OS 37 Breaking-in Advice

[D22597]

Alright, I'm about to break in a new motor for the first time and just read about 100 posts on the topic. However, I still have a few questions before I get started.

The OS manual states to run needle 1.5 turns past the "normal setting" for breaking-in. The manual also recommends 1.5 turns to start, so I assume that's the "normal setting".

Questions:

I assume the manual is recommending to run the needle at 3 full turns for breaking-in (twice the normal setting)?

How about the idle screw? Keep it default or back it out some too?

All the posts on the topic state "run it rich, but not sloppy rich". Does that mean turn out an extra 20%, 50% or a full 100% like the OS manual is recommending?

Thanks for the help! I think I have enough info from all the other posts I read to get me through the break-in and tuning past this point.

[mdu6]

OS recommendations for break-in are very conservative in-order to avoid a lean run from the start.

So 3 turns on the main (idle kept at normal settings) will be very rich - I normally run only the first tank at this very rich setting. Second run I will start closing down about 3 clicks per run to approach normal settings.

Don't overspeed/overload the engine - but get it progressively running longer and getting to a good working temperature .

[MikeG4936]

You definitely want to build up a bit of heat in the motor to seat the ring properly. I would go 1.75 turns out on that particular engine.

[Rob43]

I cannot imagine it running 1.5 turns extra. I think to get it running, and start a bit extra like suggester here, and see how it responds - noise, power, smoke, sound. Adjust as needed.

[mdu6]

Your 2 points are good - except IMHO they don't take into consideration :

Alright, I'm about to break in a new motor for the first time

Sure - the final main setting will probably be very close to 1.5, but I believe getting D22597 to figure out safely the effect of progressively closing down/tuning has some value

[Rob43]

Yeah, I cannot disagree. I am by no means an expert. I start rich too, but looking at the O.S. 37 manual, 1.5 turns is certainly what they suggest.

In my case, I had someone more experienced to help me get it running and adjusted initially. A mentor who has engine tuning experience would be invaluable.

[Lumpy427]

The O.S. 37 are great little engines! Easy to tune and once you have it set up they are just a motor that you can abuse! Start out with 2-2.5 turns from the closed position. Run at least two tanks, just hover and very little pitch pumps at first. Then on the 3rd tank start to close down the needle by at least 2 clicks at a time until the motor starts to become very responsive.

Both my engines seem to have the sweet spot right around the 1-1.3 turns open. I am using a #8 plug in both of mine. Of course depending on where you are im sure the tune will be slightly different.

What plug are you going to use?

Cheers,
Fluffy

[D22597]

Thank you everyone for the help! This should get me started and there are plenty of existing threads with tuning advice to get me going.

I plan on using #8 OS plug and 30% coolpower. This one is replacing one I bought used that recently shelled, so that's the reason I'm a little cautious.

[D22597]

Well, I put a half gallon through it yesterday and seems to be on track. I started about 2 1/2 turns and couldn't get it to spool up that rich. Slowly took the needle in and eventually realized I had the mixture screw too far out. Once I got the mixture worked out, I was able to float and slowly worked my way to 1.5 turns.

Here is my last flight. Any observations or suggestions welcomed. Not sure I have the mixture setting completely worked out yet.
https://vimeo.com/130014561

[mdu6]

Are you flying out from a country club, I have never seen such immaculate grass ?

Your tuning seems good - not 100% spot on but the video sound/image quality is not good enough to help fine tune it better.

Important point - you are not overheating the engine (when you land go to idle quickly and see how it settles down to idle) - you did it once after a minute or so of flying and it settle down correctly.

Also as important as not overheating, you must still get the engine hot enough to break in. You can confirm this easily by simply touching the engine (the crankcase just below the head). After landing and going to idle, you should not be able to keep your finger there for long - it should be uncomfortable after 1 or 2 second.

If your skin sticks to the engine (!) it's too hot - (but joke aside if it was that hot when you land and went to idle the engine will whine and ping before settling to idle).

If you can keep your finger there and almost feel not heat - too cold (rich).

[D22597]

Thanks! When I landed, I didn't take it down to idle in the TX immediately and should have to prove your point. Right after this video I measured the backplate at 104* F. Is that in the safe zone?

[Rob43]

Pretty cool.

[u8at711]

not all temp guns read the same,
I'm breaking in a ring now. This is what happened.
the first tank is at idle. 1.5 turns on main,

2nd tank is hover, land, idle, hover, idle, a few times, 1.25 turns on main, during these hovers, there was fuel pouring out of the exhaust pipe.

3rd tank hover at low head speed, 2500 rpm HS, 1.25 - 3 clicks.
No more fuel pouring out, but very thick smoke.

The next flights will be at the field doing sport flying, I'll be leaning it one or two clicks at a time., you'll feel the motor running great but keep it a tad rich, the motor will feel as it got richer on its own, keep leaning it to keep it just a tad rich,
My final main needle settings end up about 3/4 - 1 turn out. And that's around 7-10 tanks

[u8at711]

After flying around a bit, maybe after some hard flying, if the motor starts to loose power during flight, get it on the ground and put into idle, if the motor does not goto idle quickly it's lean,
I'll put my finger on the back plate or side of crank case, hold it there for 5 seconds or longer is ok,

[D22597]

Was able to put another half gallon through it today. I'm somewhere between 1 1/2 and 1 1/4 turns. I know I still could lean it in a little more but trying to keep it safe and get the mixture dialed in first.

Thanks again everyone who helped. Here is the last flight of the day and right at 1 gallon through the new motor. The temp was 115*F after I landed and could keep my finger on for 4-5 sec.

NX4 Tuning Part 2 (5 min 28 sec)