barrel. How is it supposed to seal???

Hi Mike ,
My name is Barry and I have seem to be seeing a lot of the MDS engine troubles being accounted to bad carbs. I don't know how old your engine is but it might be worth a try to get a newly design carb from Horizon Hobby. I have enclosed the support number for them . I am not an expert on Mds by any means I just purchased one my self I hope this helps. The number is 1.877.504.0233. Good Luck[img]i/expressions/face-icon-small-smile.gif[/img]

Barry

[img]i/expressions/face-icon-small-smile.gif[/img] Just give horizon a call! I had to call them for the same reason last week. they had me send them back
the carb, and they are sending me back a new one. let you know how this turns out . they were great
on the phone about taking care of this matter. Almost forgot I have a MDS-.40!!!!!

I called Horizon today. They said send in the old carb and they would replace it. They did not give me any static whatsoever. I took the carb off the engine when I got home from work and will ship it out tomorrow. When I get it back I will let you know how it runs.
Mike

Had two MDS one a .40 & the other a .48 I believe. Never could get them to rum properly. They were broken in on a test stand (Per dave Gereke's instructions) . Poor transition, & very difficult to adjust. Our local hobby shop stopped handling MDS engines because of all the complaints. I sold mine! I now have 3 Thunder Tiger .46s and they all run great right out of the box. You really only get what you pay for.

I got the carb back Friday and tried to fly Sunday. The carb is completely different than the old one. The engine ran much better. Much smoother and more stable. I put the engine back on my plane and took it out for a "SHORT" flight. I always do a preflight check to make sure that all controls move and go in the proper direction. I have flown this plane many times before and this time I just did a wiggle test. I'm sure you can guess the rest. Somehow the ailerons got reversed. SO for about 90 seconds the motor ran well. I now have some repairs to do. When I get this engine in some thing long enough to see how it now runs I will report back here.
Mike

Went out to the flying field today. The engine started up easy enough. I made a few adjustments to get good top speed and set the idle speed with the radio and off I went. It ran good, one fellow made a comment about more power ( a .58 on a .40 trainer takes off rather quickly). I made several laps and I was just about to think my problems were over then on about a quarter throttle it stalled. I landed without any problems. Upon restart I could not get the engine to pay attention. It would snap to life, rev like mad at top end then return to a slow steady idle. I would taxi onto the field, wait my turn then advance the throttle and it would stall instantly. I did this 5 or 6 times making adjustments in between to no avail. I hate to badmouth, but I am not having any luck with this engine. This is the second one I have had and it does the same thing. I am just about ready to sh**can this motor. I really dont know what to do next.

Mike,
I have a brand new mds.40 I will sell for cheap!!!!!!!![img]i/expressions/face-icon-small-wink.gif[/img] I think I will get myself a Evolution trainer engine from horizon instead. One of the guys at our field just aquired one for 80.00 what a sweet little engine. Good power good transition. And it comes almost totally broken in. Just kidding on the MDS. Happy Flying[img]i/expressions/face-icon-small-cool.gif[/img]

For the last year I have been reporting stalling problems with my MDS 148. The only certain cure has been an on board Glow Driver by Telco. I have tried three different makes of carb and every possible cure to the fuel system, but the thing still switches off the ignition in flight. On the shelf now replaced by an SC 120 Four-stroke. Not as much power but never stops.
My old Wot 4, has also suffered this week from it's MDS 58 switching off resulting in a forced down wind landing. All my MDS engines ran perfectly when new, but when run in they stop in flight. The new carb called P2 has not cured the problem. I watch other club menbers and now realise that saving a bit on cost over an OS can be expensive. My club mates with OS engines and my own OS four strokes never stop and are easy to adjust.

I will second that about the OS engines. I ran the 46FX on my Gee Bee profile for the first time in 6 months today, and it started with the chicken stick on the 3rd flip. It actually "started" on the first and second flips with a chicken stick, but it was running backwards...

The only MDS I ever owned was a .28, started easily, ran quietly and smoothly and quit in flight at full throttle so often that I finally gave the engine away. I tried everything including replacing the fuel lines, carburetor o-ring, fuel filter and glow plug. I adjusted the low end and high end mixture everway till Sunday trying to find something that would keep this thing running and I finally had to throw in the towel and give up. Amazingly the engine would run beautifully at half throttle or less and would never quit. Anyway that's my two cents worth on MDS with one exception, and that is the 68. Everybody I have met that runs a 68 MDS loves it and wouldn't trade it for the world. Go figure!!

John

I have witnessed Mikes's engine problems many times and I can tell you my Navy training in swear words comes in very handy after every in flight engine failure. I have a Thunder Tiger .61 that runs great on the test stand and is ready for flight.I also have an OS .46 that runs fine...a little hard to fine tune in cold weather but we have run the rag weed out of this engine. My question is this:
What would be my best buy for engines in the ranges of .40 to at least .80? Hang the cost I just want to avoid buying junk. I have had three MDS engines and I've never been impressed with them. Would I be better off with four stroke? If so what make and size equivelent to the same power range of two stroke .40 to .80? Dead stick down wind landings over a full grown corn field can really get the juices flowing!
Web

If you are looking for 2 strokes, OS makes the best. My 46 FX fired right up with a chicken stick after not being run for 6 months. The only adjustment that was needed, was a little tweaking on the high end since there was about a 35-40 degree temp difference from the last time I ran it. It ran on the first flip, but it was running backwards. On the 3rd flip, it ran forwards...

My previous reply was that MDS have a problem. Most of mine stalled in flight, either every flight or most. I build my own engines for fun and therefore think I know what to do to cure problems. Unfortunately my larger MDS sizes, 148 and 58 stop frequently and have resisted every attempt to cure them. The 148 is better with an ASP 1.08 carb, which fits straight in. The 58 is better after sealing the slow running needle with gasket seal. Also the throttle stop screw. Better but so sensitive to the correct mixture that it needs re-setting almost every flight. I have given up for the time being, but still keep looking at the lumps and trying to find a cure. My pal also bought the 58 at the same time and fitted it to WOT 4 the same as mine. He is still using it and after the above sealing session has managed at least one flight when it kept running! We still have the old style carbs as the UK agent is not so willing to replace them free and the cost is almost as much as we paid for the engines.
Calculating the cost of using the 148, I found that stopping in the wrong place has cost me a scratch built Ultimate, shredded through a tree, a complete fuselage re-build of my WOT 4 and a lot of dead engine landings causing minor damage. Since fitting more reliable engines I have not had one stoppage or crash caused by the engine.

One suggestion for you all! M.V.V.S. engines are truly the best (affordable). I've been flying for thirty years and have over a hundred engines. I have eight planes currently and only fly Jett and M.V.V.S. and have had no problems in at least ten years! (other than those that were my fault)

Max

I too have an MDS .40 that came with my H9 Extra Easy trainer. Nothing but problems. Although sorry to hear you folks were having trouble too, I was glad to hear it wasn't just that I didn't know how to adjust it. (Rookie) I could never get it to transition smoothly. It would run fine from idle to just over half throttle, but I couldn't trust it to keep running at throttle positions higher than this. It would just stop. It also needed adjustment after EVERY flight. I have now replaced it with an O.S. .46 and love it. I also noticed on Horizon,s site, that the Extra Easy II they just released, (new paint job) now comes with the Evolution trainer motor. Not MDS. Probably too many complaints. I will say that the MDS was a very strong motor (lots of power) but alot of good that does you in the middle of a slow speed low altitude turn and the engine stalls. Been there[img]i/expressions/face-icon-small-sad.gif[/img]