TPL33

Bought an OS .65 LA and was reading through the instruction manual. When breaking in (running in) it says to start the engine, open throttle to full, and start closing the needle valve a little at a time until optimum RPM's are reached. I understand all that. It also say's to run a full tank of fuel through the engine prior to flying. Do you run the engine at full throttle while breaking it in and using a whole tank of gas or do you vary the throttle and do burst of full throttle, followed by less throttle, then back to full? The manual doesn't specify what RPM's or throttle position (fully open, half, idle) to run it at while running the full tank through it. Thanks.

jester_s1

You run it full throttle and very rich. You'll notice if you start the engine at the recommended needle settings it will run very rough and spray a lot of residue out of the exhaust. Twist in the needle valve until you hear a sudden improvement in the sound. The difference will be pretty dramatic, so if you don't get that transition in maybe half a turn or so try turning it out more. We call that rough running "4 stroking" because you have so much fuel going through the engine it's only actually igniting every other stroke. The transition to smooth running is called the 2 stroke break, and it's the richest mix you can run and still get ignition on every stroke. That's the place where you should run in the engine, because it puts enough fuel and oil through it to lubricate the liner and piston so they burnish together and to cool the engine enough during that high friction first few minutes. Don't run the engine at the 4 stroking setting any more than you absolutely must, because it will actually cool it too much and keep the liner from expanding properly at the top. After that initial run it, let the engine cool back to ambient temp and start it again. Tune it about 1000 rpm rich at full throttle (if you are pinch testing, that will be an easy to hear increase in RPM), then tune the low end to get a good idle and transition. The engine should be able to idle low enough to not pull the plane, and should hold a steady RPM for at least 30 seconds. If it won't, either your tuning is off or you need to run in the engine some more at 1000 rpm rich. Once you're flying, you'll find that the engine becomes more consistent to tune and will hold a lower and steadier idle during the first 4-5 tanks. During that time, keep your flights to about 5 minutes and retune between flights as the correct setting is likely to change a bit. After those first flights, you can go a little leaner, about 500 rpm off peak should be right. That will allow the engine to still have an optimal needle setting when it unloads in the air (turns more RPM in flight than on the ground).

thailazer

jester... That all sounds good. In your experience, once you have the high speed needle set after a few tanks, how do you set the idle mixture? After idling 30 seconds and doing a pinch test, do you expect the engine to quit almost immediately, or do you want to hear the idle speed up for 5 seconds before it quits. I've always wondered which end of things it is better to err on with idle settings.

Gray Beard

My Feedback: (-1)

In the LAs I have never had the .65, just the .40 and .46. I would like to see what Bax has to say about there break in for the LA series. I have always just run them up to max RPM and opened and closed the throttle, set the idle then after that first tank of fuel just fly the plane. The higher end engines I take the time to break in but not the LAs.

speedracerntrixie

My Feedback: (29)

The main concerns while breaking in an engine is to get it up to operating RPM and temp. Being tight it will tend to want to run hotter so a slightly richer setting is required. To get the RPM up in the normal operating range you need to lessen the load with a slightly smaller prop. Running it overly rich will keep the temps too low, you want all the internals to expand to normal operating tolerances. Do not run the engine on the ground at full throttle for a long period of time, it will get overly hot and injest dirt. With todays manufacturing processes most engines do not need a lengthy break in. Run one tank on the ground cycling the power from high and low. From there you should be able to get a reliable idle and transition. Go fly the engine at a slightly rich setting. Over the duraration of the first gallon of fuel you will notice the need to slightly lean the low and high speed needles, it will also start using less fuel as well.

jester_s1

My way of setting the low end doesn't even use pinching the fuel line. I get the lowest idle setting that will keep running for more than a few seconds, and I listen. If the RPM's drop during the first 10 seconds or so, it's rich. If it runs for 10-15 seconds and quits abruptly, it's lean. My standard procedure is to start with a rich setting, then turn the low speed needle 1/4 turn leaner after every 10 second test. With each tweak, the RPM will likely rise as I get closer to the optimal combustion mix, so I'll lower the throttle setting to keep it close to the minimum the engine can handle. At some point the engine will go 30 seconds with a very steady RPM. If I get a sudden deadstick I try again, and maybe back off 1/4 turn. Fine tuning the low end goes to much smaller adjustments to get the idle super steady, then setting the minimum throttle position up a tad to get 1 minute reliability, then tweaking the lsn to make the engine transition right from idle to full throttle. On that topic, you want to be able to take maybe 2 seconds to open your throttle all the way and get a steady rise in RPM. On a fully broken in engine, slam it open. You should hear a strong exhaust note as it accelerates. If it goes silent for a second and either quits or starts back, you lsn is too lean. If it makes a gurgling sound like it just can't accelerate, the lsn is too rich.
On many engines, the lsn setting affects the hsn. In that case, anything more than 1/4 turn of adjustment on the lsn should be followed by retuning the hsn before checking anything.

