OS MAX 55AX - I realize this is an RC engine but I am trying to get it set up use in an EXTRA 300S Fun Scale for the Nat's.  My problem is that the throttle has a dead spot where the engine quits.  It is a very narrow bad at about 1/3 open.  Less open and it idles great.  More open and it runs great.  Hit this spot and it loads up, sits fuel out the carb and quits.  I am slowing leaning the low speed needle but so far I have not been able to cure it. I have has similar problems with a ST 90.  The cure for it was a perry carb.  I will continue to fiddle with the needle settings to see if I can dial it in.  Right now I am using 10% caster/synthetic fuel.
Would more or less nitro help?
Does anyone know if this normal for the OS 55AX?

By the way this engine is small light and very powerfull.  I think it would make a great stunt engine.

                

Exactly how light is it, without muffler ?

According to Tower 14.29 oz W/O muffler.  Rated @ 1.75 HP @ 16 K RPM.  Of course all this is with a RC crab.  I am not into stunt so what do I know.

By the way it seems that the HS needle was my problem.  As a new engine I had it on the rich side.  When I leaned it out a little the dead spot went away.

        

Remove the bearings  ASAP and replace them with stainless steel ones from Boca Bearing. On the main, remove shields(if they exist), remove factory grease and lube with Mobil 1. On the front, remove the shield facing the engine internals and do the same.

My experience with this engine is from SPA R/C Pattern on a Dirty Birdy 60. Despite liberal use of afterrun and running it  dry after each session, the bearings rusted after 17 flights and the piston & liner were ruined.

It is a fine, powerful  motor overall and I recommend at least 15% Nitro with 18 % oil. The ideal oil ratio is 15% synthetic, 3% castor.
Run it bone dry after each session and  use lots of afterrun oil.