I just got a new .46 FX and strapped it on this weekend to break it in. It started with ease but some problems followed. I noticed that there is fuel bubbling out of the end of the hose on the exhaust nipple to the silencer, even thugh I believe the hose is tight. Also where the silencer screws together, exhaust and fuel and seem to be leaking out. The bottom of the muffler is covered with slime, which I did not notice on my .40 LA.

Thre is also ALOT of air in the fuel line and the engine delays when giving it full throttle. Anyone know any remedies?

I would first find the source of the air in the fuel line. There should be no air visible in the line from the the needle valve to the carb.

The new engine should be run rich during break-in so you will see some fuel coming out of the muffler although it shouldn't leak out of the seam where the two halves are joined. Mine did and I removed the nut from the end of the muffler, tightened the screw and then replaced the nut. There *are* threads in back half of the muffler. The nut just 'locks' it.

Once these are taken care of, address the idle->full throttle hesitation issue with the low end needle valve adjustment outlined in the manual. The low end needle valve is inside the carb assembly and is adjusted with a screwdriver in the center of the throttle linkage.

Hope this helps.

I have a few things you can check.

It seems you have two problems; a fuel line related one and a muffler related one.

Muffler:
The bubbles you see are most likely oil that comes from the exhaust. They could be a sign that the pressure nipple on the muffler is leaking. Some (most?) nipples has a nut on the outside of the muffler that you can tighten. If not you could try heat-resistant glue or liquid gasket material.

There is a long bolt inside the muffler. Loosen the nut (rear end), tighten the screw (front end) and retighten the nut. The rear part of the muffler has threads that the bolt screws into, and the nut is just a locknut. Black oil is usually a sign of metal-to-metal vibration.

The slime on the bottom of the silencer is most likely oil and nothing to worry about. The amount of oil depends of what type of fuel you run and how the engine was run the last few seconds before it was shut down. Full throttle means more airspeed through the muffler, and less oil is left inside. You can see this "phenomenon" if you let it idle for while (minute or two) and give full throttle.

Bubbles in fuel line:
This is not good. It sounds like you have an air leak somewhere. It doesn't take a visible hole to cause a leak, some times you'll only see the hole if you take the fuel line off and stretch it. A general rule of thumb: If the problems are there regardless of fuel level in the tank, the problem is most likely on the fuel line between the tank and the engine. If the problems appear at half tank or below, the problem is usually the fuel line inside the tank or the tank cap. I would retighten the cap and check/replace the fuel line.

This is what I'd do.

I did see some very dark brown oil dripping out of the muffler afterwords, so that means that theres been vibration and i simplky need to tighten it? If so, could the screw or what not being loose be the ource of the oil on the outside of the muffler and air in the fuel line?

Dark oil is no biggie. That's just oil out of the combustion. The air leaks in the nipple are easy to fix. New tube or tighten nipple as said earlier in thread. Permatex Ultra Copper sealer works where the muffler halves come together (and on that nipple). First clean with alcohol, then apply a little bit. Tighten it and whipe off excess. Worked for me. The tank could have a leak in the stopper, fittings, or sliced tubing. Replace it all and see if the air in the supply line goes away. Your stopper may just be not tight enough. The hesitation is just like someone else said, your low end mix. That should be adjusted by an experienced pilot or you risk getting it too far out of wack. It will need a quarter to half turn to make it less rich (it's in the manual..see fuel mixture setting).

Joe