Hi,
I've just completed my first IC model and cannot get the engine (MDS 40) to fire up. The engine has fired up in the past but since then I have trield everything to no avail. I have removed the cylinder head to ensured that ther is no fuel still in there and confirm that the piston is moving freely, and checked that the glowplug is still heating ok. The problem is when I try to start it, it won't start without an electric starter, and when an electric starter is used it just spits the fuel out the carb, again without starting the engine. I am tending to think that the carb is blocked but are unsure how to clear it. If anyone has any other ideas or advice on clearing the carb it would be much appreciated.

Many Thanks

Al

I doubt the carb is blocked since you have fuel "spitting" out the carb. It should start.

I would try ALL of the following at once:

1. Use a NEW container of fuel. The fuel may be bad.

2. Install a NEW OS #8 glow plug. Just because the plug lights up does not mean it is good.

3. Make sure your fuel and muffler pressure lines are not reversed either on the engine OR at the tank. Don't ask me how I know about this one.

Frow what I have read here, MDS engines require a LOOOONG break in, and even then, the general concensous is they are best used as a Metal Door Stop.

When you get tired of messing with that engine, I suggest an OS FX/AX, Thunder Tiger Pro or Evolution engine for your 2 strokes and a Saito if you want to go with a 4 stroke. I have NEVER had a problem with any these engines that steps 1 - 3 hasn't solved.

I agree with the above posting. go for a short drive, find a lake or river, and give that piece of junk a good heave- ho! Then get yourself a good engine. The above suggestions were all fine; my preference for sport flying is the thunder tiger, because it is cheap, it is VERY reliable, and you can basically take it out of the box, strap it onto your plane, and after running about a tank full of fuel through it on a run up stand, you can break them in in the air. I have had these engines start on the first flip right out of the box.

No reason to pitch the engine. Get some help. MDS engines are fine. Follow the hints above, make sure your needle is not set too rich, and make sure the fuel is good. Put a good plug in it and make sure it isn't flooded. Sounds like you have way too much fuel in it if it is spitting out the carb.

Are you using a starter or flipping it? If you don't have a started, it won't be easy to start it.

I would also check out the hoses making sure that they are connected to the proper places and that they do not have a hole in them or a crack anywhere. Replace if any doubts exist. Is tank located properly elevation wise, center of tank at level of carb inlet. Don't be put off by comments on the MDS, they are powerful and reliable engines when adjusted. Look at your owners manual and be sure your needle valves are at recommended settings. You could experiment with opening each on their own and see if that makes a difference. The low speed needle may be set incorrectly. I have 4 OS engines and they have their problems just like any other engine. OS had serious problems with the cylinder linings peeling. believe me I know. I also have Tower and MDS engines and they are great performers too. Find an experienced flyer to give you some suggestions, you will find the problem.

Troublesome MDS engines like an idle bar plug. OS #8 plugs are great but the MDS needs the idle bar. The MDS 40 likes to rev so use a 9x6 rather than the usual 10x6 at least while attempting to get it to run dependably.

This engine is known to be troublesome and difficult. If you are new to engines put it on the back of your shelf and go buy one of the other engines. You can go back to the MDS at a later date when you have more experience and time to fool with it. Some of these MDSs come out of the factory perfect and others can cause hair pulling. If as you posted you removed the cylinder head to verify there was no excess of fuel there and the piston was moving you most likely should give up on it now and save yourself much aggravation.

If, and only if, you have good talents with engines look up the MDS threads about what others have done. There is a very misleading page over at JustEngines stating the carb is the problem and spitting from the carb tends to make people think it is the carb but those of us who have gotten a bad engine to run well know better. Also you will note that one of the guys substituted a known good Supertiger carb and the symptoms remained the same.
http://www.rcuniverse.com/forum/m_20..._1/key_/tm.htm
http://www.rcuniverse.com/forum/m_23..._1/key_/tm.htm

Welcome to the forum.

80 bucks and about 15 minutes will get you flying- why go through all of the frustration to get that MDS abortion running right? Don't you want to fly?? Get a reliable, new engine out of the box, take it to the field and have someone help you start it. You'll be flying in no time. Why spend hours and hours on that engine? I am assuming your time is important to you. I have OS, Thunder tiger, Enya and a few others, and if an engine of mine goes sour on me, I spend a little time on it, but not hours and hours! You can learn about engine tuning as you go- you need to get FLYING son!

Fuel spitting back out of carb. is cause by back presure from muffler or a sleeve that has turned. It also may have leak in crankcase loose screws incrank case. And last cranking engine the wrong way will cause fuel to blow out of carb!

[8D]

If it is not firing on the prime I would suspect the glow plug. if that is the problem the plug will be wet after trying. If it fires on the prime then quits, it is probably a fuel issue. that is too lean or pluged or backwards or the mystery ghost.

