First 4 stroke/cycle engine - Extra Nipple!!!
 

Hi,

Just need some help ref my first 4 stroke engine…

With a 2-stroke (cycle) engine, you have 3 ‘lines’ coming from the fuel tank:

Line A – Fuel line feeding fuel to the carbuerettor
Line B – Line from the exhaust muffler to the fuel tank to pressurize the tank for even flow of fuel
Line C – ‘Filler’ line to fill the fuel tank with.

Problem is that on my Saito FA 40 special (20yrs old I think..) as well as the above there is a ‘nipple’ at the back of the engine at the bottom where the plate is to get to the insides of the engine.
The instructions tell me this is a ‘breather nipple’, my questions are:

1. Do I hook up all the fuel lines as you would a 2 stroke – and if so, what do I do with this ‘extra’ breather nipple?
2. In a full scale 4 stroke plane engine there is a bath of oil that lubricates the workings of the engine – how is this provided on a model plane 4 stroke engine?
3. I have some Model Technics Duraglow 5 which I normally use in my 2 stroke engines – could I use this in the 4 stroke?

Many Thanks

RE: First 4 stroke/cycle engine - Extra Nipple!!!
 

Just attach a piece of fuel line and let it hang free under the engine. In a 2-cycle engine, the crankcase is pressurized for proper fuel flow through the engine. In a 4-stroke, the crankcase is not under pressure, and needs a vent line. You'll get some oild drippage from the vent line, hence the reason for attaching a tube to channel the oil "overboard".

4-strokes get their lube from the oil in the fuel, just like a 2-stroke. Both synthetic and castor oil have a much higher flash point than nitro and methanol, so they don't burn with the fuel, but gets pushed past the piston ring, and seeps by the valves through the guides; the oil that makes it past the piston lubes the rod bearings and eventually gets to the crank bearings and up to the cam drive; it's this oil that eventually gets dumped through the breather vent.

You can use the same three-line system with a 4-stroke as well as a two stroke.

I am not familiar with Duraglow 5, can't answer that one. Saito recommends at least 17% oil, as a castor/synthetic blend, and saitos run well on up to 30% nitro content, although 15% is plenty for normal flying, and all-synthetic oil seems to work well. I'm using 15% nitro, all synthetic (17%) Cool Power in the 5 Saitos I own, and haven't had so much as a second's problem.

RE: First 4 stroke/cycle engine - Extra Nipple!!!
 

Assuming you are flying a scale plane , my bet is on the extra nipple is for a pump connection with a check valve to better pressurize the tank.

RE: First 4 stroke/cycle engine - Extra Nipple!!!
 

khodges is correct- the nipple in the backplate just needs a piece of fuel line to carry oil outside the airplane.

I am not familiar with the Duraglow plugs. My Saitos ( as well as my Magnum and OS four strokes) run well with either Fox Miracle Plugs or OS type F plugs. In general four strokes tend to use a hotter plug than many two strokes.

I concur with khodges fuel recommendations except that I prefer a bit of castor.

I hope you find your Sato as enjoyable as I have found mine.

jess