[tom0187rc]

Greetings
OS crankcase vent Changes
Four Stroke vents out of crankcase to open vent to air.
Four Stroke Surpass vent to intake manifold
A Series no external vent uses as internal lube
V series vents out of crankcase to open air.
I always use after run oil and use the crankcase vent to force after run oil into the crankcase never had change a bear so far in 8 years.
I am interested in a A Series no vent , i was reading a review in rcuniverse on OS FS 110 and there was a reported bearing failure after 6 month using after run oil down the carb.
I was wondering if any guys have had this experience with A series engines, Also anyone know why OS has went back to open air vents leaking oil into your cowl.
Thanks Tom

[Cougar429]

If I remember correctly there was an internal passage to vent the crankcase into the intake passage. I agree this was not the best option as you were forced to feed any contaminants back into the motor. There was also the problem of cleaning it if it every became plugged.

The addition of after run oil is likely one of the best long term treatments and I could not second that recommendation any more strongly. The oil that comes in the fuel can't protect the internal metal parts against corrosion from the remaining nitro/moisture and the combustion byproducts that leaked past the rings. Since I got into this hobby back in the 80's I have made my own from a 50/50 mix of Dexron and Air Tool Oil, although in the last batch I added a metal conditioner I found that increases the film strength, (only negative is it is quite a bit thicker in the cold).

In a 4-stroke there is no direct connection between the carb and crankcase, (unless you consider my YS91) so no way for the afterrun oil to make it where it's most needed unless you force it there as you do or it leaks past the ring, (likely a minimal amount). In this case I think adding it through the carb would be kind of useless and you also run the risk of mechanical damage if you rotate the motor with any amount of force and there is a good chunk of oil in the cylinder.


Kind of secondary to your question, but I found a couple of things to minimize oil into the cowl. That vent line can be routed outside, but the diameter should be relatively large, (regular silicone fuel tubing does not work the best) and it's absolutely crucial that line be kept as short as possible to allow each case cycle to breathe. If too long a good portion simply pulsates back and forth and the case never gets purged.

[MikeCam]

I've only been doing this for 3 years and run omega 10% (bit of caster) and don't use ARO unless it's going away for the winter. Got tired of hard starting and ARO all over the plane.

Asked a fellow club member who went thru drums of fuel a season for years about ARO. He said he never used it. Always ran a fuel with some caster in it. Asked him how many bearings he has changed out in his 30 years of RC. His answer, 0, nada none. Caster does protect the internals and very well. I run OS 2 and 4 strokes and Saito's and have had to open some up (bearings not being the reason ) and they all look great inside. One thing I do is run the fuel out, all out. If your flipping your engine and it dies the first time and you put it away, well then you better use ARO. I use a starter and turn them over with igniter on for 20 seconds after the last cough. Sometimes it will spin for 10,15 seconds then run again for a few seconds, especially the 4 strokes, need to get every drop of unburned fuel out of the engine.

Tex Gehman is a very knowledgeable guy to have at your field, I'm a lucky SOB. LOL

[Cougar429]

Mike, your procedure is a good one to flush as much of the fuel out of the motor as possible. This is especially effective with 2-strokes.

Unfortunately yours is also not all that common a practice. Very rarely do I see anyone going through the bother of that extra effort, (on that note I also rarely see anyone adequately warm up their engine before poring on the coals, also just as important for engine life).

The other problem occurs after the engine is shut off and fuel tank drained. Inevitably there will be traces of fuel remaining in the tank and if the fuel line is left on or reconnected to the carb inlet you have just provided a new source of contamination. Movement, attitude of the craft and temp changes can cause fuel to flow back into the engine.

On your comment regarding the member who goes through that volume of fuel: I would likely expect good motor life since the times his engines remain stagnant between runs sounds extremely short. Again, from everyone I regularly see this is rarely the norm.

My worst case scenario and one I see to varying degrees, is where the motor is shut off with the transmitter, plane packed up at the end of the session and then brought home to hang in an environment open to the elements, (an unheated garage is an example). The temperature fluctuations create flow into and out of the engine, providing a new source of moisture.

[MikeCam]

You make some very good points Cougar!!!!!!