megatech m46 engine problems
 

Hello,
On rebuilding my plane after a minor crash my engine stops suddendly during idling and when i lift the nose by 45 degrees the engine quits again. And after a 3 minute test run, the area on the wing right behind the engine was covered with oil.
Secondly the M46 dosen't have detailed instruction on their engine and i just found a black needle and that's the fuel-air mixture needle but I didn't find any hi-speed or low-speed needles. Can anyone help me..
Thanx.

megatech m46 engine problems
 

Since you mention a minor crash, it's possible that the klunk in your tank is stuck at the front, and therefore isn't drawing fuel correctly. That's my first guess.

Other possibilities include holes in the fuel line, or other air leaks in the tank/fuel system.

The needle valve you found is the high-speed needle.

I'm not sure about the carb on the Megatech .46, it might have a second needle or low speed, or it might be an "air bleed" carb. I know the Megatech .15 uses an airbleed. Does your carb have a really small hole in the front of the carb, and a small screw that partly covers it? If so, that's an air bleed carb. That screw is your low speed mixture setting. Check to make sure that hole doesn't have any thing in there blocking it.

If the carb doesn't have an air bleed on the front of it, then it's likely a two-needle design, and the low speed needle is usually that little screw in the center of the thottle arm.

The important thing about low speed mixture, weither air bleed or two-needle, is that it doesn't affect the full thottle running (much). So, if you are having the problem with the engine dieing when you tilt up the nose, it's not the low speed setting.

As a general thing after a crash, you should check carefully for any junk getting in the carb.

megatech m46 engine problems
 

do i have to open up the carb and clean it ?

megatech m46 engine problems
 

I wouldn't until you've ruled out other problems.

I don't know how you crashed, but you should at least look down the venturi opening and see if there is any crud in there. If there is, get it out. If it's nice and clean inside, you're more likely to be ok.

megatech m46 engine problems
 

the washer between the needle valve and carb is a little chipped on the side.. so i guess replacing that first would be a good idea

thanx for your help

megatech m46 engine problems
 

yeah i figured.. anyways i found the idle speed screw and i changed it a lot .. so right now both my high speed and idle speed needles are messed up..
the engine starts only when i apply full throttle and it's really fast and if i reduce the throttle to 1/2 the engine quits.. also there is a lot of white smoke coming out.

PS: I also tried changing the propeller to a broken one that i had before so that it'll make it safer for me to work with the engine. It is ALMOST balanced and really short. Does that make a difference other than the increased vibrating due to it being unbalanced?

megatech m46 engine problems
 

Vegassky,

I would not start buying new parts yet. It sound like the engine is running to rich on the low end. I have a Megatech .15 and it is a great little engine. Since you said that both of your needles are messed up right now, I can only assume that you do not have much experience tuning engines. The best way to get that thing tuned is to find someone at the field to adjust the needles. If you can not then follow these simple rules.

Start with the engine running at high throttle, tune it to get max RPM then back the needle out two clicks.

Move the throttle to the low throttle. If the engine revs up and then dies, then it is to lean. If the engine bogs down and then dies, then it is to rich.

If the carb has a small hole in the front, then moving the needle in, is adding more fuel. If no hole in the front, then moving the needle in is less fuel and moving it out is adding fuel.

I sure hope this helps you out.

Bob

megatech m46 engine problems
 

Whoa, NEVER RUN A DAMAGED PROP!!

Even if the prop appears to be "balance" statically, it won't be aerodynamically, and will vibrate like crazy.

It might also be weak, and throw a blade.

If it's "shorter" as you said, it might not load the engine enough, and you will get bad engine runs (over speeding), or even damage the engine, if it's too small.

Please, get a new prop.

Ok, safety aside, see if you can find in the manual if they say how to reset the needles (both) to factory settings. Most low-speed screws don't need much changing. And they are VERY SENSITIVE. Make changes 1/4 to 1/8th of a turn at a time, very very small movements.

If it runs full throttle, and puts out a lot of smoke, you are likely rich on the high end, that's good for now.

As you reduce throttle, if the engine stops suddenly, your low speed is too lean. If it slowly "winds down" and then stops, or you see liquid coming out of the muffler as it's slowing down, then it's too rich.

Your best bet is going to be to find someone near you that can help in person, trouble shooting engines on line is really really hard, more guesswork than anything.

I agree that I doubt that chip on the outside of the washer is hurting anything. You should see the dents on the casing and cooling fins on some of my engines.

megatech m46 engine problems
 

i had a feeling that the decreased weight and inertial torque provided by the propeller has gone so that's why the engine quits at half throttle.
will replace it will the new propeller and try adjusting the low speed needle.

M46
 

The Megatech M46 is the same as a Mecoa 46. Go to

http://www.mecoa.com/mecoa/guide.htm


For the details. It is a twin needle carb but the low speed needle is adjusted with a Small flat blade (jewlers). It is recesed on the side where the throttle arm is.

Oily in Germantown
Francis

megatech m46 engine problems
 

thanx for the page.
Just releaized oil dripping down the front landing gear. don't know where the leak is at coz i don't think there is any way to pull the fuel tank out unless I cut out all the wood in between..

megatech m46 engine problems
 

Is it oil or fuel? If it's oil, it's coming from the exhaust end of things, the source could be a loose muffler or a loose muffler tail cone, both are common problems that get oil all over the place.

megatech m46 engine problems
 

well ok here is my deduction.
I filled in the tank full yesterday morning. by after it was half full (i did not run the engine after fueling it). and today it's very little below half full. So I think it's the tank cap that is fitting tightly over the tank. Any suggestions how to replace that ?

megatech m46 engine problems
 

You shouldn't leave fuel in your airplane's tank over night. The vent line to the muffler is open to the air, and over time, the fuel will absorb water though there. The carb line is also open to the air, but the needle valve restricts it down a bit. You can also get fuel syphoning out of the tank and in to the engine or muffler during handling, making a real mess. (I once syphoned a nearly full 6oz tank down to empty while attempting a repair on the plane).

That said, if you think the tank stopper is leaking fuel, how to fix it depends on the tank. If it's one of the style with a screw that goes thought he middle of the stopper, try tighening the screw. You can also sometimes seal up a tank with GOOP brand glue.

Either way, it sounds like you should remove the tank from the plane and do a pressure test to see if it's leaking somewhere.

megatech m46 engine problems
 

If you filled the tank and left it for a day, with the plane sitting level, only to find the tank half empty, then I'd say you messed up the tank when you crashed. (Assuming that your engine is mounted upright. If inverted the tank could drain through the carb.)

It sounds as though the tank only drained about half way, which suggests a few possiblities: either the tank has a split about half way down, or the stopper was dislodged, or one or more lines are leaking where they enter the tank.

No matter how you look at it, you're going to have to pull the tank. It SHOULD be removable without cutting any wood, but I don't know what the plane is.

By the way, a bad fuel line could very well be causing the problems with your engine.
Dennis-

megatech m46 engine problems
 

The tank can also empty to "half" though a syphon in to the carb. The tank will empty until the fuel level in the carb matches the spray bar.

Still, DBCherry is likely right, and you should take out the tank and inspect it, espeically because you are having engine run troubles.

megatech m46 engine problems
 

Thanx for your help guys but it's a nitro airstrke and there is no way the tank is coming out without a saw !

megatech m46 engine problems
 

Not that I doubt you, but I've never seen that unless the engine was inverted. (But I never let my palnes sit overnight with fuel in the tank either. ;) ) That's too bad because I doubt you'll solve your problem without removing it. :(
Dennis-