jim69rcr

I have a Russian MDS 61 engine that I bought at a swap meet. The engine appears to be little used / excellant conditon with great compression. I presently have it on a test mount, mounted inverted, with a zinger 11-6 prop running Sig 15% nitro fuel ( 20% oil, 1/2 synthetic and 1/2 castor ). I'm having trouble with it tending to suddenly lose RPMs when moving from moderate throttle toward full throttle -- it may suddenly stall or recover when I pull back toward a lower throttle setting. Sometimes it will run near full throttle for a time and then may start to lose RPMs.

Also: I presently have a spinner and am starting with an electric starter but the other day I had it mounted upright and it easly started by hand but I noted it would sometimes run backwards -- is that the nature of this engine ? Previous I'd only found this on .049 reed valve engines -- but I don't have experience with larger engines. In the upright position I noted the same throttle problem mentioned above.

Any advice would be appreciated. Jim

downunder

MDS engines tend to have quite a high compression so give it a try with 5% or less nitro and retune. Running in reverse when hand starting is just a sign of slight overpriming (the brute force of an electric starter hides this).

aussiesteve

Check your carb mounting o'ring then fiddle with the needle settings.
I had the sam problem on a couple of MDS 48's. The carb o'ring was badly deformed and it was pretty sensitive on the low speed needle. After fiddling with the tuning, thet became pretty good runners.

Turk1

Jim that recovering when back throttle signs lean low end needle.Try to open slightly your low end needle until complaints finished.That means when vacuum reduces after your carb barrel opening,fuel flow also reduces instead of more.

Eagle Flyer

My Feedback: (84)

A lot of glow engines have a built in design flaw. They put an oring around the carb neck.You can still see it after the carb is installed. Fine. That seals the carb at that point. But there is still an air leak around the clamping bolt below it. I fixed an MDS by simply putting another oring down in the "manifold" so the bottom of the carb seals to it. That being the case eliminate the top one so to be sure that the carb goes down into the manifold far enough to seal the carb to the engine. A lot of engine companys have this flaw. Is it a problem? That depends upon how the clamping bolt seals or doesn't seal when it is tightened up. But it worked on mine. It won't work on engines that have no ridge inside the manifold to support the oring or on ones that the oring isn't held up high enough for the carb to contact it. Perhaps more than one oring is needed then. You should be able to tell by how it feels when you push down on the carb. If it feels rock solid then you aren't sealing up to the oring. If you feel just a slight amount of "give" then you are up against the oring and it will be sealed. Also read up on the other suggestions here. I did get mine to run on 15% nitro but I had to let it warm up completely before it would transition with out dying. And it was picky about heat range on the plug. But I can't recall what I used. But it had to be absoluetly up to temp or it would not run other than at an idle. But then it screamed!!! And that was with the old style carb.

jim69rcr

Thank you gentlemen, for your suggestions. The local hobby shop carries 10 percent nitro but not 5 percent. Perhaps they could order it -- but I hesitate try that until I've investigated per the other suggestions. Hopefully I can eventually reply on what works for me.

Anyone else that has experience with this engines: Your input will be greatly welcome.

Jim H.

Julian537

My Feedback: (9)

run 5% nitro

DarZeelon

Jim,


If not, change your hobby shop, or mix some 20/80 fuel, with good quality castor oil (Sig/Baker's AA, Klotz BeNOL, or Morgan CleanCastor). This engine is designed to run with low-to-no nitro and with 20% total oil. Sig Champion is a good fuel.

fiery

My Feedback: (2)

MDS ...

I sometimes wonder how many of these engines were bad mouthed and then junked by exasperated owners due to inappropriate / low grade commercial fuel.

I saw a 1st generation MDS 40 run over 10 years ago. It went fine - on good old 80/20 (castor) (no nitro) fuel and a simple warm rated (not hot) plug. Oh, and careful attention to carby settings.

"Must Destruct Soon"? "Many Dead Sticks"? OK, some (maybe many) early MDS's had carb issues (not unsolveable) ... but these engines were better than many believed.

Nitro creates problems with some engines. Many neophytes do not understand this.

I continue to enjoy superb reliable performance from my MVVS .49 (circa 1998) and it has never seen a drop of nitro ... 80/20 all the way (self mixed), and at least 1/2 of the lube component is castor ....

fiery

PS. Are MDS out of the engine manufacturing business, or are they simply no longer distributed in the US? I would be interested in acquiring a 2.14 new ... or NIB.

Sport_Pilot

.

It is likely you biggest problem. I suggest that you do a yellow page search for VP Racing Fuels, or if not found a web search for VP Racing Fuels and buy some methanol and castor oil. Just mix 20% oil to 80% methanol. The engine should run fine on that. You could always mix this with 10% nitro if you really needed 5% nitro.

jim69rcr

fiery

Google "russian MDS engine" or try carlsonengineimports.net ( the first search hit ) -- they list these engines for sale.

Because of the multiple comments about fuel I think I try to come up with some low/no nitro.

Jim H.

fiery

My Feedback: (2)

Here's the link ...

http://mds-engines.ru/eng/index.shtml

But ... I don't think anyone is at home [&o]

I see Sussex Model Centre in th UK is having a sale on their last MDS .48's ... 7 units left.

http://www.sussex-model-centre.co.uk...d.asp?id=20975

Sounds like they are not expecting to receive any more though.

fiery

rinkhals01

I just put another head washer in and it sorted the nitro issue out......we as modellers always tend to go the difficult route first, whereas simplicity is actually the best answer...LOL. I have heard more arguments and debates over which fuel , nitro content and what type of lubrication is the best to use in a $70 nitro engine, and this is from modellers who do not give a one second thought as to what fuel to use in their $50 000 motor vehicle engines...ha ha ha

Sport_Pilot

15% nitro in an MDS? You are lucky the piston and head is in one piece! Use FAI fuel only.

tiffitech

Maybe you are interested in this thread: http://www.rcuniverse.com/forum/m_10..._1/key_/tm.htm ?

Regards,

Holm