jriebold

Ok I have learned nore about the MDS40 in this post than I have raading the manual. I too would like to give the engine a chance. I sent the first back to Horizon when my instructor could not keep it running on my XtraEasy trainer. I few a KB 40 on the trainer that a friend gave me and I never had any problem. I learned to fly on the Xtra and the KB engine combo. I recently took the replacemnt MDS 40 out of the box and am trying to get to run.

I now have learned about the fuel (5%) and the long reach idle bar. Please tell me how to run it in on the test stand. Please be specific as to time on and off, how long rich and how long lean, what RPM, what prop, how many clicks should I move the needle each time, and how do I set up the low side? Also I guess that I have a stupid ear because I cannot tell the "2 cycle and 4 cycle break" because the engine either quits from too rich or too lean.

Thanks all

phread59

I hope I can remember all your questions.

Prop- a 10-6 is a good place to start. I like APC's.

Mount the engine to the plane and use a hold down or use a test stand to mount it on to break it in.

RPM- I never worry too much about that. I break it in at 1/2 throttle most of the way. I only go to full throttle at the end.

I only move the needles about 2 clicks or so at a time. Start at 2 1/2 turns out from closed on the high speed needle and about 1 1/2 turns on the low. The manual may give more specific suggestions. Go with mine only if the manual does not supply the info. Usually the low is close from the factory.

As to how long. I go 5 on and m,inuits off for the first 2 to 3 tankfulls. Then it is by the tankfull. adjusting as I go.

Lastly to get the rich mixture. I just fire it up and adjust till it runs ok. I run it to max rpm and get it close. Then I richen it about 1 full turn. It is running real rich then. occasionally I add some more if I need it. I back it off towards lean only after 3 or more tank fulls. Remember the low speed needle is what you run on over 2/3rds of the time. spend your time on the low speed first. Always shut the engine down to adjust the low. And run it to full throttle for a few seconds to clear any puddled fuel in the engine before checking or adjusting further.

If you feel uncomfortable doing this I highly reccomend you get some help from an experienced modeler. good luck.

Mark Shuman

Stripes

My Feedback: (19)

Yea I know, all the smug answers like use FAI fuel and your problems will go away. This is a tough engine to get right. I have four MDS engines and the first three were perfect. The fourth is a stinker. Try using Dub Jett's way of adjusting, it helped me.
http://www.jettengineering.com/tech/techcarb.html
I found my 40 to be very difficult. It seems to need a special plug. I'm using a Fox Miracle Plug. It is happy only in a very narrow range of needle settings and the idle setting greatly affects the main needle and vice-versa. I am also using 5% Omega fuel because FAI is not obtainable here. All and all this is a tough case. I have mine running but the top rpm isn't very high ( 11,500) and the low isn't very low ( 5,500).

Perhaps I can get a hot two cycle plug (OS A3) soon and see what that does. This engine does very differently with different plugs. The Fox plug isn't the highest in rpm but seems to keep the engine running.

Stripes

My Feedback: (19)

Incidently, my engine's idle setting is within one eigth turn from rich to lean and the main needle is one quarter from rich to lean. Outside these settings and it is junk. (Yes, I have checked for air leaks at the carb and back plate.)

Tired Old Man

My Feedback: (1)

Better idea.

Since MDS engines are no more, and parts availability is limited to what is left on the shelf at various shops and distributors, get rid of the engine and get another of the same size from a better established, and higher quality manufacturer.

Some suggestions are: Tower (cheap engine), OS (usually good engine), Irvine (excellent engine), Thunder Tiger (good engine), Magnum (a so-so engine), SuperTigre (excellent engine), and a couple of others.

davidinmi

I got two MDS engines at a swap meet last year for $20. The .46 runs so well I could hardly wait to get the .40 on a plane. After 10 days of tuning and dead-stick landings I solved my problems with the .40. I gave it to the guy next to me at the flying field (he needed a muffler pressure fitting) and put an old OS 40LA on my plane.

Sergeant

I got a mds 40 as my first engine but it kept cutting in flight.(when it got flying[:@] ) Im now on my second mds40 chich runs really well on a 11x7, enya no.3 plug and 10%. I find the carb very sensitive to adjustments. When you do get it set DOBT change it. it shouldnt need changing unless you put it in another plane. As for the low end start the engine and run it up then let it idle for a minute or two. Then rev it up, if it dies open the low end needle 0.25 of a turn anticlockwise. keep doing this until it throttles well. Also the engine takes a lot of running in.
Tom

Fastsky

MDS owners at our club have given up on them oand gone to either Thunder Tiger or OS FX engines, One pilot was always crashing when his MDs engines quit on him. Since he switched to OS FX engines which keep running he has become a much better pilot.

