I'm a flying female who never took shop in high school. But i love rc planes. Have a Saito 100 in a Tiger 60. There is a lot of oil in the cowl 'area' after flying. Does the breather nipple drip out excess fuel, or does it just 'breathe'? Could there be a leak somewhere, and where would that likely occur? I've checked around the fuel tank, all foam is dry. Maybe this is just all normal?

You just need a piece fuel line on the vent to carry the excess lube below the fuse. No more than 3 or 4 inches though.

Due to the way most four strokes work such as the Saito 100 (ooh lovely engine) the fuel (and therefore oil) goes in at the top by the valves. But the bearings at the bottom need the oil in the fuel to run right.

The idea is therefore that the oil is "blown by" when the engine fires into the crank case part of the engine, then lubricates the bearings etc, and out through the breather nipple. The nipple also allows the piston to go up and down freely without trapping air in the crank case which would interfere with it.

As Hobbsy says, you can run some fuel line to direct it out of the cowl. I have mine going out by the exhause. What ever you do, don't block it up, or attach it to the pressure nipple on the exhaust.

oh yes, lovely engine.

I'll give it a try

I have heard the part of no longer than 2 to 3 inch's before. Don't recall reading that in any manual, and haven't had a problem with a vent line over 12". Any place to get information on that? Why the length limit for the vent line?

I believe it would have to do with how many times per second the air and whatever in the line has to change directions, a longer line would require more pumping effort by the piston.

Yes, but air has less friction than liquid I would think that the vent line could be much longer than the fuel lines without much problem. At full power the blowby seems to be a larger flow than the back and forth action of the piston. I say seems, obviously I have never measured it, just observing that the oil comes out readily at full power, but not much at all at idle.