RE: The Complete Saito Notes by Bill Robison
300TTDP
Adjustment/operation of the Saito FA-300TTDP engine.
Preparation:
Before we talk about settings, let’s check the installation. Set properly, this engine can suck three ounces of fuel per minute, so we want a tank with the large size hoses all the way down to the clunk. And the clunk drilled out to match. This needs to feed a tee, again with a large bore. From the tee medium hose can feed the two carbs, but make the two hoses as close to the same length as your can.
A better set up is using a tank with two clunks in it, and individual feed hoses for the two carbs. Again, make the two hoses as close to the same length as you can. With two clunks medium fuel line will do fine.
The Saito pump does not pump fuel, it pumps air to pressurize the tank. Depending on the age of your engine you could have either of two systems. The early type had a diaphragm pump mounted under the left cylinder cam box, the late one has what seem to be two breather nipples on the crank case. With either system roll the engine, you will feel air blowing from only one of the nipples. That nipple should have a hose going to the next part. You should also have what looks like a remote needle valve, with one extra nipple on it. This is the pressure regulator. Two of the nipples will be directly across from each other, and the third down on the side of the part the needle screws in. The first two are one from the pump or crankcase nipple, the other to the tank vent. Doesn’t matter which is which, they interchange. the third nipple is the bleed line, you can leave it open if you have the real pump, or if you are using the crank case nipple it is also the excess oil drain from the engine, run a hose out the bottom to keep the inside clean. The hose needs to be a minimum of 4” length to give the vent the restriction needed.
Addition to clarify plumbing -
First, fuel feed from the tank to the engine. Since the FA-300 can use up to three ounces of fuel per minute any restriction in the feed lines can make it go lean.
The ideal tank set-up is two separate clunks, one feeding each carb. Failing this, using only one clunk, it will have to be a large bore, and large fuel line should be used to a (again) large bore tee fitting. From the tee medium size line can be used.
The tank can be pressurized in either of two ways. First is the normal muffler pressure from the tap on one exhaust pipe, but the fuel needs of the twin carb engine make muffler pressure marginal. A better method is to use the “Pump” supplied with the engine.
The FA-300TTDP has two nipples on the crank case, one in the common position on the back plate, the other on the bottom of the bearing housing below the cam cases. The nipple on the back plate has a ball check in it, it will only allow air to enter the crank case. The forward nipple is the air outlet, and is also used for tank pressure.
Along with your engine you got a strange looking remote needle valve, strange because it has three nipples instead of the normal two. This is your tank pressure regulator. Using medium fuel hose connect the front nipple on the engine to the single nipple on one side of the regulator valve, the nipple directly opposite goes to the tank vent. The third nipple, the one down on the side, is used as the crank case vent. It should have a hose connected and led to the bottom of the plane.
End of addition –