jaka

Hi!
It's very simple! As it is an ABN engine you start it at idle (Throttle open aprx 2mm) and then give full throttle as it starts then and adjust the high speed needle so that the engine rews at a farly high rpm! Not bludderng rich and not at max rpm , but at a couple of thousand rpm under max. The important thing to remember it to let the engine get varm enough ,fast, and that has to do with how the cylinder is expanding away from the piston at high temperature. If you run it at bluddring setting (rich) the temperture isn't going to be right, and the engine take longer to run in (the engine isn,t treated right)

Dreddi

My Feedback: (3)

Just a note; The short bursts of wide open throttle, then back to low power, then wide open again, is for a ringed engine. The purpose of this is to increase cylinder pressure as much as possible (which is highest at low RPM with high power settings or in most cases, during acceleration). The higher cylinder pressures force the piston ring against the cylinder wall and allows the honing (the X shaped surface machined into the cylinder wall, similar to a very fine file) to seat the ring creating a very tight seal. This is done right after a new ring is installed (like on a new engine or top end work), once the edges of the honed surface is worn down it no longer provides this "filing" effect and then serves only to hold an oil film for lubrication.

Now for the non-ringed engine like what we have in our glow engines, ABC, ABN. since there is no ring to seat we dont have to worry about seating a ring, our only concern is the interference fit at the top of the cylinder. The cylinder is designed to be "zero" clearance at operating temperature, which allows an oil film to provide the seal we want. This is achieved during the first few min of engine operation. If you look at a zero time engine you will see the same "x" pattern honed into the cylinder that you find on a ringed engine and it serves the same purpose initially to "file" the piston, then to provide a surface to hold a lubricating film. The key to getting this proper fit is to start the engine, get it to operating temperature as quickly as possible, then allow the engine to run at stabilized temperature for as long as possible while the clearances are worn into the piston. Again once the edges are worn off the honed pattern they no longer provide this "filing" effect.

now, since I have time I can go through step-by-step how (and why) I break-in every engine I break-in.

With the engine at factory needle settings and full tank of fuel start the engine. Once its started bring the engine to full throttle and from now on thats where it stays until it runs its self empty. Once at full power lean the high end needle for peak RPM and maintain this setting for 10-15 sec. This brings the engine up to operating temperature as quickly as possible. We dont want to leave the engine this lean for more then 25-30 seconds, two things will happen. The engine will over heat, we wont be providing enough lubrication for the piston in the cylinder which will lead to scuffing, especially at this critical time in its life. After the 10-15 seconds richen (out) the high needle until the RPM drops roughly 1,000-1,500 RPM, you're looking for a rough running engine (the engine is actually starting to fire every other stroke. "four cycling"). Run the engine in this condition for about 1 min, this is to provide plenty of lubrication for the honing process. After about 1 min in this condition the engine is starting to cool off to below normal operating temperature and we need to get it warmed back up. Again lean to peak RPM and hold for 10-15 sec. Then repeat the rich running cycle for another minute. Repeat this process for the entire tank. At the end of the run and for a gallon or two afterword you will/may notice the oil on your airplane to be blackish. This is the aluminum from the piston as its being broken-in and it will go away. After this first tank you can fuel up the aircraft and restart the engine, adjust the high needle to peak RPM, then richen it back up until you note a drop of about 200 RPM and can see a trail of exhaust smoke. This is the perfect place to run the high end either for the rest of the engines life or if you're into high performance, until the blackish oil stops or 2 gallons, after-which lean to peak, richen for 50 RPM drop and let'er rip.

As far as idle/low needle. I've always set the high needle to where I'm gonna run and then let the engine idle for 30sec and then go to wide open as fast as possible. If the engine dies right away its too lean, if it sags or sputters its too rich. I'm looking for an engine that will go from an extended period of idle to full power with no hesitation or stalling. There are some that do the pinch test but i've found that setting still a little too rich for me. Once I get idle settings set, recheck high needle settings and if needed readjust (low will affect high but high wont necessarily affect low, depends on carb design) then recheck low... once both are good and no adjustments are necessary, go fly.

jester_s1

I'll agree to Dreddi's procedure expect for one thing- 200 rpm isn't enough rich for many engines, and isn't rich enough for any new engine. "New" would be anything that doesn't have at least 5 tanks of fuel through it. The reason being that every engine unloads a bit in flight, meaning that it turns more RPM. The difference can be just a little in cases of draggy airframes and low pitch props where most of the loading comes from the drag of the blades being swung through the air, or it can be a lot with slippery airframes and high pitched props. How much prop you are running has a big impact too. If you overprop your engine, it won't unload as much as if you prop it for max power or under prop it a little. Our engines need to be set a little bit rich on the ground to allow for this unloading, so the final test is to see how the plane flies. To give an example from my hangar, my Kaos unloads a lot with a TT .46 Pro and a 10x6 prop. It needs to be set 1000 rpm rich on the ground to get maximum speed in the air. I've experimented with it using a tach to get the setting right and have found that I'm down on power in flight if I go to 500 rpm rich on the ground, indicating that it's too lean in flight. But my Ugly stick running a ST G90 and a 13x8 prop doesn't unload much, so it flies best set 400 rpm rich on the ground. With a new engine, you should allow for the unloading, plus a little more to keep the engine slightly rich when in flight to provide that little bit of extra cooling and lubrication as everything runs in.

