MDS 58 pro knowledge sought

[Graham Bowers]

I just aquired an MDS 58 pro in an essentially unflown Balsacraft Xtreme. I bought it from a friend who didn’t like it, so it’s sat in a heated garage for 20 years. or so. It’s an exquisite build by the way.

 

I’ve popped an OS 55AX into it whilst I assess the MDS. It turns over OK however the carb barrel is stuck, probably just gummed – it’s in a jar of fuel and I expect it’ll free up.

 

In the back of my mind, I recalled reading less than complimentary words about MDS engines and subsequent internet trawls have come up with diametrically opposed comments from junk to good engines.

 

I imagine there are truths in all those opinions and that factors such as manufacturing variation and design changes over time are at play. I have read specifically that early carbs were problematic, for example. Also that changing the carb for OS or Irvine was practiced.

 

I’ll get it going and do some ground running, then put it into a beater plane if I’m happy with it.

 

Does anybody have first hand experience of these engines and knowledge of the history they’d like to share please? I’m a sucker for wanting to resurrect old stuff.

[Denis Watkins]

I have to comment about my club at the time I had the MDS fitted in a Precedent T180, a big solid flying 6 foot span high wing trainer.

My club abhorred the use of " nitro " and we of course used castor based fuel. The bosses insisted that nitro " rotted " your motor?

MDS came at a time for me of castor straight fuel, with no nitro.

If you flew with constant throttle use, up and down, in and out of turns, all was well, but if you pootled round for 5 minutes, cruising, at throttle up, you would deadstick.

I eventually ignored the bosses and flew the MDS with MDS recommended nitro and had no further problems.

The motor had obviously " run in " more when the time came to give in to nitro use.

Nowadays with synthetic fuel, the MDS is pretty reliable.

 

Edited March 12, 2023 by Denis Watkins

[David Davis 2]

I've never owned an MDS but can offer the following observations based upon experience.

 

1. Years ago, when I lived in England, we were given an ARTF trainer powered by an MDS 58 PRO. Being one of the instructors I took it under my wing. I could get the engine to start and run at moderate revs but it would cut at wide open throttle. With some needle twiddling I could get it to run at WOT and the mid range but it would stop if I backed it off beyond middle revs. Comprehensive checks were made: the fuel tank and pipes were changed; the plug was changed; different fuels were tried all to no avail. A Rolls Royce trained engineer altered the taper on the needle but that made no difference. In the end I gave the club a Thunder Tiger engine and the trainer went on to give sterling service.
2. Within the club was a graduate engineer who ran a small factory. He built a 1/3 scale Druine Turbulant and fitted a large MDS engine to it. Precisely which engine escapes me. On the model's third flight the crankpin failed in mid air.
3. Other members of the club had problems with their engines either not running reliably or failing mechanically, hence the soubriquets Mine Doesn't Start, Mostly Dead Sticks and Metal Door Stop.
4. Bizarrely there were some members whose MDSs ran very well.
5. The 38s were mostly alright.
6. Many owners fitted Super Tigre carburetters in the Eighties.

As a result of these experiences and observations I never bought one and if one came my way I wouldn't waste my time with it!

[Geoff S]

In my ignorance, I fitted an MDS 40 in my trainer and I think it probably delayed my 'A' test by the best part of a year because it was so unreliable.  Before I had a go at aeromodelling I'd been playing with motorcycle engines for over 30 years so I assumed that model 2 strokes were so simple it didn't matter if I chose an expensive OS (which meant nothing to me) or a cheap MDS and, being tight, I opted for the MDS.  OTOH I had an MDS 38 in a Limbo Dancer for a while and it was much better than the earlier 40.

 

I certainly wouldn't bother to spend much (or any!) time on an MDS 58.  Despite being just about 100% electric now I still like messing with engines - I just don't like the faff of using one to power my models.

[Martin Harris - Moderator]

The 38s and 58s seem to be the best of the MDS range - powerful and once sorted, pretty reliable but they do often need more running in and careful setting up than more expensive options. I haven’t found them any less reliable than any of the cheaper Chinese offerings - in fact my 38 and 58 have done most of their running in wintry conditions in hack models. 
 

