The Enya doesn't use muffler pressure like your other engine because the carb is small enough not to need it so just do as was said earlier about leaving that line from the tank open and hanging in the breeze . There's a swivelling flap on the side of the muffler which was used to give a small shot of fuel straight into the exhaust port for priming but that's not necessary so keep it closed all the time or it'll be a bit loud.

Your engine is either a 15-IV or a 15-V, for some reason they didn't change the model number for the later engine. Now for the important bit . Don't use normal RC fuel in the Enya or it won't last long. It has a cast iron piston which needs at least 20% oil and preferably all castor. Personally I'd use 25% all castor fuel. With the right fuel these are very tough engines and will last just about forever.