Flew new motor today and seemed to lack some power,  so what is the deal with the cone shaped piece inside the muffler by the pressure fitting?Is this part necessary to performance or does it just add weight and restrict the noise?

I'm assuming you're talking about the Galaxy. The LA .25 *should* be plenty of power. How much the the plane weigh ready to fly? Leave the cone in the muffler. If you take it out, power does not really increase but fuel usage does (I don't know why) and the run gets erratic.

The LA 25 breaks in very quickly. Usually just a few minuets run time will do it. After 3-4 tanks of gas it should settle in to some sweet runs.

I think it would be the same, Joe. However, I've never run a .40/.46LA with the OS muffler...but my Magnum XLS .36 thinks it's just dandy! The one thing I'd consider is opening up the exit spout...but I haven't done that, either. I figured that a .46 muffler on a .36 should flow enough already.

Scott, that .25LA will run fine after a half dozen tanks...but put the 9-4 APC on it until it's got a couple dozen runs. The 9-6 is too much load, and you're overheating it. Set it richer, let it buzz up some, and it'll be better. After it's
stabilized the needle setting (doesn't need to be leaned out every run or two) and fuel consumption, then get the 10-4 APC on it.  I still think the plastic backplates are a potential problem, and would like to see you replace it with an aluminum one from a .25FP or CNC unit from Curtis Shipp. If it starts but quits for no apparent reason...that's the reason...  Steve

I've used the OS 15, 25, and 40-size mufflers.  They do a great job of making the engine quiet without loss of power.  I do not believe that opening the exhaust orifice would increase power because it's not the ultimate limitation of power on these engines.

People change to tongue mufflers purely for mass reduction. 
If the plane come out nose heavy and you need tail weight, that's double trouble.  So you spend $25 and save 2-3 ounces.
On the other hand, if you need nose weight you have a free fix.

HI Scott,

The OS .25LA works best with the 9-4 or 10-4 APC it seems, as Steve said.  And it should be in a "wet 2" cycle.  Very, very consistent and and puts out more than enough power for its size.

Go up to the "members tab" and search for Curtis, his email addy is there in his profile.  I would post it but there are web crawlers (or some such) that just search for email addresses in posts on the internet to spam through.  I went to the page that the "D"'s start on.  He is there near the end of the "C"'s as Curtis Shipp.  He was logged on around 10:30pm on the 14th so he is around.  Outstanding back plates and very very easy to work with.  Highly recommended.

Big Bear