I believe you said you have both makes. - OS and TT.

I have two trainers...a Telemaster 40 w/ an OS 46FX, and an Eagle 2 with a Thunder Tiger Pro 36.
The Thunder tiger is used (Ebay) and fortunately it runs like a Swiss watch, starts with a hand flip. Great engine.(bought a used TT Pro 46 too).

I have been breaking in the OS 46FX since early spring with 5%, and didn't notice a problem until I attempted to run a complete full tank recently.
(Of course by now it was a lot more hot and humid weatherwise than when I started).

I was trying to get a complete run and use a full tank but just couldn't keep it running.
Everytime I tried to go past 1/3 throttle it would sputter and die.
I checked the usual suspects, fuel lines, tank fittings, correct set up, glow plug etc.
No improvement.
I noticed how hot the motor was, and figured I must have the needle set too lean to get that high rpm sound.
(I had read here that breaking in an ABC engine too rich is bad, the engine needs to run hot to break in effectively).

Well after a few frustrating attempts, I let it cool and changed the needle setting (counterclockwise to richen it).
On my set up, a closed needle valve is at a 3:00 position, the way I was running it was about 9:00, so I reset it for 6:00 position, not as high an rpm sound - but you know what, not only did I run a full tank to empty, it ran great the whole time, never conked out, and the transition from low throttle to high was smooooothh.

And I could run it at full power as long as I wanted with not even a cough or burp.

Ok, so I'm new, maybe I'm wrong, but I figured that at the lean setting I had before, the engine must have been getting hot when I raised the throttle setting - and sagging until it stopped.