OS 70 Ultimate 2 4 stroke

I have been running this thing on the carb on the bench maost of the day (on and off). It is certainly no Saito 72. It spins a lot better, and appears to make a lot more power.

Starts good. Pump works good (even from a gallon tank).

Screams like a banshee...

I have a OS 70 Surpass in a 60 size RC ship. It has unlimited verticle. I run a 13-8 prop. Also using a Perry Pump Oscillating or vibrating type. I like the pump because it pulls fuel from the tank and then pumps to the engine. As opposed to pressurizing the tank. I have seen many pressurized tanks leak inside the plane and not be found until the plane was ruined. I call this motor my workhorse as it is dependable and has power to spare. The new ones are probably better. I have no experience with 4-strokes on u/c ships....yet!

'zilla,

I've looked at these. Almost bought one a couple of weeks ago. I do like the pump. Looks like it could be a killer. And it's not obsenely heavy.

>I have been running this thing on the carb on the bench
>maost of the day (on and off). It is certainly no Saito 72.
> It spins a lot better, and appears to make a lot more
>power.
>
>Starts good. Pump works good (even from a gallon tank).
>
>Screams like a banshee...

The OS web page says, "The most important new innovation found on the FS-70 Ultimate is a Pump System incorporated on the back plate. It pressurizes the fuel tank for constant fuel delivery at any attitude."

How is this different than crankcase pressure from a 2 stroke? Is it really pressure regulated and remains constant?

>How is this different than crankcase pressure from a 2
>stroke? Is it really pressure regulated and remains
>constant?

The pump system is as follows:
1. Crankcase pressure with check valve. This pressurizes the tank to about 6 to 10 psi.
2. Pump? The outlet for the fuel comes from a "pump" in the backplate. This is to assure constant volume to the engine, same as a Perry pump.
3. Regulator. There appears to be copy of a Cline regulator built into the side of the carb. My theory at this point is this regulator is what necessitates the high tank pressure, as the Cline also requires high initial pressures to function correctly. The Cline operates on a principle that the engine is only supplied with as much fuel as the carb "draws".

The carb with regulator is coming off tonight, making way for the new UHP manifold. Hopefully, without the regulator the high tank pressure will not be necessary, as I have no love of pressure tanks.

If that does not work, I guess we will make a new backplate with a Perry pump, as I know that works beautifully.