The engine is OS 46 AX.

If I open full throttle and close/adjust the needle valve till it reaches max rpm the cylinder head is getting hot, is this normal?

If I open the throttle at once the engine is not hiking up/missing a bit, it goes decisively to high rpm

Break in today, started it, open full throttle and open the needle valve until it reduced rpm to slowest I could. the engine was working in four or more stroke cycle, it threw unburned oil and fuel out of the exhaust, the cylinder head was cold all this time.
Every once and a while I closed the needle and the rpm went up, this I did for three tanks.

So how do I make my engine work on its strongest side and last longest?

Thanks
Alex

G'day Alex,
Find a club, & get an experienced pilot or instructor to show you & explain to you how to tune an engine, he/she will also check out your plane, if you have one, & adjust anything that needs adjusting, & then will fly the plane for you, & trim it so it flys straight, then you can start learning, with the best possible chance of success.
But the bottom line is GET HELP, you won't regret it.

I am not familiar with this engine, but here is a little info. If the engine is not a piston engine, you don't want to let it four cycle for too long as these engines need a bit of heat in order for its parts to mesh correctly. Otherwise, the way to reach your peak rpm with out over heating your engine is as follows. Adjust your engine for its peak rpm and then simply back off of the high needle an 1/8th or even 1/4 turn (rich). While flying the engine will naturally pickup rpm as the engine unloads. I usually will back of the high needle 1/4 turn and fly the plane and attempt to judge if it unloads to its top speed. I will then lean the needle an 1/8 of a turn, fly the engine and compare with the previous flight. If the second flight is not significantly better than the first (@ 1/4 turn rich) I will operate the engine at the richer setting. Of course you must experiment with several different size props, both diameter and pitch if you are looking to getting max performance for a given engine. Good luck.

your needle valve is just like any other screw...rightie tightie or lean...lefty loosey or richen...so now that you have run a few tanks through the engine, try this...go to full power and lean out the mixture by tightening the needle valve...you will hear the engine getting faster..it will eventually peak as you continue to lean it out and start to slow back down..stop right there now richen it back up until it's back to peak RPM stop.... now richen the needle valve 1/4 turn...
alan gave the best advice find a club that will help you....

You should not run it full lean for long for a couple of reasons. It will get very hot and sieze, and it will not run during flight. It will quit running, probably at the least opportune time. So, follow jetmech's advice and run it slightly rich. If when flying, it sounds like it is going into four-stroke, not going to full RPM, land it and lean it out very slightly, only a couple of clicks and try it again.

And, follow Allan's and Jetmech's advice and get some help.

CGr

The first flight of each flying session should start the same way.

Start the engine with the trottle just barely cracked open.
When it starts, let it run at that setting while you put aside the starter and kit and until you've moved behind the model. That should warm it up some.
Open the throttle and let it run a moment.
Slowly open the needle valve until you are sure that the engine rpms are slowing. The mixture is rich for sure, and the needle adjustment is starting from an absolutely safe adjustment.
Slowly close the needle valve until the engine reaches it's max rpm.
You will know it's at max when it starts to slow down from being too lean. Immediately upon hearing the slow-down, back the needle out 3-4 clicks.
Now the needle setting is still too lean to fly for most engines. You're at or near max rpm on the ground, but the engine unloads in the air and this setting will not provide enough fuel in the air.
If you see no exhaust smoke, the needle is definitely too lean for flight.
Richen a couple of clicks and fly.
Now comes the important part. If you do not see exhaust smoke in flight, land right away and adjust the needle out a couple of clicks and look for exhaust in flight again.

You're not done yet.
Remember how many clicks out from max rpm you've put on the needle adjustment in order to get a good setting for flight. After a few outings, you'll have a good idea how many clicks rich to take the engine during that first needle adjustment of the session.

It takes longer to type than it does to do it. And it's really simple and easy to do.

Thanks alot, now it makes sense.
I'll do it today or tomorrow.

The best $20.00 I spent is on a tach.