With apparently lax quality control, there are sure to be duds out there but if you have a decent one it will give good service.  If you’re a novice flyer they aren’t such a great choice as dead sticks at an early stage due to poor set up or teething problems are both disheartening and potentially damaging. 
 

It sounds like you’re willing to put a little effort into getting this engine in the air and as it will cost you very little to try, why not give it a go?

[Engine Doctor]

The smaller MDS engines were better and most of the last offerings of the 40 were usable provided you didn't expect to consistently wring every once of power out of them.

My experince of the 46 /58 differ from Martin's and IMHO were not  good engines. They were  unreliable and frequently broke as did some versions of the smaller engines and the early 60. I was often asked to fix them but in the end refused to work on them and could only compare them to very early Chinese offerings.

They are not even a very good engine to make a cutaway out of as the castings spring closed when cut and snap when trying to re-assemble them . 

Edited March 12, 2023 by Engine Doctor

[Graham Bowers]

Thanks for all responses, that seem to reflect what one may find on the wider internet.

 

I’ll give it a go, following the instructions and the tips mentioned here, and hope for the best!

 

The carb is now freed up so I’ll give it a good clean, screw it back together, set it to factory initial settings and pop it back on the engine.

 

It doesn’t seem to be shaping up to be much of a flying week anyway.

 

Do I feel lucky ?-)

[Brian Cooper]

I had the unfortunate experience of owning an MDS 58. . . It was a horrid engine. 

 

Without any exaggeration, it had less power than a plain bearing OS.25 

We tried all sorts of tricks to get some power out of it but it stubbornly refused to respond. 

 

In the end, we decided it had to die. . . So we fed it some 60% nitro fuel and ran it on a 6 inch prop. . . And it stubbornly refused to die. But it was good fun trying to kill it.

 

Eventually, a knowledgeable clubmate took sympathy on the engine and confidently said he could get it to run properly. . . 

After six months of pulling his hair out, he threw it in the bin.

Best place for it.  

 

[Alan Hilton]

Metal door stop =mds

[fly boy3]

I have a super scorpion built in the seventies.  It has an MDS 40 fitted.  Still flying today, starts first time every time, and has not cut out once after years of flying.  At the time of the great MDS  debate I was told these engines up to a 40 were good, larger ones not so.  Cheers

[Paul De Tourtoulon]

I sold them in my model shop when they came out and I took a couple of .40's to test them and introduce them into autogyros, a bit of silicone on the main needle to stop any air leaks, a thing that I do with most engines even now, my normal home-brewed 15% synthetic and 2% castor and another 5% nitro, and they were fine, none of that run it in on the bench for hours rubbish just a bit rich and chuck it in the air, no trouble till it went into my CAP Mosquito, "however" it wasn't the mds that had the best of my Mosquito as I later found out after passing it on to electric (🤢) motors I didn't sell any of the other ones ' if I remember well"

but before you throw them away, try them out with proper fuel,,,🤐

[Neil67]

Similar to others, I aquired a MDS 46 in an old Wot 4 balsa model.  I put the MDS aside given various negative comments seen around the internet and I fly the Wot 4 with a Thunder Tiger 46.  Despite its age it is one of my best flying models, including some graceful aerobatics. 

 

However, just out of interest I thought I would fire up the MDS.  Unfortunately, I don't have a crank nut that fits and it doesn't seem to be a common size. None of the usual suspects fit. Advice on size would be appreciated. 

[Denis Watkins]

Try this thread size from the Ripmax Catelogue

Or maybe it is a diagram part number

 

 

Edited October 7, 2023 by Denis Watkins

[Nightflyer]

Personally I have several MDS engines of sizes which have in general been very good. There was a period when they got a bad reputation because of the grade material used for the O rings on the carburettor that would react with the fuel. At the time Ripmax replaced the O rings if I remember correctly. Myself personally I had no problems but then I also ensured that my engines were sealed properly especially around the carb body and main needle.