Plumbing for an inverted OS46FX
 

Many of the ARF's now out call for the engine to be mounted inverted. I have an OS46FX mounted inverted in a kit and I have trouble with vapor lock.

I plumbed it using one tube to the Muffler, one to the Carb and one to a filler that I have mounted in the side.

When I use the filler, Fuel eventually goes into the muffler when the tank is full :confused: and causes the vapor lock. Any ideas on what to do about this would be greatly appreicated.

Plumbing for an inverted OS46FX
 

Disconnect the pressure (muffler) line when filling. When fuel comes out that line, you know it's full. This is standard procedure regardless of the position of your engine.

Plumbing for an inverted OS46FX
 

I am with you there. Have done this on many planes, but the neat cowl I have prevents me from reaching the connetion to the muffler.

So, do you think I have only once choice? Cut the cowl so I can reach the connction?

Plumbing for an inverted OS46FX
 

About your only other option would be to hold it pointing straight up while fueling so that once it is full, the fuel will immediately start to run out of the muffler and not build up in there.

Plumbing for an inverted OS46FX
 

On some of my planes I've drilled two holes outside the cowl then threaded the fuel line through the hole then cut the fuel line and added a coupling or filter.Now the line is easy to access for fueling or defueling

Plumbing for an inverted OS46FX
 

Put a tee in the line going to the muffler with the stem of the 'T' pointing down just like it is when it's typed here. The top of the tee will go to the muffler and tank respectively... Add a short piece of tubing onto the stem and let it hang down below the cowl. When fueling, the overflow will run out of the downspout and never get to the muffler. Plug the downspout before running or you'll have no muffler pressure.
It works best if the entire vent line dips down kinda like the trap under a sink with the 'T' at the lowest point. That way, you'll get NO fuel in the muffler.