Today's Message Index:
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1. 04:11 AM - Re: Fuel in oil 912ULS (Thom Riddle)
2. 04:56 AM - Re: Rotax 2 stroke (Catz631@aol.com)
3. 06:34 AM - Re: Rotax 2 stroke (lucien)
4. 09:25 AM - Re: Fuel in oil 912ULS (rampil)
5. 09:41 AM - Re: Fuel in oil 912ULS ()
6. 10:10 PM - Re: Fuel in oil 912ULS (K Dilks)
Message 1
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| Subject: | Re: Fuel in oil 912ULS |
Peter,
I think of only two ways that fuel could get into the oil supply.
1)The engine is running so rich that there is raw fuel going into the combustion
chambers and mixing into the oil on the cylinder walls.
2) You clean the oil tank with fuel and don't drain it and let it dry completely
before refilling with fuel.
If there is any other way, it does not come to mind.
--------
Thom Riddle
Buffalo, NY
http://riddletr.googlepages.com/sportpilot-cfi
http://riddletr.googlepages.com/a%26pmechanix
A complex system that works is invariably found to have evolved from a simple system
that works.
- John Gaule
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Message 2
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| Subject: | Re: Rotax 2 stroke |
LS,
Thank you so much for your tips !!!! I will print this page and pass it to
the guys today. They are having so much fun with the plane and I don't want
them to ruin their day by having to plant the aircraft in a field with an
engine failure ! I remember my old two stroke SAAB had a "free wheeling"
devicethat disengaged the engine when you coasted with your foot off the pedal.
Now I remember what it was for.
Dick Maddux
Milton,Fl
**************Looking for love this summer? Find it now on AOL Personals.
Message 3
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| Subject: | Re: Rotax 2 stroke |
Dick Maddux wrote:
> LS,
> Thank you so much for your tips !!!! I will print this page and pass it to
the guys today. They are having so much fun with the plane and I don't want them
to ruin their day by having to plant the aircraft in a field with an engine
failure ! I remember my old two stroke SAAB had a "free wheeling" devicethat
disengaged the engine when you coasted with your foot off the pedal. Now I remember
what it was for.
>
Yep - the rotax 2-strokes aren't among those that just quit or sieze for no reason,
so you can expect lots of hours and hours with just fuel/oil and flying with
them and very little if any trouble.
A couple other things:
- The CHT figures for the air-cooled motors in the 2-stroke manuals are wrong,
off by almost 100F hot. The correct operating range is more like 280-330F and
I'd call 350F the max. The 503 when broken-in runs around 300F normally, the 447
around 330 or so. The 447 will hit 350F in a climb easy but the 503 takes effort
to get that hot.
- the most common installation error is too long of a pulse line, the line running
from the pulse output on the motor to the pneumatic pump. No longer than a
foot and preferably 10" or less is what you want. If this line is too long, no
matter what it's made of, the pump won't be driven enough to pump with full
effectiveness. You can get totally mysterious fuel starvation events when this
line is too long.
- the only weakness on the 2-strokes is the crank seals. They start to leak after
about 50 to 60 hours, so this requires regular inspection. When you start getting
the black fluid collecting under the fan housing, it's time to start planning
a teardown/reseal....
LS
--------
LS
Titan II SS
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Message 4
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| Subject: | Re: Fuel in oil 912ULS |
I don't know if 1% fuel contamination is actually a problem or outside
the expected range for Rotax 9xx. It would seem an inconsequential
amount in terms of physical dilution of oil and reducing lubrication but
I have no idea as to whether it is relevant chemically.
Having an oil thermostat might treat the symptom, but as Thom
said the common way gas gets into oil is via leaky rings. The
first step in diagnosis would be a compression test to test the rings.
It is a required component of the annual inspection anyway.
Rotax advises that the compression test should be performed when the
engine is close to it usual warm operating temperature so that the rings,
cylinders and pistons are in expanded thermal equilibrium.
(I tried my engine cold and it tested fine, but others recently observed
that their engine leak mightily when cold)
Ira
(in the midst of my 5yr annual)
--------
Ira N224XS
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Message 5
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| Subject: | Re: Fuel in oil 912ULS |
Check the fuel pump Diaphram, if its weeping it can allow fuel to enter the gearbox/engine
regards
ivor
---- Peter Thomson <peterlthomson@gmail.com> wrote:
> I have found my oil analyses consistently show 1.2-1.5% fuel in the oil
> sample.
>
> Other oil properties (Shell Advance Ultra full synthetic, changed at 50 hrs
> on
> unleaded gas) are fine. Engine runs quite cool, but no moisture in oil.
>
> Any experiences here ?
>
> Peter
> Zenair CH701SP
> Rotax 912 ULS 380 hrs since new
> OIl analysis by Blackstone
Message 6
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| Subject: | Re: Fuel in oil 912ULS |
The fuel dilution is a feature of using blow by gas to return the oil to the oil
tank, there will always be some unburnt fuel in this. The designers take this
into consideration so hence the need to get the oil temp up to evaporate the
contamination out of the oil.
1% is ok but if you know you are running cool then do something about it. Long
runs at low power / idle will accelerate the dilution situation. Worst case is
when folks fill up with Jerry cans that have a small amount of diesel fuel ,
this goes strait to the crank case and in worst cases will increase the volume
seen in the oil tank.
Kev
--------
Austria .............
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