joizeex

Hi, i'm having some issues with my OS .50 that i would like to go over.

1) i've broken it in on 1.5 turns out on the HSN as per manual for a few tanks
2) i've been running with S&W, Byron's, PowerMaster fuels, 15-20% nitro and i believe 18-20% oil. I ran 4 gallons through it. The engine temps were 220F measured at the head right after engine was killed with blades still spinning (yes, i always crawl under them )
3) i got Coolpower 30% and ran 1 gallon, during which it smoked a lot more than other fuels for the first 2-3 tanks, so i leaned it little by little for the next tanks, thinking it was too rich. I measured temps to be 250-260F right after shutting off, for the next 3 tanks, until someone told me that Coolpower will always smoke even when it's lean. The climbout power seemed to be lower than with other fuels.
4) At that point i richened it back little by little for 2-3 tanks until it was at 220F again.
5) Now it would sound really high pitched when i gun it to the top of throttle range and not have a whole lot of punch. At hover (50% throttle) it sounds fine.
6) At this point it started doing some weird things. I can hover around just fine at ~1.5 turns out on the HSN but if i gun it 4-5 times in a row, on the 6th time, the engine suddenly loses power, sounds flat, can no longer lift the heli or sustain hover.
7) For the past 4 tanks i tried leaning out HSN to no avail, although it made it run smoother again, at 220F. I also made LSN slightly richer, again, to no effect on the eventual power loss. The engine does not always sound very consistent and after punching throttle a few times, it just gives up and drops the heli to the ground with no power to go back up. When measured, the temps are 180F which should indicate that it's too rich. The HSN is at 1.25 turns out. The LSN is 30 degrees CW. I have a brand new OS8 glow plug in it. I opened up carb barrel and cleaned it. Fuel spits all over the heli, which along with the temperature numbers, is another proof that it's running very rich after i gun it a few times. Could it possibly be too lean, despite all these indications? it doesn't sputter at that point, just doesn't reach high rpms and sounds flat.

What would cause it to go into fuel overdrive mode? Does my running hot for 3-4 tanks at 260F kill the engine? Doesn't seem like it would happen that quick. And why does this complete drop in power and super rich condition only happen after i punch throttle a few times? I checked all the bolts and everything is tight and there are no leaks that i can tell of. If it's too lean, i did richen it before and it ran even worse with sputtering.
If anyone can help with this, i'd be extremely grateful, as i've ran out of ideas! thanks!

joeyhatch11

Hey Renat, how many gallons should that motor be good for? Can you get the other fuels you were using before this last gallon? Maybe the fuel your running now really isn't what it says it is, maybe too much oil.

joizeex

people have ran 20-30 gals at the least i think. this has only had 5. i guess it's possible to kill it within only a few tanks? i dunno.

i was gonna ask my friend to borrow his Byrons fuel, since he doesn't fly his .30 anymore.

Bax

My Feedback: (11)

"Breaking in" an engine with the needle at 1.5 turns out from closed sounds like the engine may have been run much too lean. The manual only gives initial starting points that are really only rough suggestions. The engine would have had to be run quite a bit richer than that for a proper breakin. If you are not experienced in heli flying, it is very difficult to break in an engine when it's on the heli. You need to be able to run the engine at full throttle while being severely rich. That usually means forward flight and very little hovering. That's because hovering is not done at full throttle.

We ignore temperatures, and have no idea what the engine should register. You must set the engine by sound and performance and then see what temp you get. If the engine is performing welll, then the temp you read is the "correct" temp. If anyone gives you an absolute number for a temp or for a needle valve setting, they've given you wrong information. That may be what their engine gives them, but no two engines or installations are the same.

You cannot gauge your engine's mixture by smoke unless you are intimately familiar with how the engine behaves with the particular fuel you're using. Smoke varies, and depends upon the mixture setting, the type of oil in the fuel, and the amount of oil in the fuel. Change the fuel and you're going to see a different amount of smoke.

If the engine sags at full throttle after running a while, then it's running too hot. No other reason. Overheating is caused by a too-lean mixture setting, air getting into the fuel system, a restriction in the fuel system, insufficient cooling air, too little oil in the fuel, too much compression for the amount of nitro being used, a restrictive exhaust system, and any combination of the above. You'll have to go through the aicraft/engine/fuel system combination to debug it.

