MDS 1.48 needle settings
 

I have a brand new MDS 1.48 that I have just run 5 tanks of 5% fuel through. Not a single problem on the ground, does not stop until I kill it, idles at 1800 RPM every thing worket flawlessly until I got it in the air for the first time yesterday. Then, DEAD STICK!!!!!! The only thing I failed to do was check the engine performance on the ground with the plane at a 45 degree angle or more. Could it be too lean? Please help! Thanks.

RE: MDS 1.48 needle settings
 

Richen it a full 1/4 turn to start with. There's nothing wrong with running these big 2-strokes rich for the first 1 or 2 gallons. It is a little messy on clean-up, but the motor will run a whole lot longer for you. When you re-set the needle do the vertical test at 1/2 or full throttle, it shouldn't bog at all, it should try to fly right out of your hands. Please be careful on this test, I know I don't have to tell you this, but I always try to cover my bases.

Good Luck,

Ken

RE: MDS 1.48 needle settings
 

Thanks Ken I will try that today. I forgot to add in my post that after the five tanks of fuel, I leaned it in to see where it's max was and it reached 9200 RPM, I then richened it to 8500 which was where I left it when I flew it. I guess that was too lean huh?

Charles

RE: MDS 1.48 needle settings
 

No way to tell until you fly it. The vertical test well give you a great heads up, though.

Let me know how it works for you.

Ken

RE: MDS 1.48 needle settings
 

If you are using an aftermarket pitts muffler with large exhaust outlets the muffler pressure is low and it makes the needle settings creep a lot. There are two fixes. I'm running a Perry regulating pump using the bypass system. ("T" fitting at the carb returning excess fuel to the tank) You can also restrict the muffler outlets some to increase pressure.
Also, be damn sure you aren't getting air leaks at the carb. The mds retaining bolt is very close to the crank and has very little sealing area. The new C2 carbs have a longer throat that engages the casting near the crank. I was told that the lower O-ring was not needed with this new design, just the on at the top of the neck. Not true! It would air leak around the carb retaining bolt when the engine heated up and the crankcase expands. I would group most "runs great on ground, dies in air" to this leak.
I'm running a lower and upper o-ring. Some use sensor safe RTV to accomplish the same.
Its a hard leak to diagnose, the way the carb and crankcase heat and cool it rarely shows up on the ground. I only found the retaining bolt leak while doing some perfomance testing on a test stand and then ONLY after a particularly hot run.

If you seal up the carb, run low nitro fuel, and get good muffler pressure or a pump, the MDS runs great.

RE: MDS 1.48 needle settings
 

I had a 148..the best way to adjust the needle is place the engine just behind the rear wheel of a nice pick up truck. Put the truck in reverse and nail the throttle, then put in drive, floor it again. Repeat as necessary until the stress and frustration is gone. (could be doing this a while, so be forwarned)
When you start enjoying yourself and catch yourself smiling uncontrollably, stop and get out, pick up offending engine, and toss in nearest trash recepticle.
Worked for me, your results may vary.

OK, the other fix is buy a ASP 108 carb, install and fly. Price is about 35 bucks.
Problem solved. The best thing you can do with the stock carb is drill a hole in it and put it on a key chain...no foolin' mine is still on my key chain after a couple of years.
Great conversation starter.
True story, no foolin', fact Jack.
The 148 is a stump puller when running right, but usually kills your favorite plane because of Many Dead Sticks.
FWIW, I was determined to get every MDS running perfectly..I took it personal and eventualy owned 8 MDS's...sold everyone except 2 68's....which I'll be selling this fall with all my other glow.
Good luck.

RE: MDS 1.48 needle settings
 

Where do you get an ASP 108 carb ?

RE: MDS 1.48 needle settings
 

Mike, my MDS came with the new C2 carb so, from what I've heard, it should work fine and not give me any problems.

RE: MDS 1.48 needle settings
 

Horizon has the ASP 108 carbs..they even gave them away for a time as a direct replacement for the stock carbs.
And FWIW, 99% of all MDS problems were carb related, air leaks the most probrable.

RE: MDS 1.48 needle settings
 

Looks like all I had to do was richen up the HSNV a little. Thanks for all your help guys. WOW, these big glow engines really use a lot of fuel! How many tanks of fuel do you think it will take until the 1.48 is pretty much broken in? What plugs are you guys using for these large engines (when I finally need fresh plugs)? Thanks

RE: MDS 1.48 needle settings
 

I do my best not to steer you wrong. I'm glad its running good for you. After about the first 1/2 gallon you can start to lean it a couple of clicks or so if you want. I usually run about a gallon through before I start leaning the needle. It takes a while for the 1.48 to break in, but when it does it'll pull you around with the plane if your not careful!!:D:D

Gotta' luv' the big ones!!!

I usually replace the plugs in all of my 2-strokes with OS #8's. A great all around plug.

Have fun,

Ken

RE: MDS 1.48 needle settings
 

On running in mine, took about three gallons of caster. The first thing to know is the slow running needle is very sensitive adjust about 1/32 of a turn at a time. The second thing is that the the 2 needles seem to be interdependent at about 50% throttle. As my funfly [ Pete Tindal Excitation ] has unlimited vertical with the 148 I run about 3 clicks rich on the main needle then adjust the slow running needle for a clean pickup. I then pull into a hang. It it cuts I can usually catch it by pumping the throttle stick in level flight. I then land and unscrew the slow running 1/32 and try again. Once it is set do not fiddle with the main needle if you do then you may need to adjust the slow running. I just turn up flick and Fly/Fly/Fly. I think I had one dead stick this year. My set up is temperature sensitive. About 2 clicks and 1/16 richer when it gets lots colder. I now use 5% nitro 18% synthetic 2% caster. Best prop by far APC 18x6 WIDE BLADE. I have run 20/30 gallons through it now and it is still good.

Most people who knock MDS engines either don't have one or if they do/did they didn't run it in or don't treat the slow running sensitively. [ THIS SHOULD START SOME FLAMES ! ]

John Duncker

RE: MDS 1.48 needle settings
 

No flames from this direction.

You are right on with your set-up style. When I said I start to lean it a little, after about a gallon, I mean a little, one or two clicks.

Once any of my engines are set, I don't mess with them, unless we get a major temperature or humidity change.

Otherwise, I like to fly, not play with my motor all day.

MDS is a great motor. if you know how to use it.

Ken

RE: MDS 1.48 needle settings
 

I agree as well fellas! This is my first MDS and I think it is a powerhouse. It idles at 1800 all day long with a 16x6 pro zinger wood. As a matter of fact I burned a half tank of fuel just at idle(it took about 35 min.) and all I use is 5%. I will probably start looking for a 2.18 next.:D