smoke from engine

Hello all,

This afternoon I made a flight with my Safari 30 minutes and after
refuelling I started again the engine and there was a lot of smoke coming
from the exaust. very impressif. A guy from the local air club told me this
could come from one valve not correctly positionned whenn the engine was
stopped.We discover later that there was plenty of oil in the exaust svifel
.. Some oil was even leaking on the heating duct. Finaly the smoke disapear
after 2 or 3 minutes running.
Any body has an idea of what exactly happened? The engine is from a crashed
r22 and has 700 hours since new. All gages oil pressure temperature cilender
head are ok .All comments welcome

Claude

lescure wrote:
Hello all,

This afternoon I made a flight with my Safari 30 minutes and after
refuelling I started again the engine and there was a lot of smoke coming
from the exaust. very impressif. A guy from the local air club told me this
could come from one valve not correctly positionned whenn the engine was
stopped.We discover later that there was plenty of oil in the exaust svifel
. Some oil was even leaking on the heating duct. Finaly the smoke disapear
after 2 or 3 minutes running.
Any body has an idea of what exactly happened? The engine is from a crashed
r22 and has 700 hours since new. All gages oil pressure temperature cilender
head are ok .All comments welcome

I don't have any experience in aircraft piston engines, but I've seen
car piston engines do this when the valve seals get old. A little
bit of oil leaks past them and is quickly burned off as soon as the
hot engine is restarted.

Ideally it should not do it at all, and it will get worse, not better
if you have no work done to correct it.

The quantity of oil you describe is surprising, but maybe that has to
do with the position the engine came to rest on shutdown. Have you
checked for that on subsequent shutdowns and hot restarts? Also,
what is the engine's recent oil consumption?

You can take a little comfort in that only a few drops of oil can
make impressive size puffs of smoke.

Any body has an idea of what exactly happened? The engine is from a crashed
r22 and has 700 hours since new. All gages oil pressure temperature cilender
head are ok .All comments welcome

Claude,

One of the recurring inspection on your engine is the valve guide to
valve stem clearance. The rocker cover is removed and the valve stem
is moved back and forth to measure the movement. There is a go, no-go
limit that I can't think of off the top of my head. Excessive
clearance can allow oil to leak into the combustion chamber. One
associated issue is if it builds up with deposits from burnt oil it
can cause the valve to stick. This is bad! I would suggest getting
the AD's and service bulletins for the R22 and looking for the valve
guide to valve stem clearance test to start with. I can't remember if
it was SB or AD. One other slim possibility is a crankcase breather
problem causing the crankcase to build pressure, but this is visible
by other oil leaks normally. The bottom line, get it checked out.

Regards,

Eric D

AD's and service bulletins for the R22 and looking for the valve
guide to valve stem clearance test to start with. I can't remember if
it was SB or AD
It's a service bulletin. Go to the Lycoming site and they will have it there
for a free download, however, I don't think that's the problem. I seen many
Lycs that didn't pass the wobble test and none of them smoked (just siezed
valves and bent pushrods).
You also need to buy an expensive tool to check the wobble.

I would crank the engine (after it has set at least overnight) as if you were
going to start it, leave the mixture lean, then I would pull the plugs and see
which cylinder is the offender by looking for oil fouled plugs.

If you have a worn valve guide you can usually see it. The excessive clearance
between the stem and guide doesn't allow the valve to cool enough and it
generally cooks the oil around the spring and keepers on the exhaust valve.
Don't compare intake to exhaust visually. The intake runs a whole bunch cooler.
Compare cylinder to cylinder, exhaust to exhaust

Thank you all
Stuart Fields a very experienced Safari builder and owner found the
solution:

Oil smoke. I found a depression in the crankcase below the cylinder(I think
it was #4) that held a couple of tablespoons of oil. It can bleed down into
the cylinder. I drilled a 1/4" hole in the bottom of the depression to
drain this oil down into the crankcase. This oil does not collect in a
horizontal mounted engine. This mod stopped my engine from doing the smoky
start like the one being described here. The only way I found the
depression was searching for the problem, I pulled the cylinder suspecting
valve troubles. When I found no valve problem, I continued looking until I
found the puddle of oil setting there. Apparently it is the only spot in
the crankcase to collect the oil in such a manner as to make it avalible to
get down into the cylinder and out thru the exhaust.
Stu

Hey guys: I went thru some of this thinking I had a valve problem. I did
compressions tests and plugged the intake and exhausts and pressurized with
the valves open expecting to hear air coming up around the valve stems into
the rocker box area. Nope. Not until I drilled that little 1/4" hole, (I
was told by a "Grey Bearded A&P" to make it a 1/2" hole, but I chickened
out, then the oil smoking stopped. I'm sure that this phenomena doesn't
occur with a horizontally mounted engine.
S.Fields

"Gyroplanes" wrote in message
...
AD's and service bulletins for the R22 and looking for the valve
guide to valve stem clearance test to start with. I can't remember if
it was SB or AD
It's a service bulletin. Go to the Lycoming site and they will have it
there
for a free download, however, I don't think that's the problem. I seen
many
Lycs that didn't pass the wobble test and none of them smoked (just siezed
valves and bent pushrods).
You also need to buy an expensive tool to check the wobble.

I would crank the engine (after it has set at least overnight) as if you
were
going to start it, leave the mixture lean, then I would pull the plugs and
see
which cylinder is the offender by looking for oil fouled plugs.

If you have a worn valve guide you can usually see it. The excessive
clearance
between the stem and guide doesn't allow the valve to cool enough and it
generally cooks the oil around the spring and keepers on the exhaust
valve.
Don't compare intake to exhaust visually. The intake runs a whole bunch
cooler.
Compare cylinder to cylinder, exhaust to exhaust