Faisalk, - what about your Thunder Tiger.......Same problem?
 

I believe you said you have both makes. - OS and TT.

I have two trainers...a Telemaster 40 w/ an OS 46FX, and an Eagle 2 with a Thunder Tiger Pro 36.
The Thunder tiger is used (Ebay) and fortunately it runs like a Swiss watch, starts with a hand flip. Great engine.(bought a used TT Pro 46 too).

I have been breaking in the OS 46FX since early spring with 5%, and didn't notice a problem until I attempted to run a complete full tank recently.
(Of course by now it was a lot more hot and humid weatherwise than when I started).

I was trying to get a complete run and use a full tank but just couldn't keep it running.
Everytime I tried to go past 1/3 throttle it would sputter and die.
I checked the usual suspects, fuel lines, tank fittings, correct set up, glow plug etc.
No improvement.
I noticed how hot the motor was, and figured I must have the needle set too lean to get that high rpm sound.
(I had read here that breaking in an ABC engine too rich is bad, the engine needs to run hot to break in effectively).

Well after a few frustrating attempts, I let it cool and changed the needle setting (counterclockwise to richen it).
On my set up, a closed needle valve is at a 3:00 position, the way I was running it was about 9:00, so I reset it for 6:00 position, not as high an rpm sound - but you know what, not only did I run a full tank to empty, it ran great the whole time, never conked out, and the transition from low throttle to high was smooooothh.

And I could run it at full power as long as I wanted with not even a cough or burp.

Ok, so I'm new, maybe I'm wrong, but I figured that at the lean setting I had before, the engine must have been getting hot when I raised the throttle setting - and sagging until it stopped.

Engine Problems!!!!
 

The reason given for the old exhaust baffle was to retain heat in the plug at idle. Any added back pressure was an unavoidable consequence. Back pressure on any engine is NOT a good thing but unfortunately is necessary nowadays simply to provide enough muffler pressure for full throttle operation with the too large carbys that are generally fitted.

Engine Problems!!!!
 

Well, this is the thread I have been needing to read for quite a while. My Hobbico Superstar came with a 40 LA. It started and ran beautifully the first few times it flew. Now it is running rough and quitting in the air after about 5 minutes. It is really putting a damper in my learning curve as I only get half a flight in. I did run it with a OS FS-40 four stroke for several weeks and that ran great. But that engine is now in another plane. Here is what I have done with the 40 LA: Dismantled and cleaned the entire engine, carb and needle valve, replaced the fuel tubing to the tank with larger diameter and a filtered clunk, and just last night I cut away at the plane to allow the tank to be raised up about 1/2". I was thinking I needed more fuel pressure. I was even considering getting a Perry pump. I have fiddled extensively with the needle setting and the air bleed. I have tried several glow plugs. I've tried running with muffler baffle removed.
Anyway, reading this thread I think my next steps are to check for leaks at the needle valve and carb. Unless anyone here would like a near new 40 LA on trade :-)? I wish OS would provide more in the way of troubleshooting, But then OS does have one of the nicest web sight of any other engine manufacturer.

FR

Engine Problems!!!!
 

If i said i have tt, i made a mistake. What i meant to say was i have os, but have heard great stories about tt as well.

Engine Problems!!!!
 

Now this is weird. Last night I removed the 40 LA engine from my plane and removed the carb to clean and check. And what happens? At least a half ounce of oily fuel comes pouring out. No wonder it is hard to start, runs poorly and quits suddenly. I don't think I am running it too rich since I have tried leaning it out til it almost quits. I have a few theories. The first is that my fuel is old (bought it about 4 mos. ago) or dirty from pumping out the tank back into the gallon bottle (I'm down to about 1/4 gallon) or that the engine is for some reason blowing some of the burnt exhaust back down the intake. The last makes sense, since what I poured out of the engine was mostly oil. Lately the engine seemed harder to turn over like it had more compression, but this had to be caused by all the oil in the crankcase. Once it started running it probably couldn't suck the heavier oil into the chamber to burn. Maybe I need a drainplug to drain the engine before each flight :-). I think I will try some fresh fuel and see what happens. Does any of this make sense?

FR

Engine Problems!!!!
 

