rc airplane nut

My Feedback: (5)

I have an MDS .48 engine in my Ultra Stick and its been running really badly. Several people have tried working on it but no good[&o]. It runs good level but when I hold it up it either looses RPMs or just plain quits and when flying inverted it looses RPMs. So, I've been planning on getting a new engine for it and since I live at high altitude (and want to take some lead off the noze) I was thinking about a .60 size engine. First question- how much does an MDS .48 with a Tower Hobbies muffler probably weigh (the reason is because I want something at least 3 oz. heavier)? Question #2- Would an O.S. 65LA [link=http://www3.towerhobbies.com/cgi-bin/wti001p?&I=LXPUE1&P=SM]link[/link] be very good for it? Question #3- what size prop would be best for it?

rc airplane nut

My Feedback: (5)

Question #4- would this be a very god idea? If there is any engine that you think is better than please tell me. Also it can't be very expensive. By the way, incase you think its a crazy idea: I wasn't the one that came up with it.

andrew66

Sounds like it is going lean. If richening it doesnt work, then take the high speed needle off and flush fuel through the carb, in case there is some crap in it. Also, is the tank set up properly. If its too low or too far back, it will cause it to be a b**** to tune. Another thing, check and replace (if needed or suspected) any fuel line.
Also, sometimes the O ring for the carb will be damaged. Check that out too. (and the bolt that holds the carb in)
Always try EVERYTHING before buying new.

rc airplane nut

My Feedback: (5)

I have tried some of that and I will try the rest. Also if it still dosen't work, is the .61 four stroke made by ASP that hobby city sells, a good engine?

jester_s1

Most guys have had good luck with ASP, but it does have its haters. The brands that rarely cause trouble are OS and Thunder Tiger. Evolution and Magnum seem to have good reputations these days, although older ones didn't so much.
The .60 LA won't make as much power as a ball bearing engine. You probably won't be happy with it.

To fix your MDS, it sounds like you have a fuel supply/pressure problem. Here's a rundown of stuff I would check:

Running muffler pressure? Is the line clean?
Fuel filter clean? (you are using a filter, right?)
Holes in any lines or leak in tank?
Fuel line pinched or kinked at all?
Tank mounted near the engine without excessive fuel line length?
Correct type of fuel line in use?
Clunk moving freely near but not touching the back of the tank?
Clean carb (as already suggested)
HSN tuned 300-500 rpm rich off peak RPM?
LSN tuned so as not to load up and to allow good transition?
Carb o-ring, rear plate and head sealed airtight?

paysonhobbies

My Feedback: (2)

You probably would not like the 60 on the 40 size airplane. I tried that once and even though the 60 made more power in the end the 40 flew the airplane better. You should look into getting a used 46 fx for it.

beau0090_99

One other thing to check is whether the tank is holding pressure. If you can get the tank out of the plane, put under water and blow into one of the lines while the other one or two are plugged and look for bubbles.

Also, ASP engines, I believe, are the same as Magnum. I would buy another Magnum XLS-46 in a heart beat. I cannot get over how much power mine has. It took a little to break in and get the low end tuned, but now is rock solid and very hot.
Good Luck,
Curtis

blvdbuzzard

The Magnum .46 is a sweet running engine and would fly the plane. A Magnum .52 would make it way over powered. They are a little hard to get but a K&B .48 would rip the wings off the plane.

What fuel are you running in the MDS? the ones I have touched liked very low nitro. 5% nitro worked very well. We ran 5% heli fuel. the MDS line had lots of air leaks and needed to be sealed up. They did like large props. Sort of like a 4S, load them up and use the torque of the engine.



Dru.

rc airplane nut

My Feedback: (5)

Thanks. I'm going to the field tomarow and I will ask for help with those things.

Gray Beard

My Feedback: (-1)

So, your the other guy that got stuck with an MDS engine. Sorry, I can't help myself, I think I still have four of them under the bench that I use for parts. There was a reason Horizon quit selling them. Many Dead Sticks!!
So far the best replacement I have found for the .46 range of engines is the O.S. .55AX, it is a pretty good engine for most planes of the 40 to 60 size of ARFs as long as you don't care about 3-D flying. Not up to flying a 60 size kit built plane though due to the added weight of a kit build. Also not a cheap engine.

andrew66

If you need to replace the engine, get a Webra or GMS. The Webra in my opinion is the best all around engine made. The GMS is a close second, cause it is cheaper. A little heavy compared to the Webra. And I dont know if they last quite as long.

jimmyjames213

My Feedback: (2)

i second the gms idea. the gms.47 is a great engine that is very reliable, mine will 1 flip start. turns a 10x7 in the 14600 range on 10% nitro
i also second the magnum 52 idea, mine is still new but it runs like a top turns the same prop at the same speed as a gms.47 on its frist tank of fuel. it will be hauling butt in a few gallons

andrew66

I got my GMS with a plane i bought. It usually started the first flip (ran backwards alot) The guy who had it, didnt use after run oil, and caused the bearings to fail. Before i had this, I always thought they were just another cheap engine. If I had taken the engine apart and cleaned it, I bet it would have gave me years of trouble free service.

rc airplane nut

My Feedback: (5)

I thought the same thing.