Today's Message Index:
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1. 04:54 AM - Re: 912UL turning backwards on shutdown (Malcolm Ferguson)
2. 05:47 AM - Re: 912UL turning backwards on shutdown (Catz631@aol.com)
3. 06:30 AM - Re: 912UL turning backwards on shutdown (Richard Girard)
4. 02:43 PM - Re: 912UL turning backwards on shutdown (Roger Lee)
5. 02:44 PM - Prop reversal (Victor Menkal)
Message 1
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| Subject: | Re: 912UL turning backwards on shutdown |
Dick, I had that problem. Engine would sometimes stop okay, sometimes
diesel, sometimes run backwards. Turned out to be a crook wire in the p
lead making a partial circuit. Very hit and mis. Now have my idle set
for 1200 rpm. Never idle this slow except when shutting down. I turn off
the mags seperately. Gives the smoothest shutdown, not the usual drum
full of bolts sound.
Malcolm Feguson
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| Subject: | Re: 912UL turning backwards on shutdown |
Dave,Richard,Scott,Noel,Ron,Roger....Holy Mackerel are you guys alive or
what? I certainly can't answer each one of you but you guys have certainly
come through with some great ideas!! (I apologize if I left anyone out.)
To answer some questions, I have been using auto fuel premium (no ethanol)
I went to premium because the run on occurred almost every time with
regular when the outside temp was hot. ( even though as you say Dave the 912UL
is
supposed to use regular)
I will lower the idle speed even further for shutdown purposes and turn
off the mags one at a time (with a pause) as you suggest Roger. That makes
sense and I have not been doing that. My idle speed is about 1700 rpm now.
I don't have a choke, only a primer. I might give it a squirt at shutdown
as you suggest Ron. Cooling fuel might stop this from happening. I will also
check the idle mixture as you say it might be on the lean side. Scott, you
brought up a good point on turning the fuel off. It makes sense that one
float bowl could go dry before the other causing an imbalance. I would be
willing to bet that that is why Rotax uses the ignition to stop the engine vs a
mixture or some sort of a fuel shutoff. No possibility of an imbalance that
way
You know the "water cleansing" of cylinders was brought up by a friend of
mine Ron. He too used to do that to get rid of carbon in the cylinders of
his bikes and cars and had great success. I have borescoped my cylinders and I
do have a small amount of carbon but not much. I will kept that in the back
of my mind. I suppose you could spray water into the inlets of each carb
simultaneously. However I do remember that we had water injection on the old
DC6 (C-118) I used to fly while in the Navy. It was disabled so we never used
it but as I recall it raised the compression and produced more power. It
was only to be used when you absolutely, positively had to get off the ground.
I believe a few jugs were blown so they disabled it.
As far as plugs go I have been using the standard recommended for the
912UL. I don't remember the number off hand. Any suggestions for a colder plug?
So here is the plan for shutdown:
(1) Fresh premium auto fuel (avgas if this doesn't work)
(2) reduce idle speed for shutdown purposes (1400 or so)
(3) turn off mags one at a time (shot of prime if necessary to cool
cylinders)
I generally don't have a problem in the winter. It is this horrible summer
heat that seems to bring it on. The engine temps at cruise (and idle) are
fine though. I am running about 185 CHT,195-200 Oil temp ,1300-1350 EGT on 95
degree days.
Sorry to be writing a novel here but early morning, good coffee, wife
still sleeping, makes for good times. Thanks again for all your help !!!
Dick Maddux
912UL
Milton,Fl
Message 3
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| Subject: | Re: 912UL turning backwards on shutdown |
Dick, When I was a kid with my first VW I used to visit with an old German
mechanic who had his own independent Porsche garage. He showed me a way to
decarbon. I've used it, it works. It will take two people to do it with a
912, one to spray, the other on the throttle. Mix 1 part kerosene in 3 parts
water in a spray bottle, you'll need two. Shake vigorously as you would oil
and vinegar dressing. Raise RPM of warm engine so it does not stall. Spray
into carbs. Watch color of exhaust, it will be blackish as the carbon comes
out, then light gray as you're just processing the water / kerosene mix.