No. What i think is you are running a really high oil content on an engine that can't use it all. Keep in mind, Fuel is stored in warehouses for years until it is needed, i don't think your 4 month old fuel has gone bad. You can try, and while you are at it, get 20% oil content and see what happens.

Engine Problems!!!!
 

AllThumbs,
All that shifting of the needle from 3:00 to 6:00 to 9:00 is way too much movement on the needle. When leaning out the needle, make small adjustments, and make them slowly. The engine will not respond instantly. It's quite possible that the peak is somewhere around 1:30 (or somewhere), and you are going right from too rich to too lean with no stopping in between.

You want to run a new ABC engine a temp, but you still don't want to overly lean it out and overheat it. The old break-in for a ringed engine calls for running the enigine in a sloppy-rich "4-cycle", that's what you don't want for ABC, but you don't want to peak it out either. You want to get the engine to just break in to a "clean" sounding 2-stroke whine and leave it right there.

Some of the comments I've seen are from guys who say "well, it ran well yesterday, but not today". The correct mixture setting will vary quite a bit with air temp, humidity, and pressure. So it's always good to richen up a 1/4 turn or so in the morning, start the engine, and re-adjust the needle for the weather of the moment. Or at least start the engine and do a pinch or nose-up test to check the mixture, and go from there. Usually, the weather doesn't change much during a day, but if you do go out early and stay long enough to bake (say, 75 with dew on the grass and a light fog at 7 in the morning to mid-90's and bright and dry by 2pm, you can be sure you're going to have to adjust the needle at some point during the day).

Flight Risk,
I agree that it's unlikly that your fuel is bad, but it is possible. You can make fuel go bad in one steamy humid afternoon by leavig the cap off it all day. Fuel will absorb water right out of the air. On the other hand, fuel can be stored for years sealed up, and be just fine. If the fuel looks cloudy in the bottle, it's absorbed water, and is garbage. It can still make running hard if it has a little water in it, but not enough to look cloudy, but frankly, I'd suspect the fuel later on, after other things are ruled out better. I pump back and forth, in and out of tanks all the time, and it does't hurt anything. Yes, a little oil goes up the muffler vent line and back in to the tank, then back in to my gallon, but it's totally ignoreable.

As for how the fuel got in your engine, I'm going to guess it syphoned in there from the tank. I have a couple of airplanes where the tank is high enough that with a full tank, if the lines are primed, the tank will hapily empty itself in to my engine all by itself. Other than that, some oily residue in the engine is normal, and not to be worried about.

It does sound like you're flooded though, so emptying the engine by tiling it up so it drains out he muffler isn't a bad idea.

Engine Problems!!!!
 

SpaceClam,

By the way, a smaller carb throat diameter helps idle and fuel draw, not hurts it. As Downunder said, most modern 2strokes have carbs that are much bigger than they used to be to try to get big power numbers, but they do that at expense of idle.

Losing a muffler in flight will of course cause poor idle. But it's entirely because of the loss of muffler pressure to the tank. If you set up the low speed mixture to be correct with out the muffler pressure, and allow for good fuel draw, you'll find that the idle will go right back to being just fine. The only valid test is to run an engine with muffler but with out the vent line attached and then run it with out the muffler, and see if the idle is affected. As downunder said, backpressure is never good (except tuned pipes)

Engine Problems!!!!
 

I understand that a smaler carb draws more fuel, because of the vaccujm caused by the air moving through it. A smaller hole means that the air has to move faster to get the same amount of air through it in the same amount of time. While i am not certain, i will not argue any further whether you can idle an engine without pressure, Simply because all i have seen is muffler falls off=doesn't run well. I am not sure wether it is because of an unequal pressure or lack thereof.

Hey Montague...on the needle setting....
 

I probably did make too much of a needle setting change, that is true.

I was getting a bit frustrated trying to find a setting to get a full tank run without stopping.
I've been waiting to get a first flight under my belt, and didn't want to have an engine that won't run a tank w/o craping out on me.


Anyway, I have a few questions:

1.) I believe I actually went from a leaner setting to a richer settingg (and not vice versa) as I went "counter"clockwise from a 9:00 position to a 6:00 position (the 3:00 position being the needle closed shut).

The engine isn't running blubbery yet, so I believe it may be rich - but not too rich.

