markhamregular

I just bought an OS46 AX with ball bearing. The engine started on the first touch of the starter. So I did the "brake in" at homeas specified in the book by running lean and then rich every 10 seconds. I did a fuel tank like that and then,I run another full tank. Everything went very well.
When I got on the field, I noticed the burnt fuel coming out of the muffler was brown.
Also, the engine tend to die if you either accelerate or decelerate.
What would cause the burnt fuel to turn brown?

Thanks,

MinnFlyer

My Feedback: (4)

First, what kind of fuel is it? Brown oil is not uncommon.

Look inside the carb to be sure it opens fully, and when closed, there is a slight opening in the barrel (Like maybe 1/16 - 3/32 inch)

The next thing to do is to start the engine, open the throttle to full bore and adjust the high end. Lean it out till it peaks, then keep leaning until you hear the RPM start to drop, then back it off to where it first peaked and open it another 2 or 3 clicks.

Now, slowly bring it to idle. If it starts to die, stop reducing it and try to maintain the lowest RPM that it will hold reliably, then pinch the fuel line. If the engine dies right away, it is probably lean on the low end. If it runs for a while, then gets a significant increase in RPM for a few seconds and then dies, it is probably rich on the low end.

Ideally, when you pinch the fuel line, you should get a slight increase in RPM and then the engine will die (Same as if it's rich, but for a much shorter period)

The Low End adjustment is in the center of the throttle arm. Turn it out to richen and in to lean. Only turn 1/8 turn after each try and after each adjustment, bring the engine back to full throttle and readjust the high end.

TedMo

What Minniflyer has stated is exactly what you should follow to tune. It takes some time to become familiar with how they should sound and what to adjust so just be patient. The oil from these engines is their main undesireable distinction. Just get used to it or go electric. Also it takes many more tanks of fuel to break that engine in. It can be done in the air though.

SCOTT42

My Feedback: (1)

Thats a great engine, Ive got 2 of them and love em. Allso I was toaught that if your oil is brown then you are to lean as it it burning it, But thats what I was told!

markhamregular

Gas is a green one. When I got home tonight, I would look at specifics. I bought it 2 months ago. Is it old already?
I ran the engine opening up 2 full turns. Then I would close it slowly until it starts racing at that 2-stroke sound.
I love the engine too. The one I had before the LA I did not like it at all.
But that brown burnt fuel concerned me a bit.

jetmech05

I had a brand new OS 60 FX that after a few flights I started getting brown to black oil residue......concerned I called OS and was told it is not uncommon.....I flew the engine for years wih no problems....
Be careful trying to tune a new engine......I feel that a glow engine isn't broken in until there is at least 10 to 15 flights on it.....Instead run it a little rich at first and let everything set then tune it like Minn said.......Just my opinion

markhamregular

I am glad it is not uncommon. I have a Cool Power synthetic 10% green stuff.
I actually have run only 2 tanks of gas, and I have not flown the plane yet.
So, I have to continue running it rich (1.5 to 2 turns opened ) I guess.

Thanks,

jetmech05

Don't run it so rich that you dead stick every time you try to fly......just don't try and tune it to max...a little rich from there......then don't do any wild manuvers yet...get those 10 flights or so before you tune it to max

JohnBuckner

My Feedback: (1)

As the fellows have mentioned you are not having a problem and while the engine is not broken in fully it is only neccessary for you to run just several tanks as you have done before the first flights.

Also running any ABC or ABN engine such as yours excessively rich during break in is not good practice. You are following the instructions which is great but now come time to fly please have your mentor check over the tunning as well as good running procedures and I normally do not recomend the folks even running their engines untill they have some one to mentor them as that will prevent so many problems.

I am a major fan of the AX series with three .25AX, three .35AX and one .55AX.

John

TimBle

Yip, not too rich as it actually creates more wear and will ruin the engine.
I like 11x6 wood props on these fir run in since they're a lot lighter (around 17gr vs 40gr for plastic)