Just got this motor from a guy in Austrailia. As usual,
no box...no goodies, and no instructions. Never had one
of these O.S. pumped pattern motors, and need help
with the fuel hook-ups....

First....what's up with 2 fuel lines going to the carb ?

Here's the pump....4 lines.
In....OK
Out....OK
"S"....line goes to the carb below the needle valve.
"R" ...line I guess would go back to the tank.

Do I still need an open vent line, or is the tank
sealed....or do I still run pressure from the pipe.
I'm thinking I won't need the pipe pressure anymore,
but will the fuel stop flowing if the tank is not vented ?

But you don't have a sealed tank, it should be vented or else either the engine will quit or it will look like a crushed coke can at the end of the run. Run the line you would normally use for the muffler straight down to the bottom of the engine compartment below the fuse.

The two adjusting screws appear to be factory set,
and marked with blue paint. I wonder what is what,
if they need to be reset ? I promise I won't monkey
with them.

Does any one have some instructions for these engines
they could copy ?

http://www.osengines.com/manuals/pre...structions.pdf

....you DA' MAN. Thanks for the link. I really need to
know more about the tank and fuel-line set up. Did you
read in that link about how they (who are they, anyway)
want you to set the high speed needle ? Lean it out 'till
the rpm's drop....and richen it up one click. With a
non-ringed motor (heh heh heh)...."they" must be selling
pistons and liners....or they know something I don't.

Maybe when the thing unloads in the air, and the RPM"s
go up a thou....it somehow richens up to the point where
it gets "happy" ? I don't think so. I'm running a regular
61 RF now....and with a 12-8....at 11,400....that's all they
turn....period. (with a Mac's pipe)

Do any of your pumped .46's have the same 4 line deal ?

I have no pumped OS engines at all, actually.

Look for wingspan99...he was asking about the pipe set up for a VF-P in the "speed" forum, thread was "VXDF Pipe Questions" I think...maybe he has some instructions.

Thanks for the reply.....I'm gonna have to try the "brute
strength and ignorance" technique on this one I guess.

It doesn't look like everyone on the planet has experience
with these ones. I wonder what the actual difference is
between these motors, and the "Hanno's"....other than
the red anodized head, the fancy name, and the extra
money it cost's to get one.

It appears that the lower carb fuel line is a return line
for excessive fuel to the carb. It appears that the upper
adj. screw is for the fuel pressure. I don't know why it
has a hole in it....it looks like a M/C main-jet. The lower
"return line" marked "S" must tie into the "R" line as a
return line to the tank, and I'll guess that the lower adj.
screw regulates the amount of fuel going back to the
tank.

I will further assume that no pressure is needed from
the exhaust, and if the Laws of Physics still apply....the
tank will have to be vented to keep it from collapsing.

Whatcha' think.... :stupid:

I would think an atmosphere vent would be fine. I know on the Perry Pump they said not to run muffler pressure to the tank, but I did anyway after some strange fuel draw problems..worked great with muffler pressure on the tank.

But you ain't got a Perry Pump...somebody will have the answer about it.

I may have to go to the "Pattern Dept".

Patience, Grasshopper...

That big urn isn't that hot....is it ?

OK Dave, here's the skinny: You have the two silicone lines hooked up ok. One is to return to the pump excess fuel at times. The lower right hand nipple (in your picture) goes back to the fuel tank. The upper right nipple connects to your tank clunk line. You run this set up with no muffler pressure--just an open vent line. Set the needle valve like any other--just a shade on the rich side of wide open. I ran several of these engines in pattern. Still have one. They are strong and reliable. The Hanno is about the same thing, but the pump is less complicated.

What about them screws....no "touchy touchy" ? :stupid:

I have no idea-

I have one of these engines. A real powerhouse. Rated at 1.85 HP at 16000.High speed mix is normal start at 2-2.5 turns out . Low mix screw is the screw running in the slotted arm. Move 5 degrees at a time, in for lean out for rich . Big yellow paper says don.t touch screws on pump, send back to OS. This was a new engine!!. Engine tinkerer that I am. Idled too rich no matter where the idle screw was. Turned the lower pump screw 1/2 turn.ran fine ever since. Very reliable, powerful engine. Questions? Just ask. Glad to help.

The nipples on the carburetor are:

1--nearest the needle valve: from the "out" line of the pump. this is the fuel feed to the carb.

2--inboard and lower from the needle. This connects to the "S" nipple of the pump. This carries venturi vacuum to the regulator in the pump.

The "R" nipple on the pump returns excess fuel from the pump to the tank at low throttle settings. You want to have this line dump at the forward bottom of the tank.

The "IN" line--this is the fuel line from the tank to the engine. It attaches to the clunk line in the tank.

Proper setting of O.S. pumped engines involves setting the high-speed needle as lean as possible without detonation or RPM drop. LEAVE IT THERE! If you have good fuel, the lubrication will protect the engine. You may be able to richen slightly, depending upon how the enigne runs in the air.

If the idle mixture's too rich, and it's as rich as the adjustment screw will go, then the high-speed needle's too rich.

The upper screw on the pump adjusts the pump pressure. It is factory-set so that the high-speed needle's at peak RPM when it's one turn out.

The lower screw adjusts when the return line opens to return excess fuel to the tank.

No fuel is returned to the tank from the carburetor.

Hope this all helps.

....thank you for the help (I printed it out to save)...
but one question....why do they want the engine
leaned out to the enth degree ? Are they wanting to
wring out the last rev ?
I was with the understanding that these engines, as
well as the "Hanno's" were tuned for lower RPM's, and
bigger props for "pattern". And they were long stroke
motors, with less RPM's than the old FSR's.

What exactly is the advantage of these "pumpers",
and what are they designed to do....over and above
the standard "RF" motors. Aside from the advantage
of a CG mounted tank, and the non-tendancy to lean
out going verticle ?

Dave.

Dave,

The pump provides reliable fuel delivery to the carburetor, and also allows a larger venturi than straight suction will allow.

When the engine was developed, a .61 was the larges 2-stroke engine allowed in FAI pattern, which is what the "Hanno" engine was designed for. You wanted every scrap of power you could get out of the egnine/pipe combination.

With the O.S. Hanno pipe, and an APC 12x12 prop, we'd usually see static RPM around 9,600 or so. This is where the engine was designed to run.