2.) Any chance that I have been breaking it wrong or done some damage by NOT running it lean enough (hot enough)?
I've only got between 3 and 4 tanks of 5% at this point.
And I always tend to worry about running too hot.

Engine Problems!!!!
 

Flight Risk here with an update. I rechecked all hoses and needle valve and carb for leaks. I drained the crankcase from all the old oily fuel. Mounted the engine on a test stand and ran a few ounces of fresh 10% nitro, 20% oil through it. It ran great as new. Mounted it on the plane and filled the tank with the fresh fuel. It started and ran great for about 5 minutes then quit suddenly as usual. I opened the throttle and looked into the carb and the fuel was percolating. I drained out what fuel i could and spent several minutes trying to start it again. It would run 5-10 sec. and quit. Seems like it is drawing in fuel faster than it can burn it and the rest is building up in the crankcase and percolating out the fuel to leave the oil. I have tried leaning out the engine as far as I can without dying. I've tried several plugs. Evidently the fuel isn't the problem. I guess I could try a hotter plug (i've used an A3, A5 and Fox Miracle plug) or try to find fuel with 10-15% oil. Back to the drawing board.

FR

Engine Problems!!!!
 

flight risk....yoiu say the fuel is percolating (boiling?) when the engine stopped. That indicates to me that the crankcase housing around the crankshaft is overheating (and possibly the rest of the engine as well). A plain bearing engine like the LA needs a minimum of 20% oil and strictly speaking all or most should be castor. Most RC fuels have 18% oil but a couple are actually only about 16% because of the way they mix it. Get a good brand of fuel that clearly says on the label just what's in it and how much, then maybe add a bit of castor to be on the safe side (22% oil is ideal).

Engine Problems!!!!
 

Spaceclam...an engine will idle perfectly well without muffler pressure because that's what they all really do. Soon as you come back to idle there's almost no restriction to the exhaust and whatever pressure was in the tank then bleeds back through the pressure line into the muffler. They'll all also run perfectly well at full throttle without muffler pressure too but you'd have to open the needle considerably and then it'd be very sensitive to pointing the nose up so it can really only be done on a test stand.

Engine Problems!!!!
 

that's wshat i have been saying the hole time. iot is probably overheating.

Engine Problems!!!!
 

That is likely your problem, and is the fastest way to ruin an engine. Richen it up. The reason it dies after 5 minutes is that you're running it too lean and it overheats. I see folks at the field do this nearly every day I fly, and they swear up and down at their engine when in fact they're just not running it as they should be.

Do you have any experienced help available? Glow engines take some getting used to.

Engine Problems!!!!
 

MikeL,
I agree completely. FR, everything you've said so far leads me to believe that you're running that engine WAY too lean.

AllThumbs,
Turning that needle valve 1/4 turn is too much when adjusting. One or two "clicks" at a time.

Are you saying that you're needle valve is only open 1/4 to 1/2 turn from closed while running? Something just ain't right there.
Dennis-

DBCherry.......from the OS Manual that came with the 46FX:
 

- which you've no doubt seen and know already (so no revelations here).

Yes, three quarters of a turn open sounds like a whole lot, and very rich compared to what you guys are used to running.
But the OS manual has a diagram w/steps (or needle valve positions) numbered 1. thru 7.

It shows a "rich" needle setting for starting the engine at position number 1).
1.)that is almost 360 degrees for open - or a full turn (from the closed position, which is what I called a 3:00 O'clock position).
2.)begin "leaning" with a clockwise turn of the needle to a point that looks like a 75% or 3/4 turn from the closed (or 3:00 O'clock) position at which the
3.) ....the exhaust note changes.
4.)dissconnect glow starter
5.)advance clockwise (until you hear an intermittent 2 stroke note superimposed on low 4 stroke sound at a point that looks like a half turn open at 9:00 o'lock - from the 3:00 O'clock closed position.
6.)clockwise turn from this point gets a clear high pitched 2 stroke exhaust note, with a practical best optimum needle setting w/in a 20 to 45 degree setting around the 12:00 O'clock position


Anything leaner than that last needle setting is called "maximum rpm setting" - or "Lean".

So, I agree w/you, - I'm obviously running a pretty rich needle setting at a 3/4 of a full 360 degree neeedle turn, BUT that's what the manual says to do.