You're done when engine idles normally after a good runup.
Rick Girard
On Mon, May 31, 2010 at 7:47 AM, <Catz631@aol.com> wrote:
> Dave,Richard,Scott,Noel,Ron,Roger....Holy Mackerel are you guys alive or
> what? I certainly can't answer each one of you but you guys have certainly
> come through with some great ideas!! (I apologize if I left anyone out.)
> To answer some questions, I have been using auto fuel premium (no ethanol)
> I went to premium because the run on occurred almost every time with regular
> when the outside temp was hot. ( even though as you say Dave the 912UL is
> supposed to use regular)
> I will lower the idle speed even further for shutdown purposes and turn
> off the mags one at a time (with a pause) as you suggest Roger. That makes
> sense and I have not been doing that. My idle speed is about 1700 rpm now.
> I don't have a choke, only a primer. I might give it a squirt at shutdown
> as you suggest Ron. Cooling fuel might stop this from happening. I will also
> check the idle mixture as you say it might be on the lean side. Scott, you
> brought up a good point on turning the fuel off. It makes sense that one
> float bowl could go dry before the other causing an imbalance. I would be
> willing to bet that that is why Rotax uses the ignition to stop the engine
> vs a mixture or some sort of a fuel shutoff. No possibility of an imbalance
> that way
> You know the "water cleansing" of cylinders was brought up by a friend of
> mine Ron. He too used to do that to get rid of carbon in the cylinders of
> his bikes and cars and had great success. I have borescoped my cylinders and
> I do have a small amount of carbon but not much. I will kept that in the
> back of my mind. I suppose you could spray water into the inlets of each
> carb simultaneously. However I do remember that we had water injection on
> the old DC6 (C-118) I used to fly while in the Navy. It was disabled so we
> never used it but as I recall it raised the compression and produced more
> power. It was only to be used when you absolutely, positively had to get off
> the ground. I believe a few jugs were blown so they disabled it.
> As far as plugs go I have been using the standard recommended for the
> 912UL. I don't remember the number off hand. Any suggestions for a colder
> plug?
>
> So here is the plan for shutdown:
> (1) Fresh premium auto fuel (avgas if this doesn't work)
> (2) reduce idle speed for shutdown purposes (1400 or so)
> (3) turn off mags one at a time (shot of prime if necessary to cool
> cylinders)
>
> I generally don't have a problem in the winter. It is this horrible
> summer heat that seems to bring it on. The engine temps at cruise (and idle)
> are fine though. I am running about 185 CHT,195-200 Oil temp ,1300-1350 EGT
> on 95 degree days.
> Sorry to be writing a novel here but early morning, good coffee, wife
> still sleeping, makes for good times. Thanks again for all your help !!!
>
> Dick Maddux
> 912UL
> Milton,Fl
>
> *
>
>
> *
>
>
Message 4
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| Subject: | Re: 912UL turning backwards on shutdown |
Hi Dick,
Unless you idle excessively then I would expect you to see black carbon coloring,
but not a substantial or thick build up. The black coating would be normal
especially if you have any time on the engine. If I remember your engine hours
you don't have that many. I just don't see this as a carbon issue.
--------
Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center
520-574-1080
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=299487#299487
Message 5
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Hi Dick. I think you may have identified one potential cause with your last
line regarding prop weight.
I do recall the instructors at my iRMT course cautioning against using a prop with
a high moment of inertia (as opposed to weight) as causing excessive wear
on the gear box and kicking the engine backwards on stop - start.
I dont have my line maintenance manuals or prop specs with me but I believe the
3 bladed warp drive is approximately 10,000 kgm2 and Rotax specifies no more
than 6,000 kg.cm2 for the current 912S (could be lower for your engine - gear
box combination). Please confirm these values with Rotax and Warp Drive specifications.
I think a quick search of service bulletins would give you the correct data regarding
mass moment of inertia. SB-912-042 R1 and SI-11-1991 is what I find
on my computer.
Cheers Vic
iRMT
Whitehorse Yukon
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