Today's Message Index:
----------------------
1. 05:51 AM - Re: Re: 582 compression (Noel Loveys)
2. 06:03 AM - Re: Rotax 912 UL (Catz631@aol.com)
3. 08:18 AM - Re: Re: 582 compression (Dave)
4. 11:42 AM - Re: Re: 582 compression (Noel Loveys)
Message 1
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| Subject: | Re: 582 compression |
I haven't done a differential test on a 4 stroke Rotax engine yet... but..
on the lycomings sometimes you will have to jiggle the prop a bit to get the
valves to seat. (that's what the boss said) That is when the prop can
really get away from you! My idea is if the valve train is clean you won't
need to jiggle. I can see where if you are running a geared nose the torque
produced will be multiplied and the accuracy of the TDC will be very narrow.
Noel
-----Original Message-----
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Roger Lee
Sent: Friday, August 01, 2008 4:45 PM
Subject: RotaxEngines-List: Re: 582 compression
Hi Guys,
Everybody has certainly good advice. There are two test. One is the static
test, where you turn the engine over and just read its top pressure.
I am not sure what the 582 static pressure is supposed to be. The static
pressures on the 912 typically run between 140-175psi depending on which
engine you have. The other test is the differential test. You need a
differential tester with a master orifice size of .040. You indeed do find
the top dead center of each piston you test. You can put your finger over
the hole and you should at some point during the prop rotation feel the
pressure coming out. When it starts to suck on your finger then you are a
little too far. TDC is where the pressure and the sucking stop. You can use
a piece of plastic to insert in the spark plug hole to check TDC also. For
the 912uls your compressor side of the gage should be 87 psi and if you are
right at TDC the guy holding the prop won't have much work to do, but heaven
forbid you are too far either way. The pressure will want to rip the prop
out of his hands. The lowest number you want to see on this test is 65psi.
You don't want a 25% drop.!
Then some maintenance needs to be done. If you are a little too far
either way on TDC you may hear some air out of the exhaust or the carbs. If
you are right on TDC you should be able to take the oil cap off and slightly
hear some air escaping. This is normal. Some air, I didn't say all the air.
I just did two annuals and pressure test. One 912uls had 100 hrs. the other
had 200 hrs. The readings were 86/84psi. They had a leak down of only 2 psi.
This is very good.
The 582 has steel cylinder inserts and aluminum pistons. These metals heat
up at different rates. Run a 582 from a cold start in the morning and don't
warm it up you could end up with a cold seizer. This engine needs to be
warmed up before running it hard. The 912 is totally different.
Before you do either test you have to have an engine at or about it's
operating temps for good accurate readings.
--------
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=196049#196049
Message 2
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| Subject: | Re: Rotax 912 UL |
I changed out my "P" leads on my 912UL and that seems to have solved the
problem with the roughness and bad drop on one mag.The prior "p" lead wiring had
both wires (unshielded) running in a blue shielded coax type cable which was
grounded on one end only. The manual calls for each "P" lead wire to be shielded
and grounded on both ends (which is what I installed) This plane has been
running since 2002 with the old set up (I bought the plane) and the problem has
just now developed? I couldn't find any breaks that were grounding the wires
but then again you can't see or feel inside the cable and the ohm meter check
was fine.
The only other problem I have is now my tach needle sharply spikes upward
then back down periodically during the engine run.It was steady as a rock prior
to my removal of the starter switch and replacing the "P" leads. The tach gets
its' power from the starter switch (the type with L,R,Start) so maybe I have
a bad connection there or at the plug connecting to the tach trigger coil.
Anyone ever have this problem?
I am thinking about installing Velcro as fasteners for my cowl. I have had
the cowling off so many times to work on this engine that my dzus fasteners
are about worn out. I am glad that I am retired and have a hanger to work on the
airplane otherwise, I would have to put it on static display in a museum. It
is mainly the engine that requires the work. I only have 175 hrs tt on the
engine. The airframe has been great. I envy you guys that work very little on
your planes and I don't know how you do it. I guess the secret is to buy it new.
In reality though,I have been doing a lot of improvements to it as it is a
mid 90's engine and needed it.(new hoses, proper oil line fittings,carb
cables,carb sync,etc.) Sure does run smooth though.However I don't think I will
fly
it to my cabin in North Carolina as I did my Piper Pacer. I still don't trust
the engine as I did my Lyc or Cont on my other aircraft. Again, thanks for all
your replies!
Dick Maddux
Kitfox 4-1200
Rotax 912UL
Pensacola,Fl
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Message 3
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| Subject: | Re: 582 compression |
I'm sure others are more knowledgable in this procedure than I, but I have
been dealing with two stokes for many years and would like to throw a very
large caution out there. If you happen to apply 70 or 80 PSI to a two stroke
engine, and for any reason the crankcase seals either by lower the piston
for a 503 or if the rotary valve covers the port in the 582, then I would
very much expect to blow the seals on the crankshaft. The seals cannot be
replaced on the inner sides of the crank without dissassembly and
reassembled cranks are not supposed to be used on aircraft according to
Rotax. Just a thought.
Do not archive
Message 4
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| Subject: | Re: 582 compression |
That's just another couple of reasons to keep the cylinder under test at
TDC. If there is a leak through the rings any pressure will be released
through the base into the exhaust port.
Noel
-----Original Message-----
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Dave
Sent: Saturday, August 02, 2008 12:46 PM
Subject: Re: RotaxEngines-List: Re: 582 compression
I'm sure others are more knowledgable in this procedure than I, but I have
been dealing with two stokes for many years and would like to throw a very
large caution out there. If you happen to apply 70 or 80 PSI to a two stroke
engine, and for any reason the crankcase seals either by lower the piston
for a 503 or if the rotary valve covers the port in the 582, then I would
very much expect to blow the seals on the crankshaft. The seals cannot be
replaced on the inner sides of the crank without dissassembly and
reassembled cranks are not supposed to be used on aircraft according to
Rotax. Just a thought.
Do not archive
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