Don't I need some type of vent?

[Maxists The Baddist]

Using an OS 90 with pump and no muffler preasure, won't that leave the fuel tank sealed.

[Neriyah]

You need to have a vent line too. Just use the one you'd use for muffler pressure and run it down to below the main tank. This should keep the fuel in even when inverted (and the engine will be sucking in air through that line which will keep the fuel in). Some claim you need to use check valve on it and other say never to use one since it will fail and/or cause inconsistent runs. I don't use one and have never had any problems.

[Maxists The Baddist]

Thanks. I kinda wish I got the non-pumped. This sounds like it could get messy.

[Neriyah]

I'm very happy with mine. No corrosive gasses to rot your fuel lines and engine runs like a charm (well after 2-3 gallons it runs like a charm :)) And don't worry no fuel will spill out of it even if some ppl find it hard to believe.

[Maxists The Baddist]

Thanks for the help Neriyah. I do find it hard to believe fuel won't run out, but I am going to try it.

[DavidH]

The fuel will not run out the vent line. The vent line needs a loop above the tank when the heli is upright. If you know what a trap looks like in a sink drain, that is what the vent line needs to look like. Hook the fuel tubing to the vent, then run it 3-4 inches above the top of the tank, loop it over and run it down beside the tank and let the open end be below the bottom of the tank.
Fuel will not run out even when inverted. One of the reasons is the pump is pulling fuel from the tank, so the vent line is intaking air and fuel can not run out of it.

David