Hi i just got my trainer plane and my new OS .46AX. do i need special procedure on breaking-in this engine. the manual Says go on rich setting full Throttle for 1 minute and 10 second interval 4 and 2 stroke setting until tank is empty? is this correct or its better if i let it idle with rich setting for 1tankfull during the first start-up.

thanks....

follow the book you may hear other methods but the right way is the one in the book .
I have the same engine and the thing is a screemer the reason for richening the needle is to cool the engine down through the break in procedure so you dont burn it in you break it in.
after the first runs fly it rich like the manual says your good to go, mine runs super.
one thing to do after every flight/run check the plug and all head bolts for tightness for at least the first ten flights mine loosened up a bit and I didnt notice until the engine was barely running I got it down after tightening the bolts and plug not any problems with this motor

the manual (breaking-in portion)
1.install the engine with the propeller intended for your model. Open the needle valve to the advised starting setting (which is 2 complete turns from closed) and start the engine. if the engine.... and the next sentence. run the engine FOR 1 MINUTE WITH THROTTLE FULLY OPEN, but with needle valve adjusted for rich slow four-cycle operation.
2.Close the needle valve until the engine speeds up to 2cycle operation and allow it to run for 10 seconds then reopen the needle valve to bring back 4cycle operation and run it for 10 seconds. repeat this procedure until tank is empty....

am i understading this correct? run the engine with THROTTLE FULLY OPEN FOR 1 MINUTE in rich setting right after starting???

thanks for the replies and tips in advance...

Yes. With an ABC or ABN type motor you are making the piston and liner break-in to one another. Hence if you ever have to replace either the piston or liner, you replace both as a set.
With a ringed motor the break-in is totally different, much lower rpms till the ring seats itself to the liner. Then ya let her rip!

sounds scary.... but if that how it's supposed to be done then Full throttle it will be right after starting... thanks guys...

With an ABC or ABN engine, the heating and cooling is what sets the surfaces.
This will allow you to get max power from the engine.
Not doing it may cause you to loose some RPM but not enough that it will keep your plane from flying.

Yes, run them in at full throttle because it's not the same as a car or motorbike (if that's what's giving you concerns) where you'd never drive them flat out straight from the showroom .

If this is the first time you've run an engine then you mightn't know the different sounds an engine makes when it's either 4 stroking or 2 stroking. When it's 4 stroking the exhaust note is like a lowish growl with quite a lot of white smoke but 2 stroking is a much higher pitched steady "scream" with less smoke. You should remember that a lean setting is bad for the engine, even after it's run in, but there's a couple of easy ways to check if it's rich or lean. Start it up with the needle wound out the 2 turns as they say, go to full throttle and wind the needle out a bit further (maybe a 1/4 turn). If the revs drop then you're on the safe (rich) side. Or after going to full throttle you can pinch the fuel line closed for about a second or less. If the revs rise for a moment then you're running rich but if you keep the line pinched for too long then the engine will just starve for fuel and stop.

As a guide line for your engine, and it really depends on what size prop you use, it'll be on the break point between 4 stroking and 2 stroking at around 10-12000 revs.

As others above have stated, you can't go wrong following what the manual instructs you to do. Follow their instructions and you'll be rewarded with a good running engine.

Ken

the OS .46AX, is it a reliable engine? in terms of differences in cold or warm weather, level of humidity, air pressure? just wondering cause i would want a reliable engine for a first plane.

Yes, the 46 AX is a very reliable engine. Most all OS engines are very reliable. Once you have the mixture set it will very rarely change unless you get a drastic change in the weather you won't have to touch the needle settings.

Ken

thanks for the replies. hopefully i can properly break-in this engine next week.

You can't go wrong speedy. I fly mine all year in all weather and it runs great. It doesn't even seem to mind eating some snow or rain on occasion...not that the weather is ever bad here

I must have broken in about 10 of them in the last year. Yup, what the manual suggests works great. With the last couple, I've only felt the need to do the breakin for one tank's worth of fuel. Yes, you do the breakin needling with the throttle open completely. You're controlling the revs with the needle. And the first tank is to do the "needle dance". I then run a tank to test the lowspeed needle setting. So the engines are getting one full tank on the ground and usually about another half tank running on the ground while I check the throttle up response and sometimes dink the low speed needle.

