Running a 46 FX that has always been a good runner in a different application. On an OMP 47 Edge profile using a 12.25 x 3.75 APC, 10% Byrons fuel, OS A-3 plug. Probably a gallon or less of fuel through it. Runs half or so of an 8 oz tank great but later in flight it will start bogging down in high demand positions like going over top in knife edge loop or in extended knife edge flight. Acts like it is leaning out and will die if I don't get it back to more normal attitude. Have tried it all the way from dialed in sweet on ground to sending it up pretty fat and everywhere in between-same thing. Acts similar but not quite as bad with 11x5 APC. Only thing I can come up with is last half of tank isn't holding enough pressure?? Any ideas?? I'm about ready to take it off and go Saito 82 or OS 50 like my other profiles.

You may not have enough muffler pressure or there is something wrong with your tank

Jim

Tank checks out OK-no leaks. Any ways to increase tank pressure? Forgot to mention-it has a Tower muffler on it-maybe I could try the stock muffler?? Kicking myself for not at least thinking to try that before[:@]

Try the original muffler and see what you get?

The tower has great top end but fuel draw is not as good. The mixture goes leaner when at full power and you have to compensate for it.

Enjoy,

Jim

Ken,

Get rid of that OS A3 glow plug!
It was never intended for your engine (even though the manual does list it a suitable{???}).

The [link=http://www.os-engines.co.jp/english/line_up/plug/pluindex.htm]OS Japan site[/link], where they're made lists this plug as suitable only for engines smaller than .32 (and the .40LA) and for break-in...

Because you have to run this engine richer, to preclude detonation from this hot plug, it will not run well in the mid-range.

Check the muffler nipple and see if it the hole in it is clear. You may have to
drill it out a tad....I had one that was restricted.

FBD.

Could be a hole in the clunk line in the tank?

This will bleed air into the line. Try a nose up on 1/4 fuel.

Here is a suggestion for the tower muffler. As mine heats up, the joints seem to loosen up and allow the center tube to leak. I sealed mine up with high temp silicone. (just a thin coating) Since doing this, my OS 50 transitions much better and will provide unlimited vertical on my profile plane. Also check for leaks in the fuel line between the clunk and the cap. I had one with a bad pick up line, I would die when the fuel got below the leak. Took me a month to figure that one out.

If your not using a gasket between the muffler and engine you can be losing muffler pressure there also.