I could probably get good advice on this at the field but I need a wider view. Anyone have experience breaking in the new O.S. 46 AX? It's going into a WM T-34 for pylon racing.

No experience on that model but I managed to break in all 8 of my other OS engines by following the directions in the manual

Whatever you do, don't run it too rich. There are dozens of threads talking about this. Run rich but never fourstroke it. Just run it rich in 2 stroke mode. Once again, DON'T follow the instructions if it asks you to run it so rich that at full throttle, it goes into fourstroke mode, this will inevitably ruin your engine

I concur with "forestroke" on this. Another thing we have found based on experience is to run a gallon of quality castor based fuel through before using synthetic, more power in the long run and longer life.

Enjoy your engine
Alan

I agree with fourstroke, though I think saying running it 4-stroke rich "will inevitably ruin your engine" is a bit harsh. I won't ruin the engine at all. It will open up the piston/liner fit and result in a loss of a bit of RPM, maybe as much as 1.5k, but probibly less. For sport flying, you'll never notice. However, you did say you want to race the engine, so you want to avoid it.

As a side note, when you start the engine, run it up to full power promptly. Let it run at full power for a couple of sedonds, then back off to idle. Don't start it and go right to idle. You need the piston and liner to warm up quickly, running for extended periods at idle, or idleing when cold has the same effect as extended 4-stroking on the motor.

Just taken delivery of my trainer artf kit including OS 46LA

In the breakin instructions it says to promptly move the throttle to full open, it then goes on to say run a full tank of fuel through the engine at a slightly richer than optimum setting. It does not say what engine speed to run it at, surely not at full throttle for a full tank of fuel??!

pete

Yes. Let it run through the entire tank at full throttle.

Well that 46LA manual is really quite dramatic. Is it okay to run it "slightly" rich for a full tank on it's first tank? I would still run it up to full throttle, run it the level just lean of where the engine begins to pick up rpms and run it at quarter throttle for a tank...

Slightly richer than optimum? Isn't that already the way you should be flying it? (three clicks rich from optimum rpm or 200rpm less than max)

If you don't run your O.S. Max .46 LA at full throttle during the breakin process, you won't get it broken in and you'll have an engine that will likely have a much-reduced service life. The main caveat is to not run it in "four-cycle" mode.

You can always tell if you are rich of peak by the fact that a quick pinch of the fuel line will give you a jump in RPM.

Please check the O.S. FAQ page:

http://www.osengines.com/faq/product-faq.html