I've found that the trick that makes the breakin completely safe is with the needle going from rich to lean. Move the needle slowly and as soon as the engine goes into 2cycle pause. Then go slowly from click to click and as soon as you hear any slowdown go a couple clicks back rich. It'll usually be picking up speed each click. After awhile I could tell that one of the clicks didn't pick the speed up. When I started noticing that, I used that for the 10second fast run.

I let the engine cool down completely after the first tank. Toward the end of the tank, I get an idea where the highspeed needle wants to be. I leave that setting and let it cool down. The next tank is for idle adjustment. The pinch test works great. It usually only takes a couple of tweaks. A couple of engines were good to go without tweaking the lowspeed.

None of them have given problems on their first flights other than having too high an idle setting on the TX. A couple have needed the lowspeed leaned out a bit after a couple of flights. It might be that they weren't completely broken in with one tank, but they didn't let the airplane down, and the highspeed needle setting was sufficiently rich to be safe for the engine for sure.

They're excellent engines. You often do "get what you pay for".

Saturday was 11 degrees in Anchorage as i recall.

I never could understand why someone could read a manual produced by a manufacturer of tens of thousands of engines and then question whether or not the instructions were correct or not. Do you think they are going to deliberately lie to you just so they can do free warranty repairs? [:'(]

I've also been breaking in and doing some flying with my new engine - an OS 50 SX but have two questions.

1. I have it set good and sloppy rich for right now with plenty of white smoke. It is probably OK to start leaning it out a bit, as I've had at least 8 tanks of fuel through it. I have not touched the idle/low speed setting. When I go from full throttle to idle, it initially idles quite fast but will eventually (8 seconds or so) settle down to a low idle speed. And, after idling a while, when going to full throttle, the engine will hesitate/cough before returning to full throttle speed. Does this mean my idle/low speed setting is too rich?

2. OK, this is dumb, but where is the idle/low speed adjustment? The manual mentions it, but does not show where it is on the engine (brilliant). The only thing on the carburetor that looks adjustable is the throttle stop screw.

I need to correct this problem before I go flying again, as flying with an unadjusted engine is courting disaster.

Thanks.

Coastie

the low speed adjustment is on the side of carb where throttle arm connects....screw is in center of arm

thanks...

do as other suggest

But i suggest you use an Infared Heat Gun to check the temperatures around the glow plug, for a car they are apprx 230 farenheit?

In reply o Coastie,

Yes your idle is too rich!

This isn't an issue with airplanes. Honestly, we just don't have to worry about engines getting too hot in an airplane. I understand that the car guys have to worry about this, but because of how engines are mounted on planes they don't normally overheat. Heck, I'd bet that you would have a difficult time finding something to check it at 99% of the fields out there. I know that nobody at the fields I fly at has one!!! If you run the engine a little rich you'll never have to worry about it overheating.

Ken

Exactly. We have a slight advantage over cars when it comes to setting the mixture because we can run a plane engine full throttle for virtually as long as we like without doing any damage (lower revs and lots of airflow) but this can't be done with a car engine. Car engines are doing what we'd call a shaft run (prop breaks/flies off but engine keeps on running).

Ya did good by running this engine SLOPPY RICH. Remember that this is a ringed engine and requires a different breakin than most of OS's engines. A lean run will have disasterous results so stay on the rich side. OS tends to ship their carbs with the idle mixes on the rich side to protect the engines until they get tuned in after breakin.
I've got one of their 50's and it's a great little engine.

Coastie: Look at your throttle arm on the side of the carb. In the center, there is a hole there with a screw head depressed inside. That is your low speed needle. Only use small adjustments with this, like perhaps 1/16 to 1/8 turn at a time. With this needle, a little goes a long way. Of course, with a rotating prop, this is best done with the engine shut down.

DS. (also coastie, but retired)