I have a OS 120 installed in a 4* 120 and am tiring to set up the engine and finally noticed that because of the pump I don't have any place to connect the fuel line that normally goes to the muffler. This line needs to be able to vent to the air so what to do? Just let it hang in the air or???
Ben

Ben,

On the pumped engine, you don't connect anything to the muffler. You will need to run a fuel tank vent that goes from the inside top of the tank and then exit through the bottom of the fuselage. Your tank will have three lines: Fuel pickup, return line, and vent line.

Thank you for your reply. You have unfortunately added to my dilemma. I only have two line coming out of the fuel tank area. I was going to use the vent line to fill the tank and be a vent like I do on my OS90's I use on my other planes. Can I still do that? Do I have to have a third line?
Thanks

I love these 4 cycle OS engines!!!

Ben

You need a third line on the O.S. Max FS-120 Surpass II because two lines are fuel feed and return line. You need a third line to allow air to get into the tank to replace the fuel that gets consumed.

There's no alternative.

If your engine is the FS-120 Surpass III, then you only need a fuel line and a vent line in the tank.

Heres a question for those guys who know and have flown the Giant Scale Top Flite P-51 ARF , I have the Real Flight Simulator on my PC , the P-51 on the sim appears to be the Top Flight giant scale model . On of the engine options is a 4 cycle OS 120 with an 18X6 prop ........This engine in the P-51 in this simulator seems much easier to fly than with the Super Tigre G 4500.

Is this any where close to accurate ,,,,,,,,,,,I don't think the Top Flight instructions mentions a 4 cycle this small................

But the simulator combination works well?????????????.........................Any comments on engine size for the real model is welcome......................ZDS