I have a OS .40 LA engine that the muffler leaks through the seam on the two halves. Is there anything I should do other then try to tighten? I have it pretty tight already. I have positioned the exhaust pipe to the down position. I have a OS .46 LA engine (new), can I swap that muffler while I wait for a new muffler, if needed?

When the engine heats up, your "tight" joint becomes "loose".

Get the engine going and HOT.

Shut it down, and promptly clean it off quickly so it's still warm.

Pull off the back and clean it. Apply some high temp gasket seal compont to the joint, put everything back together and apply Locktite Blue to the screw/nut holding the muffler in place.

Remember that the SCREW does all of the work, not the nut ( if I recall correctly on this muffler ).... the nut is merely a retainer.

Screw it down tight, but be careful not to strip anything... and let dry.

Yes, this is correct. Am I losing power because of this leak?

The INTAKE leak is not likely to be causing power problems, as you've probably tuned around the leak, in effect taking it into account... though it can have adverse effects.

However when combined with a rich fuel mixture, it can make the engine hard to shut down as you are experiencing.

I have one SuperTigre that air leaks SOOO badly around the throttle drum itself that I can completely close off the throttle and the engine will just keep running until the fuel runs out...

The engine runs fine in the air, but I have to go running after the plane to pinch off the fuel, and even then it can take 40-50 seconds to shut off once I pinch off the fuel line... ugh!

Carb!? The OP mentioned the muffler halves leaking. Be careful tightening that muffler bolt since it will break if overtightened. About all you can do to stop the leaking is to apply RTV to the joint after cleaning it very well.

"Carb!? The OP mentioned the muffler halves leaking."

Carb? You must be mistaken, look again!

Yeah I meant Muffler... I was thinking about the carb leak as I typed... ugh.

I've used RTV sealant to solve the same problem. Make sure you get the high temp stuff. And it's a little messy to work with, so punch a very small hole in the tube and be neat with it. It works very well once dried.

High temperature silicone, the red one sold in tubes (dental paste-like) (by Loctite, I believe).
Easy find at Wal-Mart.

Never a leak; I even use it for the joint engine-muffler with no gasket.
No need for strong forces, just clean any excess after applying it.
Easy disassembly as well.

Now, some stains will come from the return flow of the carburetor.
The air-fuel mix goes into the nozzle while the engine breathes, and then a little of it goes out, which ends up over the hot surface of the engine and muffler, creating stains.
Hot water with some dishwasher powder will clean your muffler (do not expose it for too long).

I believe the muffler leaks do not affect performance of the engine; and yes, you can use the muffler from the 0.46.

Regards!

I had to do this same thing with my OS46fx muffler. I was told to apply the RTV and let it setup before tighting the screw down. That way it forms a gaskett, Then tighten it up and you should be fine. My works great now.

will the leak dosn't bother me that much. i just coat it with JB weld and re assemble it.

What bothers more than then the leak is...the back half will take on a flight path of it's own during flight.
i got lucky and found mind. I found other's mufflers too while searching for mine.lol

i managed to get a hold of some metric nuts with star washers. Then I double nutted it. then I put JB weld
on the threads behind the nut to prevent the nuts from vibrating loose.

Thanks for the help guys.

OS loves it when you overtighten the screw. This is what causes them to snap and then they get to sell you a new muffler. Just snug them down and don't worry about a little leak. Sheesh.

That is why God created "Tap and Die" sets!

To keep you from having to buy new mufflers.