Today's Message Index:
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1. 05:50 AM - loss of compression (Catz631@aol.com)
2. 07:12 AM - Re: loss of compression (Roger Lee)
3. 12:22 PM - Worn piston ring grooves (rparigor@suffolk.lib.ny.us)
4. 07:52 PM - Re: loss of compression (dashwood)
Message 1
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| Subject: | loss of compression |
Well, it has finally happened to me. I have read about this problem
happening to a few members and now I witnessed it.
My Kitfox had not flown in about two weeks so I decided to fly it
yesterday. I checked the oil quantity and of course it was below the dipstick (as
usually happens when the aircraft sits for a while) I started turning the prop
thru its normal ritual when I noticed one of the cylinders had no
compression. Great, now what do I do. Well, the tank had not "burped " so I
continued turning the prop and eventually the compression came back on the one
cylinder and I flew the aircraft. The engine performed fine.
I am assuming I had a stuck valve and it "unstuck" itself. I have been
using 87 auto fuel with no alcohol. No avgas has been in the engine. The 912 UL
has 210 hrs since new. The only thing I have done differently recently (I
know this is sacrilege) is added Marvel to the fuel, along with fuel
stabilizer. I have read and talked to people that have had this problem in the
912
and they have indicated that Marvel seemed to help with sticking valves and
that is why I started adding it to the fuel. I used it in my Pacer and prior
aircraft with no problems. I have had problems in the past with sticking
valves until I used the Marvel (specifically a Cessna 120 which ended up with a
stuck valve and bent pushrod)
My plan of attack now, is to try and rotate the prop every day whether I
fly or not in order to move the offending valve.
If this happens again and the compression loss does not "fix itself"
should I run the engine or not? Did the addition of Marvel loosen carbon
sticking it in the valve guide? Should I not use it? I personally think it probably
had no effect at all on the valve sticking.
Any ideas would be greatly appreciated. I know this has happened quite a
few times to other guys with there 912's. My oil temp has been running about
190-200 in cruise and coolant temp about 185.
Dick Maddux
Kitfox 4
912 UL
Milton,Fl
**************A Good Credit Score is 700 or Above. See yours in just 2 easy
steps!
=JulystepsfooterNO115)
Message 2
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| Subject: | Re: loss of compression |
Hi Dick,
Why do you think you have a stuck valve? Many Rotax engines will feel less compression
or none at all when they have sat a while and or they are cold. (I have
experienced the same thing. Run the engine like you normally would up to operating
temps and then after that see if it feels the same. My guess it will be
back to normal. If the plane has sat a while a lot of the oil has drained away
from the areas that help seal some of that compression, plus the cylinder walls
and pistons are not at their optimal diameter because they are cold and different
metals.
Go taxi it around or just park it and run it up to 4000 rpm on the ground to temp.
bet it goes back to normal.
I know some people swear by Marvel Mystery Oil and it may not cause an issue, but
it may not help either. No one really knows in a Rotax. We don't know for sure
if it may have a odd burn with one of the engine oils or leave a burnt deposit
where you really don't want it. We just don't know for sure. 5 million Rotax's
running out there and the majority don't use Marvel Mystery oil and they
have never had any issues and some are in the 3000 hr range. I'm not saying don't
use it, but more or less, why?
Sticky valves aren't very common and is usually caused by something we did to the
engine or didn't do. Using a good fuel has cleaners already in them.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Service Center
520-574-1080
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=256637#256637
Message 3
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| Subject: | Worn piston ring grooves |
I was looking at O-300 Continential torn apart at 600 hours since major
with brand new Superior cylinders and pistonswith low compression
and cracked crankcase.
Anyway 2 pistons had worn piston ring
groves where the portion near the end gap of the rings was about twice the
thickness of the rings???
Anyone ever have such a problem with
a Rotax 91X?
Anyone know what would cause such wear? (perhaps
wrong choke?)
Ron Parigoris
Message 4
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| Subject: | Re: loss of compression |
I may not be understanding your plane but if i had no oil on the dipstick i would
add some first before hand prop to ensure i didn't just pump air into the system
from an empty reservoir. ????
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=256720#256720
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