In fact, it says to do the first three or four flights this way at the 3/4 or 75% neeedle setting in number 2.)above....where the sound breaks into 2 stroke from 4 stroke.

I'd like to "lean it up" for more rpm - but it wouldn't stay running after I advanced the throttle past 1/3 power.

I don't think I want to do dead sticks w/ the instructor for the first three or four flights, which (based on my ground tests) is likely to happen if I set the needle any leaner than 3/4.

The manual says after ten to fifteen flights, the engine should run continously at optimum setting w/o loss of power.

I'm concerned that based on what some of you say, the ABC type engines should be "broken in" hotter (leaner) than ring engines - so I'm not sure how long I should be running it rich like this.

Engine Problems!!!!
 

is your fuel tank mounted in foam? if not it could be foaming up from the vibration of the engine! just a thought.............

Engine Problems!!!!
 

True. I made that mistake because the manual said to do it on my first plane. It said that on my second plane, but by then i knew better than to take them seriously. I switched to a different company, and they said the same thing. I think every kit says to do that, but it will only cause problems. The 46 fx is not ringed. The break in instructions are different for a non ringed engine than for a ringed one.

Engine Problems!!!!
 

does that carb have 2 needles? sounds like the low end one is lean which makes it lean on transition

Engine Problems!!!!
 

AllThumbs....I've looked at that needle setting chart on the OS web site (not owning an OS) and it's very confusing. It's not actually based on the needle being fully closed (because then your engine won't run at all) but it's based on whatever needle opening you need for proper operation. For instance, the maximum lean (or peak) setting at the 3 o'clock position could mean that the needle was open 1 1/2 or 2 turns from fully closed. All the other positions are just a general guide as to where the needle should be to get a certain mixture. BTW, they're also assuming you'll put a file mark on the needle end so you can see how far you turn it. What I do is close the needle (gently) then mark it at the top or 12 o'clock position. Then you can see exactly when you've opened it 1 turn, 2 turns and so on.

The number of turns the needle is opened is going to vary depending on what type of fuel you use (mainly) and most engines need about 2 turns or more to be certain they won't run lean, especially on the critical first start of a new engine where you have no idea how it's going to run. The only setting that's instantly recogniseable is where the sound changes from a 4 stroke (deep growl) to a 2 stroke (higher pitched clean sound). That's the equivalent of what they call the 9 o'clock position but the needle itself could be open maybe 2 1/2 turns from fully closed.

The OS diagram simply means that full lean will be about another half turn closed from that point (once again, more or less depending on your fuel).

Here's some answers to your recent questions...
 

Sorry to be hogging this thread, I should 've started a new thread before running away with this one.

a.)Yes, I have some thick 1/2 inch foam rubber-banded around the tank, open at the top.

b.)Nope, one needle valve on the port side of the carb, and a long upright screw in a spring on the starboard side.
Haven't fooled with that one yet...I let my instructor adjust that the last time I was at the field.
I'll be talking to him again - hopefully tomorrow afternooon.

Downunder, Thanks for pointing out the "relative" position of the settings...which I take is variable, based on the known benchmark, which is the breakpoint from 4 stroke to 2 stroke.

If what you said is true...... <<"The number of turns the needle is opened is going to vary depending on what type of fuel you use -mainly- and most engines need about 2 turns or more to be certain they won't run lean, especially on the critical first start of a new engine">>....then maybe I'm still in a slightly lean setting (instead of overly rich setting) afterall, which gives me a piece of mind according to the current philosophy of breaking in an ABC engine hotter.


I'm turning this "problem" over to my instructor
- he flys YS four strokes these days but he no doubt had to go through the 2 stroke portal to get where he is today.
He's got a good ear too.

Engine Problems!!!!
 

that wouldn't explain the cut-off-in-5-minutes problem. only overheating would.

Engine Problems!!!!
 

AllThumbs...yes, I think you're running far too lean which is much worse on any engine than being too rich. Chances are that as the tank level gets lower in flight the engine continues to lean out until it's at a point where it's too hot to run anymore.

Engine Problems!!!!
 

You have probably trashed the engine by now. Runnning a 2 stroke lean is REALLY bad for it, not to mention freezing up or repeating it. If your engine still runs, It will never produce the power it could have or last nearly as long. I would invest in a new piston and sleeve, and break it in again.