If the engine's had enough of an overheat, you may need a new piston, ring, or cylinder liner, or any combination of them. It only takes a few seconds of too-hot running to damage an engine.

joizeex

thanks Bax. So that begs the question: why wouldn't the manual err on the rich side and instruct for 2 turns out, instead? Wouldn't you agree that, that's a huuuge difference in needle setting and not a simple "rough suggestion" away from safe settings? If it should be run at, say 2 turns out, I would imagine i can trust at least the manufacturer to instruct for a safer setting. I don't see why 1.5 turns would be so aweful, because the engine clearly sounded rich and spat out lots of oil during break in and ran under 200F.

I didn't fly around at WOT for break-in, but during hover i did punch throttle and then let off, several times, then landed, let it cool and started up again, during 2nd tank. First tank was high idle on the ground, varying throttle up to 40% and back.

The reason i'm asking about temperature is not to gauge the best performance, but to gauge a SAFE performance. Everyone says to go no higher than 210-220F or the engine will get damaged. Mine ran at 260F for 3-4 tanks, but never higher than that (possibly at 270 for a burst, while in the air, with regular flying and no aerobatics of any kind). It ran at 220-230 at other times, with different fuels, making good power and never sounding too lean or struggling. Considering how temps are specific for each application, it looks like that's what worked for me. What do you consider a max safe temperature for these engines?

I would like to know, from your experience in the field, is that too hot for this engine and enough to spell the end to piston and sleeve? What are the signs of damage on those parts that i should look for? When i looked through the exhaust port, to my not-so-experienced eye, there weren't any caked areas or excessive wear marks on anything. When i open it up again, what exactly do i need to make note of?

It just seems weird that when the engine looses power and i shut it off and measure temps, its well below 200F, so what's baffling to me is how it would be overheating [] The compression seems really good when it's cold. Someone suggested to me to also handcrank it to test it right after it looses power and it's been shut off, to see if the compression is still good at working temps.

thanks

Bax

My Feedback: (11)

We have no idea what temps are good. We don't use them at all when we're testing engines. We go by the sound and performance. How does it idle? How does it hold a needle at full throttle? How does it throttle up and down?

In this thread, http://www.runryder.com/helicopter/t...top=1251814690

Dr. Ben (Ben Minor) a top-level, world-class heli flyer details how to break in an engine for maximum performance. It refers specifically to the O.S. .91 heli engine, but applies to any other engine. Good advice.

joizeex

i'll take a look at his advice, thanks for the link.

i always tuned it by performance and sound, but i always see warnings about too high of temperatures, so that got me worried. it just so happens that mine had good consistent pull, through the whole throttle range, at 230F, so i always just kept it at that tune, until this new fuel caused me to start changing things. []

i'll try to get a video of it today. i'm sure that'll be a lot more descriptive.

joizeex

this is what i posted in another OS thread and i'll copy it here. let me know what you think Bax. thanks!

after partial disassembly:
my sleeve had some different hues where it meets the head, from temperature differences, but nothing that stood out. Overall it was that dark gray/green whatever color. The inside wall still had cross hatch pattern visible and a few light vertical scratches around, but no real scoring. The piston was similar color, but much much lighter grayish color all around, with a tint of very light brown up top and some more brown varnish below the ring on the skirt. The ring was still springy, had some varnish within the ring groove and otherwise didn't have any visible damage. The combustion chamber had some very light brown film that i wiped off completely. The crank rotation is smooth and at no point did i feel any rough spots.

and from today:
so i tried Byrons 15% today for 2 tanks and it worked just fine. i revved the engine on the ground several times 0-100% with slight negative pitch and was then still able to lift off. i also punched it repeatedly while hovering and the old issue didn't resurface. then i flew a whole tank. one thing i forgot to do was try to gauge the compression after running it. the temps were around 180 so i leaned it out a couple of clicks and last run was 200F measured pointing at the glowplug. i didn't try extended climb yet, because i wanted to at least see how it would work for a full tank before i go crazy with it and cause it to drop straight down from loss of power lol.