I have an MDS 40 that was giving me problems at the beginning too. Problems include: not starting, fuel spitting out carb, runs at idle but not at full throttle, and many others quirks.

What I did to get it running (still not quite broken in yet), were the following:
- 0% nitro
- idle bar plug, the Fox Idle bar plug is cheap and works great with this engine
- adjust the low end first (most people don't recommend this, but for some reason it helped my engine) for a reliable idle, since I couldn't get it to run past 1/2 throttle at first. Once the idle was reliable, I ran it at 1/2 throttle and below for 2 tanks. After this, I adjusted the high end and it is running fine now.
- 9x6 APC prop. I started with a 10x6 and it wouldn't run reliably. Once the 9x6 went on, it ran great.

I'm still running it on the bench (about 6 tanks through it now), and will continue to do this for another 4 tanks before I install this engine in a SPAD.

Good luck.

Fly NB

Hi,

I think you may have discovered the cure for dead stick episodes if you can't start it. MDS = Multiple Dead Sticks.

Seriously if you work on the process of elimination. Change one thing at a time. If you have fuel, compression and a functioning glow plug it must at least fire. Check for seals/leaks and that it isn' too rich!

I have actually seen the things run in QM 500 pylon racers...........but I wouldn't own one.

Cheers,

Colin

Ive never had fuel spit out of my carbs unless I plugged the muffler. Maybe your too rich?

John

Make sure the muffler is not stopped up. Maybe a dirt dobber's nest or something.

I am not saying this is your problem, but it sure sounds like it. Since you didn't say how long the engine ran the last time, I just thought I would throw this in for you to check. The symptoms you describe is exactly what this guy had.

http://www.rcuniverse.com/forum/m_22...tm.htm#2289044

thanks for all your help, I finally got the engine to fire briefly then cut out so I'm at least making progress. All it needed was a little fuel in the glowplug hole, but it sounds like its leaking pressure somewhere so back to finding out where from and i'll take it from there.

al860, I'm pleading with you. Please give up on this one and go get an engine that runs. Removing the plug to prime an engine isn't the way to do it and your doing so indicates you need more experience before tackling this engine. I have been doing engines since the mid 50's and it took me most of the last season to get mine to run. You will only frustrate yourself by continuing.

That said, You can disregard all posts by persons that do not have an MDS 40. They are well meaning but just don't understand the gravity of the problem. You can disregard all posts recommending changes to nitro. When the engine is fixed it will run on any nitro level as proven by empirical results. You can go to Dub Jett's web site and use the procedure he has for setting the carb. It will work on the MDS. Because you have not yet reset the bearings on the crank you can only get these engines to run in a very narrow range of settings and the low setting is exceedingly important. These engines go from not running lean to not running rich in a quarter turn or less so the low end has to be smack on. My experience was that after the bearings are reset it behaves just like all other engines and is easy to set up.

Please, go buy an OS or Thunder Tiger your nerves will thank you.

I think I will give up on it at the moment and get another engine, but because its bugging me by not working I will plod on with it until I get it working or totally strip it down and knacker it completely. Thankyou everyone for all the help as it has helped me understand the workings of the engine better and I will eventually get it sorted.

Al

Al, if you had the head off, you should pull the muffler and check the cylinder orientation as someone suggested above. Set the lowspeed needle about 1/16 inch from the end of the spraybar, I have about 12 MDS engines now and they are not a problem. The idlebar plug is good advice, low nitro and lube 20% a necessity Try a heavier prop load, they are easier to set up with a 10x7 or 11x5. When a guy uses a childish anacronym for MDS that tells me he's never owned one. If you lived in the States I'd have you ship your engine to me and I'd spend about three minutes getting it running.

Come on hobbsy, open that offer up a bit. Just because he is in the UK you limit the offer? How about he agrees to pay the shipping both ways?

( The jaws of the trap open. Will hobbsy step in? )

I already have stepped up and so far have avoided stepping in it.

hobbsy,
Maybe the best thing we can do here on the beginners forum is tell them when not to step into it.

I can imagine the frustration a person new to the sport would experience trying all the various plug and fuel combinations on this engine. What a waste of time, money, and a major bruising to the ego when it still won't run well.

Incidently, a troublesome MDS 40 needs a smaller prop not a larger. They just flat out won't run on a larger one. Been there, done that.

Yes, all your MDSs run fine but there is a batch of stinkers out there which you have not had the misfortune to own. I think it would be great if someone sent you one to play with.

They have and I have bought several troublesome ones that never are.

thanks again for all your help guys, i've now got an engine that starts ok but needs fine tuning so its off to play with the carb settings.