MDS 3.5cc Marine R/C diesel
 

Anyone heard of these or know anything about them? I got one cheap and am trying to find some info about it. The web turned up zilch. It’s a rear exhaust diesel with a water cooled head - 6 head screws. I’ll post a picture if I can.

Probably the Ucktkam motors. Lots of sand in the castings which ruins the screws, and poor workmanship overall. With fitting, they can go well. I have only the .15 size combat and two piped speed motors.Apparently there is an .09 which is very heavy that will never run. When they came out in the 1980's? they were $35 to $50. Very cheap at that time before CNC machines were the norm. MDS was formed after that though, and they improved a lot.

I have an MDS .40 P/L (ABC) with over ten gallons of fuel through it in a Fox engine, so they can at least fit a P/L to last. The MDS diesel I got has been used it appears, so it should have run at least a little. The description said nothing about P/L metallurgy or anything really, but I hope it’s ABC. Ferrous would be okay, but ABC would make more sense for a marine application.

Some images I nabbed from the eBay auction.

Likely ABC, my examples were. Some motors in the pile were too loose, too tight, crunchy bearings, screws from WW1 etc. Later models were made better with the MDS name. The early ones were copies of a Rossi, as were other manufacturers. My combat one runs within 500 ripems of my Rossis. It required some cleaning and fitting. Yours looks very good.

I thought it looked promising - and for $25, it seemed like a no brainer to try it. I could probably get my moneys worth from it using parts from it in other engines. I need to find a wrap-around header so I can use the engine in my boat. Other MDS 3.5fc Diesels I found some on eBay came with a header and tuned pipe - which I’ve read doesn’t really work on Diesels. So the Russians/Czechoslovakians/Ukrainians/etc. had weird intentions with the exhaust..

A pipe would likely do something. A diesel would pull a loaded prop very well. I would not use it for parts, it will be a great runner.

This one have the header adapter and such. Old listing long gone now. https://www.ebay.co.uk/itm/Vintage-USSR-DIESEL-ENGINE-MDS-3-5DU-S-/302424384293?_mwBanner=1#vi__app-cvip-panel

I wouldn’t part it out unless something was damaged and prevented it from running right or at all. The description was about 10 words, so it’s a big gamble of what kind of condition it’s really in. It might be worn out or have a bad rod or who knows.

I am into weird stuff - like the Merco .29 I took a chance with. Thankfully the MDS was less than 1/4 of that horrid piece of work.

I got the engine yesterday. It seems to be in fairly decent shape. It’s got some runtime on it, but hasn’t been ran in a LONG time. It has compression, but not a ton - it is indeed ABC. The contra is in the head and is brass. I’ll need to do some work to the contra as it’s stuck in the head pretty good. It will not move at all. Otherwise the rest of it cleaned up
decent and should be in decent enough condition to get it to run. That is if I can figure out the odd carburetor. I’ll add a pic of that soon.

Here’s the carb. The high speed adjustment is a little bit of an enigma on this one...

Looks like in flight (float) mixture adjustment or something. Good luck figuring that one out. Maybe the instructions are in Russian. That will help.

No instructions. What you see in pictures is what I got. I’ll need to find a wraparound exhaust for it too. My boat really needs a FIFE arrangement, but I can make something work with a little finesse and some parts.

I’m gonna see if I have another carb that will fit. There is no high speed adjustment on this carb. The spraybar looks like an ST spraybar.

Probably the servo gives the adjustment for high speed. Not sure what that screw is on the end, just to hold it on? However it is, you can check by blowing in the nipple and seeing where the flow slows down. That is where the arm should start at probably.

Ok. For now, I fitted an Enya. Carb.

I put a different throttle on this MDS diesel since I suspect there are parts missing or
broken in the OEM carb. I also swapped out the slotted screws for socket heat screws. I’ll probably need to seal around the contra assembly and the cooling jacket, beneath the head screws, and I’ll need to find a wraparound type exhaust for it. Otherwise I think it’ll run. Not sure how well - the piston fit isn’t so great, but perhaps a little running will fix that.