That's not off for a properly tuned (non racing ) engine.

The OS AX .55 should consume under .6 oz/min at WOT.

The muffler used has nothing to do with it, as it only has a minor impact on fuel consumption.

The engine does require re-tuning though, so it is conceivable that adjustments, etc. cause it to eat more fuel ( most of which goes UNBURNED out the muffler ) causing the decreased run time.

I just went through this with a new GMS .76.

With the engine out of tune ( new ) running rich, I got a wopping 5 minutes out of a 11oz tank at WOT.

After breaking in and re-tuning I now get 16-17 minutes on a 12oz tank at WOT. The engine is now consuming what it should.


GMS makes the engines for Tower, and the mufflers and carbs are identical.