TPL33

OK, did the Breaking In procedure as you described above and it went well. Now the idle. I set the idle using the trim on the TX. It will idle, but roughly when idle is set low enough to keep the plane from rolling. When I set the idle so it's not a rough idle, it's too high and the plane moves forward. I know the point of idle is low enough for the engine not to die but not so high that the plane will roll. When set at where I have it, a rough idle, the engine transitions smoothly from idle to full throttle (no lagging, no sagging, no sputtering), but I have to increase the idle (move trim lever up) to keep it running. If going by the OS instruction book, when I hold the nose 15 degrees up at idle, the RPM's drop, then I point the nose down and the engine dies. Summing it up, high speed needle is set right-peak RPM then opened slightly back to richer. Idle is very rough running, eventually dies unless I increase the idle. How do I achieve a good idle.

thailazer

If you have a rough idle I suspect you are still too rich on the idle setting. A lean setting would be very smooth until it suddenly just quits. Try leaning more on the idle screw until it does indeed not idle, then start to enrichen and see how that works out. With a rich setting, you have to have a higher idle to kick out the excess fuel. A lean idle adjustment allows much lower RPM idle speed. Good luck there and be patient. As your engine breaks in and you get more used to it, all this should become easier. Always takes me a while to dial in an engine and understand it, but I am still learning after 30 years in the hobby.

TPL33

The engine is a OS .65 LA. It has a high speed needle valve and a carburetor Air Bleed screw. Are you saying to adjust the carburetor air bleed screw? Do I make this adjustment while the engine is running and at idle, or, do I keep stopping and re-starting the engine until I get the correct idle?

thailazer

It is safest to stop the engine and make the adjustment. Doing so while the engine is running is risky but I have done it that way. You might try opening the bleed screw all the way and see how it idles.

jaka

Hi!
You do all adjustments idle adjustments wÃ*th the engine stopped. At least on air-bleed carbs.
But remember! All adjustments are not worth anything without having the tank mounted right (according to the tank mounting rule), the tank size right, prop size right, glow plug right and fuel right.
So lets go!

Tank should always be mounted with the centerline going through the carb when plane sits horizontal.
In your case a 300-400cc tank is right. Preferably Uni-Flow set-up.
Props in the range: 11x8,12x6,12x7,13x4,13x5,14x4 depending on plane.RAM, APC or Graupber "Sonic" are the best.
Fuel: 5-15% nitro.
Glow plug: OS 8 or Enya 3.But there are others equally good like Nova Rossi 3 or 4 or Rossi 3 or 4.

TPL33

Wow, things sure use to be easier! I stopped flying in 1990 and started again this past December. Back in the '80's thru 1990 (when I was flying a lot). I can remember building the airplane, taking it to the field, putting in fuel, starting the engine, leaning it out until it sounded good, setting the idle with the control linkage and throttle trim, then fly-fly-fly. No break in, no low idle adjustment, just lean it and fly. Have the manufacturers changed the way they make engines since I've been out of the hobby? I would imagine, like anything else in the world these day's, they probably made them better back then!

jester_s1

Oh they're a little different, but your method still works now as well as it ever did. ABC engines only take about 5 minutes to break in, and even a rich first flight will get it done. A proper break in on the ground with the mix set right for it will prevent liner peeling or premature wear though, so it's worthwhile. But IMHO, flying a plane that you haven't set the low end on and verified that it's right just isn't smart. There's no reason to chance a deadstick or engine damage from a lean run when it takes so little time to make sure the needles are set right and the engine is run in right.

TPL33

Don't get me wrong, I understand the reasons for the break in and the needle adjustments, I just don't remember doing all this "needle" tweaking in the past. In fact, I don't ever remember having to mess with the low speed needle/Carb air bleed screw. Regardless, if I want to fly right, I best get 'er done!

Gray Beard

My Feedback: (-1)

I must be doing it wrong too, I always adjust my engines when warmed to operating temps and while running. High end first then the low end then just fly? Once I have an engine set I don't bother twisting the needles again unless I change the prop size or we have a huge weather change. From summer to winter my high end needle only moves about 4 clicks and I almost never touch the low end. I do use a tach once in a while with a new engine. I have one gas engine I adjust with the engine off but just because the needles are facing the prop and there is only an inch of room between the prop and carb. All others I adjust while running. I tend to not over think things or make more work then needed.