My 912ULS was bought 2nd hand after being stripped and rebuilt, following an
accident
in a foreign airframe. I have no record of how long it operated since new
and my logbook starts at 220 hours, continuing from early 2014 and the
subsequent
8.5 years until now to log another 470 hours.
However I've become aware of gradually increasing oil consumption in the latter
years up until now, when I'm using 1.5 litres per 50 hours. As I recall,
originally
the consumption was less than 0.5 litre. There is a brown stain emanating
---From the exhaust and continuing under the port wing along the rear fuselage.
The most plausible explanation so far is that the valve stem oil seals have
stiffened
with age and should be replaced. This is something which I potentially
could do, having previously removed a cylinder head and lapped the valves,
resulting
in fully restored compression for over 150 hours. All 4 cylinders are within
3 psi of each other to this day and the engine performs as well as ever.
There are no other oil leaks from the engine and the breather collection pot
barely
fills at all. The spark plugs show no signs of oiliness. But I'm contemplating
that I might eventually remove all 4 heads and give them to an expert for
a proper refurbishment, once it reaches a point where I don't want to see the
brown streak on the port side any longer.
So to the point of this email. I definitely have no intention of removing the
cylinders
and pistons to check oil rings. Why? Because to the best of my knowledge
the Rotax 912 engines are very high quality, to the extent that I've never
read nor heard of cylinders, pistons and rings being badly worn with barely 700
hours of operation. I'm very willing to "take the chance" that only the cylinder
heads need refurbishment. So unless I see scoring of a cylinder wall after
head removal, I'll "let sleeping dogs lie." No honing, etc.
If I'm wrong and the head refurbishment isn't enough to cure the oil problem,
then
it won't be too awful to remove everything and start again.
My question is whether anyone knows of excessive cylinder, piston or ring wear
in an engine with only 700 hours, not due to human error like using the wrong
oil or losing coolant, or anything that contradicts my faith in Rotax.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=507684#507684
|