Im jumpin on the OS bandwagon as well. I hve two of the 55AX motors and love them. I did notice the midrange issue but it quickly went away after it broke in. Right now I have one in a EF Chinn Yak and it throws it all over the place. It is about to come out though because I am switching it to a Saito .82. I am putting the 55AX in my TH trainer. It is scary fast with the 55 in it. I use the tower Muffler as well and it is one mean sounding trainer.

awesome engines!

RPM numbers are fun to look at when you are bored but ultimately they don't mean squat. It all boils down to how the engine runs and the airplane flys. I generally buy an assortment of suitable props for an engine, fly them all and stick with the one I think is the coolest. Not scientific but it works.

If you haven't bought that .82 yet, take a look at the OS .81 4-stroke. It costs a little more but so far mine seems to be swinging the same props much better than my Saito .82. Runs better out of the box and nicer to dial in as well.

<blockquote><p align="center">I just got a new 55AX on my hanger 9 twist. Can I break it in on colder days or should I wait till it warms up above the 32 mark.
Have the itch to run it. Just thought I would ask.</p></blockquote>

I say run it.

Do you think the .55AX can pull a 7 pound Phoenix .55 size F4U Corsair around pretty well? .55 is supposed to be the top end of the Engine Range, but the darn design (too much Plywood) is requiring the builder to add a lot of Nose Weight up front in order for it to balance. I'm hoping that if I move my RX Battery Pack behind the Firewall and scoot the Servos as far forward as I can get them then maybe I won't need to add that much weight in order for it to balance correctly.

The OS AX engine line is great. They run great, and last a long time! I am still using a 46 AX I bought fifteen years ago. They stay in tune and very rarely need any low speed needle adjustment. I own seven OS 55 ax engines, they all run great. They weigh the same as a 46 ax so I use a 55 AX in all .40 size planes. Here is a tip to make them last. When you find the Ideal needle valve setting after starting the engine go back one or two clicks to slightly richen the engine. Many flyers say you do not need after run oil. These are the guys who's engines need new bearings.Remove the glow plug and put three or four drops of oil in the cylander, then do the same in the carburator and turn over the engine with a starter to distribute oil. One old timer who insisted you do not need to use after run oil now uses it because my engines never fail!