DadsToysBG

My Feedback: (35)

Send it back and ask them to exchange it for a Evolution 40 they always work. Dennis

Fastsky

I recently bought an Evoulution 61. It ran good out of the box and is picking up more power every time I fly it. If you go for the Evolution, go for the 46 over the 40. They are almost the same price and the exrta power is always nice to have.

changed

If you want an MDS engine to run give it legs!

skate5290

3 steps

1. take engine off plane plane

2. throw in trash

3. empty your trash

lol

i have this engine too it seems to start after a while then it won't cut off if anybody reading this thread is considering to get an MDS save your self teh hassle and look into the quality engines like o.s., saito, thunder tigre

vdubin64

My Feedback: (3)

I happen to love my MDS engines, I wish they were still in production.. I own probably half a dozen of them at the moment ranging from 40 size to 60 size. I've never had a major problem with any of them. in fact I recently purchased a .40 for around 12 dollars on Ebay that had been involved in a crash and had a cracked case near the carburetor.. I basically bought some permatex black and sealed it, and it has absolutely 0 problems running.. Don't get me wrong, I love my OS engines and Saito engines as well ... But MDS has treated me equally as well ...Now dont get me started on Magnums... Now those are Garbage !!

Gray Beard

My Feedback: (-1)

The thread is from 04. MDS was such a marvel that Horizon dropped them in about a year. I just gave one of my last .58s away but it's nice to find someone willing to buy them. Need a .68??

bchapman

I agree. I'm about ready to trash mine. I don't think the Russians were known for the quality of their engines.

I just got back into the hobby recently after a 20 year hiatis and have a Hanger9 Xtra Easy RTF circa 2000 with a MDS 40 PRO engine. The plane is great and I wish they still sold them, but the engine has been nothing but trouble. I'm fine with the flying part of the equation, but I have to run mine at full throttle in the air because I can't guarantee that it'll stay running if you pull the throttle to idle. When I turn final and idle the engine I know that I'm committed to landing. I'm gonna get a old OS 40 FX or maybe an old K&B 40 for this plane and be done with it.

Gray Beard

My Feedback: (-1)

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.

bchapman

Maybe the 5% nitro fuel would help. All I can get around here is 15 nitro. I've been running the Byron fuel that they sell at Hobby Town. I'm just going to give up on it and buy another engine. I really like flying that Xtra Easy and I don't want to crash it because of that engine. Especially after your said that the cases would break. It's no surprise though. There's probably all kinds of hidden defects in those castings.

Thanks for the advice.

Brian

Gray Beard

My Feedback: (-1)

Poor casting and a very big heavy muffler. I only use 15% and by the time it hit me that the MDS being made in Russia was probably designed for FAI fuel it was too late. I quit using them. When they run they really are a strong engine. I used the .68 for a year or better. It did have Many Dead Sticks but nothing like the .58s. They also take a lot of break in. I had one of the .58s that broke in great then the case broke. The next one they sent me didn't run very well and the case broke right away. The third one just never ran and that's the one I just discovered the bent needle valve. As I recall they came with a head shim to lower the compression but I never tried one.

Roo Man

My Feedback: (1)

What do you want for the 68?

I got one on a H9 Twist bought from my LHS. Did not know that parts were not available but did get lucky because it runs like a champ, easy to start and is very strong. It did not look like it had been used much.

Gary

Gray Beard

My Feedback: (-1)

Make me an offer I can't refuse plus the 10 beans for shipping and I think I have a complete one I was using before I moved here plus one I use as parts? Screws. I will have to look in the box. The one I was using was runing very well just before I moved here in Oct. of 06 Last time I had it in hand it was still rolling over smoothly but that's all I can say about it. Shoot me a PM because I will be at the post office tomorrow shipping out my radio for repairs.

bchapman

Just an update to an old thread:

The MDS 40 has been at the dump now for over a year.

I bought a OS Max 46AX and have never looked back. I haven't even had to adjust the needle valve once after break-in.

propbuster

My Feedback: (1)

I had one, what a piece of Junk! MDS stands for Metal Doorstop!!!

j.duncker

My Feedback: (2)

MDS did produce a few real dogs but if you got a good one they were powerful and with a really reliable throttle. Run an Enya no 3 plug, no more than 10% nitro and less if you are flying in hot conditions. They take a while to run in. Most of mine needed an hour before the throttle response became predicctable. The exception was the 38 which seemed to be good right out of the box. I had two in helis and they were both good.

The needle is sensitive, unlike some engines, adjust by 1 or 2 clicks at a time. Once it is set LEAVE IT ALONE unless conditions change radically. My 38s and 148 would be 2 to 3 clicks richer in winter.

I used to get in trouble from the club safety officer. I would never do the classic nose up test, just flick it into life then take off some times straight into a prop hang. Told me I was setting a bad example.

RCVFR

My Feedback: (7)

Over a year's time, I bought a couple of the 40's used, for cheap, because everyone knew they were no good. Funny thing, when they were retuned and run on 5% fuel, they were great running engines. Guess I got lucky. Also bought a .48 (for cheap) which turned out to be an exceptional engine.Earlier, I had a 1.48 that was a strong, sweet running engine. That one I had bought new, and it did not disappoint.