There's nothing wrong with the new AX series. The carbs are an improvement especially with the HS needle back on the carb where it belongs. The engines seem to run cooler and seem to last much longer except the bearings need to be replaced at the same intervals as the FX. I wish OS would LOSE THE CHEAP STEEL CAGED BEARINGS, what do they save, 20 cents a unit their cost?

I would run the old 46 FX hard for a summer and the power would be down so I'd hand it off to the fist kid I saw for his trainer, still stronger than a LA right?
Then I'd pick up a fresh one for next season.
I now run a few 55AXs and it's been a few years and no power loss, they must have done something different to the piston or nickle plating.

The AX series engines make their power at a little lower rpm the other engines in their size, just adjust the prop size accordingly.

As to the suggested prop sizes in the manual .....are they kidding?