Calvinman

Hello Again,

I purchased a lot of 10 glow engines and one of them is a MDS 48. I have read a few posts on them and was wondering how one can tell what carb is on it. I am not sure what the difference is between the two carbs either, is one more prone to an air leak than the other, or are there other differences. My instruction manual for the engine calls the carb an aeromix carb.

I have also read that this engine is happier with low nitro fuel. I also have a RJL(I think that is the initials) can anyone tell me if this engine runs better on low glow also?

Is there a macs muffler that will fit this motor, the stock muffler is like a chunk lead?

Thanks again,
Calvi

j.duncker

My Feedback: (2)

That looks like an early one to me. Yes they have issues with air leaks at the carb to crankcase joint. A little silicone fixes this. Also check for an O ring on the needle.

I have had several MDS engines including a 48 and all took some running in before they would throttle well. I am talking about an hour or more. But once that was done and I had the bottom end dialed in on the carb I never touched the needle other than for a significant change in the weather. Two or three clicks richer in winter.

N.B. Mine did not like high nitro fuels. 10% max and I used 5% all year round.

There are the odd total MDS dogs but mine were all very good engines.

Calvinman

Hi j.duncker,

Thanks for the info, I gave this engine a short bench run on 15% and it ran and started fine, I will pick up some 5% and run it in for an hour. It has an O ring on the needle valve, I will check out the carb to crank O ring and use a little silicone as you suggest.

Calvi

j.duncker

My Feedback: (2)

If you have problems with inconsistence needle settings fit a new O ring. The OS one fits.

Gray Beard

My Feedback: (-1)

MDS, Many Dead Sticks. The Russians never did figure out how to build a carb and there casting was a real problem. The engines didn't last long in the states, Horizon quit importing them. I had pretty good luck with the .68 but not so much with there .58s. They run better with FAI fuel but 5% will do it. Very high compression engines. Every time I got a .58 broken in and running right the case would break at the port. When they run they are pretty good engines. At one point Horizon offered a replacement carb for free but it didn't work any better then the original. If you give Horizon a call maybe they can answer any questions you have on parts numbers?

Calvinman

MDS 48 update,

I have a gallon of 5% nitro and a mac's muffler(for the OS 55 AX) the muffler is 30% of the weight of the stock muffler. I have read in other threads that the stock muffler is prone to break so hopefully the lighter muffler will negate this? I will be running her in on the weekend, hopefully I will get the hole gallon through it and I will be able to tune it to be a consistant running motor.

Calvi.

Calvinman

Running it in,

I am getting head temperatures in the 115 deg celcius range. Not too reliable yet, but slowley getting it dialed in. I tried to remove the carb last night to put a little sealant on the "O" ring but it was stuck to tight I was thinking the previous owner had already done this(it looks like the motor was run for only a few minutes or a tankfull before I got it).

I am now thinking the carb is leaking because at 1/3 throttle it seems maxed out and will die at any higher throttle settings.

Calvi

Calvinman

Second day of running it in,

Well I only put about 3 tanks through it yesterday so today I took a different approach. I am now starting the motor at full throttle, I hate doing this but it is working much better with runs up to 2 minutes now and I can throttle it back to idle now, idle it for 20 seconds or so and ramp it back up to full throttle with only the occasional cut out. The needle valve is open around 2 turns.

I changed out the O ring but it looked to be ok, my mistake was to set the carb so It would start at an idle.

Calvi

Gizmo-RCU

My Feedback: (27)

Horizon got rid of these engines for a good reason. I had a 58 that ran well when it ran but never could get it really reliable. It made several trips back to Horizon for new carbs and but never ran right. In discussing the problems with their Tech guy
he said they had a pile of them, all problem engines. He was totally fed-up, shortly after that they discontinued MDS.
Were it me I would not put much effort into your engine.........

aspeed

There is probably just an air leak at every possible joint. It would be fixable if you have the time and patience along with a dab of silicone at every joint, nut , and gap. Once you find the leak, share the results. I have had fair results with my smaller MDS stuff. One is a strong and reliable runner, one likely is but haven't got it in a plane yet, and one is hard to start, but runs ok. Two leak out of the front case way more than I think they should. I always start and run my motors at full throttle. I guess it is a control line thing, but I also think it is supposed to break in at the rpm's you will be flying at, just a bit richer.

Calvinman

Hi guys,

Well the engine is running like a top right now (touch wood) and will start with the chicken stick at idle and go to WOT and run for 2 and 1/2 minutes, then idle for a minute then back to full throttle with no problems. I am still running it very rich on the top end and a little rich on the bottom end but the muffler pressure line popped of while I was at full throttle and it sure sounded good as it went to a lean setting before dying.

I now have 3/4 of a gallon through it but I have read that I should put a few gallons through it before leaning it up. Yes I am just killing time with this engine while waiting for spring to come around so I can go flying If it turns out to be a consistant runner then I will put it on my next project.

Calvi.