Today's Message Index:
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1. 05:33 AM - #1 cylinder plugs are black (Thom Riddle)
2. 09:53 AM - CHT J thermocouple replacement for Rotax 912ULS (Martin Pohl)
3. 10:05 AM - Re: #1 cylinder plugs are black ()
Message 1
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| Subject: | #1 cylinder plugs are black |
--> RotaxEngines-List message posted by: Thom Riddle <jtriddle@adelphia.net>
During our annual inspection we removed all spark plugs, cleaned and
gapped them before re-installing them. They had about 100 hours on them
with virtually no wear and all the plugs except for both plugs in #1
cylinder were perfectly colored. Both plugs in #1 cylinder were black.
We also balanced the carbs and have sense flown the airplane about 5
hours.
A couple days ago we removed plugs from #1 and #3 cylinder to see if
the black sooty condition had improved. #1 plugs (both) again are black
and sooty while #3 plugs are fine.
Engine seems to run fine and smooth at all power settings. Apparently,
#1 cylinder is running rich but both it and #3, which is burning clean,
are fed from the same caburetor.
Any ideas as to what's going on?
Thom in Buffalo
Message 2
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| Subject: | CHT J thermocouple replacement for Rotax 912ULS |
--> RotaxEngines-List message posted by: "Martin Pohl" <mpohl@pohltec.ch>
I am trying to find a replacement for the standard Rotax 912ULS CHT sensors.
Does anybody know what kind of metric thread is used on the Rotax 912 CHT sensors?
Someone (Tony, EuropeKiwi) is using Westach CHT J thermocouples. Does anybody
know what P/N they have?
Thx, Martin
--------
Martin Pohl
Zodiac XL QBK
8645 Jona, Switzerland
www.pohltec.ch/ZodiacXL
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=39605#39605
Message 3
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| Subject: | Re: #1 cylinder plugs are black |
--> RotaxEngines-List message posted by: <rparigor@suffolk.lib.ny.us>
Hello Thom
"#1 plugs (both) again are black and sooty while #3 plugs are fine. Any
ideas as to what's going on?"
Not in order just rattling:
****First off change the plugs. Unless you have access to a pressure
tester to make sure they are not snuffing out under pressure
****Make sure you have the proper heat range plugs! If the porcelain is
shorter, it will run cooler and could run black.
****You sure it is black from running rich, or could it be black from oil
fouling?? Perhaps run a compression test, that will not tell you if oil
ring leaks or valve stem seal, but if low hint to look further.
****Are you using Whacker Silicone based thermal conductive compound on
plug threads?
****You have a CHT and EGT to help diagnose problems?
****If you look up mixture check procedures for 914 at take off power,
they have you measure each cylinder for O2 content. They want a minimum
amount to be certain that things are not running too lean. Eastwood sells
such a tool, could be used to check for proper mixture at various throttle
settings as well.
****Make sure float bowl shows no signs of overflowing, check needle valve
and float look OK, clean carb while you are at it
****I am not certain on this one, but a restriction on exhaust is not a
good thing, make sure clear on that cylinder
****If it is only happening on 1 of the plugs in that cylinder, could be
besides a bad plug, faulty ignition pick up, coil, module or wires
****You getting cooling problems on that cylinder, like too hot or too
cool?
****MAKE SURE YOU HAVE PROPER HEAT RANGE OF PLUGS especial on black
cylinder
****If you could somehow get hold of a EGT put it in suspect cylinder. If
you turn off gas, you should not get a very severe rise, if you do then
too rich.
Try it with a good cylinder to see what normal is. Remember black could
be caused at many a throttle position. Choke motor when hot a very low
throttle opening which you know is rich, and see what rise is. Just be
very careful on purpose running lean like this above 50% power, do it just
to get peak then retard throttle and turn on fuel.
Had enough yet?
If not, what motor you have? How does it start? How does it start in cold?
How many hours? MoGas or 100LL? What is compression on 4 cylinders? Did
you install new length dipstick? What type of oil you running? You
checking oil properly where you do not have things overfilled? Is there
blue smoke coming out of exhaust, if 2 pipes, then the one with #1 upon
cold start up? How bout black smoke on cold start up? Is your oil pressure
excessive high, has it changed since you did not have black plugs?
Let us know how you make out
Ron Parigoris
Ron Parigoris
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