joizeex

finally got my friend to shoot a vid. yesterday it was worse than ever. at least previously on 30% fuel it would hover and fly and wouldn't lose power unless i would punch the throttle a few times. in the vid i'm using 15% byrons fuel which seemed to have worked flawlessly for 2 tanks after i partially took the motor apart.
http://www.youtube.com/watch?v=Zelo9An87EM
the temps after the first run were about 155F right after shut down. then i leaned it 3 clicks and tried again, result of which you see later in the vid, and the engine shoots up in rpms, yet still has no power to lift off anymore. the temps after that run were only 165F.

so what's the verdict? new ring and sleeve?

Bax

My Feedback: (11)

I don't have sound on my office computer, so I can't tell anything, so the video is not conclusive.

If the engine is sagging, then it's likely overheating for some reason. If the engine's had an overheat at any time in its history, then the piston/ring/liner fit could be loose. A loose fit causes overheating because you wind up over-leaning to get the engine to run well, with a good sound and RPM level...then the engine heats up and sags off.

If the piston and liner are not scored, you can likely get away with a new ring. Then break in the engine carefully. You cannot run it too rich during initial runs. Full-throttle running is best for breakin, but Dr. Ben's method is excellent...and he does his in a hover, which would use less than full-throttle running.

joizeex

yea, the sleeve looked good, it had some crosshatch pattern in it still and just very very fine vertical lines closer to the top (like from fine sandpaper, i'm assuming that's normal wear?). i don't think those would qualify under "scored", would they? Since the engine doesn't seem to go over 160F before it sags, i'm guessing that the ring fit is so loose, that once it gets warmed up to operating temps, it looses compression and power, before it can even get lean and hot. Does that sound right? So i guess i'll try a ring replacement first?
thanks Bill

Bax

My Feedback: (11)

Since we NEVER use temps, we can't say whether your measurements are "correct". O.S. has no guidelines regarding temps. If the enigne's had an overheat, it's likely the ring has lost its temper and isn't sealing properly.

joizeex

did my ring swap today, the old ring was VERY worn out and when i tried taking it off, it broke (i still had the engine/piston inside the heli). you can see in the pics that the width is much less than new ring (right side and top side of the pictures is the new ring). the sleeve looks ok, but in the latter pic you can see a small score line that i noticed only today (exactly in the middle of the pic, ignore the white flakes near it, that's from a paper towel). there were also a few more, less pronounced lines and the rest is just very fine lines. those "bad" lines were at the back of the engine, and i also noticed the old ring was shinier at the back as well, though it was thinner at the front. a bit the opposite of what i would expect, no?

hoping to start re-break-in tomorrow.

joizeex

well i got the heli running and was hovering a few inches off the ground for about 1/3 of the tank and then it started doing the old "dropping to the ground" thing. i had the main needle at 2 turns out and the mixture needle in the middle. the engine seemed like it was revving up just fine but the blades weren't spinning fast enough. which now leads me to believe that it's the clutch. i dropped the engine out and looked at clutch lining and it was glazed with black slippery layer. i scraped that off with sandpaper and i can see that the lining has a yellow stripe in the middle, around the whole circumference. is the lining done at this point? will it be ok since i scraped the glaze off? it really seems like clutch slipping is the cause of this, but i may be wrong.

joizeex

just ran the heli again and after a couple mins of hover it suddenly lost lift. i stuck a tach on the tail boom and then revved the engine between 0-75% and the rotor rpms would increase up to 800rpm, at which point the engine would still continue revving higher and louder, while the rotor stayed at 800 rpm. i would think that's clutch lining going bad, no?

Bax

My Feedback: (11)

To debug your heli, you'll need to ask in a heli forum. We can only offer assistance for your O.S. engine.

joizeex

thanks for all your help Bill.

joizeex

the problem turned out to be a cracked and slipping main gear's one-way bearing. so this whole time it wasn't the engine, but the bearing. although the engine's compression is now improved with the new ring, so once i get the bearing replaced, i should see much better power delivery.

Bax

My Feedback: (11)

We're glad you found the solution to your difficulty.