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markdonahue(at)earthlink.
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 Posted: Mon Jun 25, 2007 9:25 pm Post subject: 912 starting problems |
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Kitfox model IV with a 912 UL
Does anyone have some thoughts for me as to how to make my engine start more easily.
Engine runs fine after starting. Battery is good and turns over briskly. Choke pulls to the stop. Throttle on idle. Have checked carbs and jets all are clean and all seems clear. If I add a bit of gas at the filter it will fire. Seems like its carb related. Spark seems weak, but have changed ignition wires and no change. And again it runs strong. I have had the carbs rebuilt at Lockwood, but that was 3 years ago, but it didnt seem to make any difference. Any thoughts anyone.
I have 790 hours on the engine.
Mark Donahue
[quote][b]
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pjeffers(at)talktalk.net
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| Posted: Mon Jun 25, 2007 11:03 pm Post subject: 912 starting problems |
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Hi Mark
Probably a slipping sprag clutch. Quite a common problem with older 912’s. There is also a modified larger starter motor available from Rotax which will prevent future problems with the clutch.
Just a thought!!
Pete Jeffers
From: owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of markdonahue
Sent: 26 June 2007 06:24
To: rotaxengines-list(at)matronics.com
Subject: 912 starting problems
Kitfox model IV with a 912 UL
Does anyone have some thoughts for me as to how to make my engine start more easily.
Engine runs fine after starting. Battery is good and turns over briskly. Choke pulls to the stop. Throttle on idle. Have checked carbs and jets all are clean and all seems clear. If I add a bit of gas at the filter it will fire. Seems like its carb related. Spark seems weak, but have changed ignition wires and no change. And again it runs strong. I have had the carbs rebuilt at Lockwood, but that was 3 years ago, but it didnt seem to make any difference. Any thoughts anyone.
I have 790 hours on the engine.
Mark Donahue
| Quote: | | http://www.matronics.com/Navigator?RotaxEngines-List |
01234
Date: 24/06/2007 08:33
24/06/2007 08:33
[quote][b]
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Tue Jun 26, 2007 3:05 am Post subject: 912 starting problems |
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Mark,
To get a better idea of what you are experiencing, and a basis for
diagnosing the hard starting problem, please let us know exactly how
you do your start procedure and whether it is hard staring when the
engine is cold or hot etc. What is the idle speed of the engine when
warm? Without observing and getting hands on we would need to know
countless little details to make an intelligent guess at what is the
cause of the problem.
I was called in to fix the hot starting problem on a Katana with 912F
engine AFTER the Diamond distributer "fixed" the problem with a new
battery. I removed, disassembled, cleaned and inspected both
carburetors. This aircraft had over two thousand hours on it and I did
not see any entry in the logbook that the engine had been overhauled,
nor any entry about carburetor overhaul. It turned out that one of the
carbs had a starting jet that was too lean and the other had one that
was too rich, the o-rings in a couple places were brittle and cracked,
and there was a bad gasket on one of the starting carbs (enricher). We
replaced jets with proper ones and replaced o-rings and gaskets. Put it
all back together, did a mechanical and pneumatic synch with proper
idle speed adjustment and problem solved.
My point in telling this story is that your problem could be a simple
single thing like incorrect starting procedure or idle speed
adjustment, or it could be multiple problems that will need attention.
Where are you located?
Thom in Buffalo
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Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
- Anonymous |
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Tue Jun 26, 2007 4:15 am Post subject: 912 starting problems |
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I'm not too sure about the carburettor on the 912. If it is one of the
side draft Bing type carbs with the moving main jet than the choke is a bit
of a misnomer on that setup. What is commonly referred to is in fact an
enrichener which allows extra fuel to enter the throat of the carb at low
rpm.
You may find adding a primer, that gives a squirt of gas down the throat of
the carb before starting, may make starting a lot easier for you.
Noel
| Quote: | Time: 10:25:09 PM PST US
From: "markdonahue" <markdonahue(at)earthlink.net>
Subject: 912 starting problems
Kitfox model IV with a 912 UL
Does anyone have some thoughts for me as to how to make my
engine start more
easily.
Engine runs fine after starting. Battery is good and turns
over briskly.
Choke pulls to the stop. Throttle on idle. Have checked
carbs and jets all
are clean and all seems clear. If I add a bit of gas at the
filter it will
fire. Seems like its carb related. Spark seems weak, but
have changed
ignition wires and no change. And again it runs strong. I
have had the
carbs rebuilt at Lockwood, but that was 3 years ago, but it
didnt seem to
make any difference. Any thoughts anyone.
I have 790 hours on the engine.
Mark Donahue
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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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ElleryWeld(at)aol.com
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| Posted: Wed Jun 27, 2007 3:51 am Post subject: 912 starting problems |
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I have been adding a Primer pump to help get the 912's started faster with success
Ellery in Maine
do not archive
**************************************
See what's free at http://www.aol.com. [quote][b]
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Wed Jun 27, 2007 6:27 am Post subject: Re: 912 starting problems |
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Hi Mark,
There are a few things here.
One Thom has touched on. The carbs being rebuilt, but I see you have addressed this even though it was a while ago. How many hours do you have on the rebuilt carbs? Having not synced the carbs could add to your troubles.
If your engine is that old does it have the newer high torque, high speed starter? They come with that starter as of a couple of years ago. My Kolb had an older starter and it was hard to start. The engine has to turn at least 220 rpm (90rpm prop) to start. If it doesn't reach these values then you don't have the spark/energy to start. I switched to the new starter and my battery was marginal in amps so it put a better battery in and it started right away, no hesitation. It was like a different engine. The battery is supposed to be an 18 amp. I know they will start on a smaller battery, but it doesn't really have any reserve power and it's not what Rotax recommends.
Technically, if you have the choke lever engaged, Rotax says it's better to not add any throttle. I have found that when I use the choke and just barely crack the throttle then both of my 912's have started better. I'm sure each engine is different. During the summer I only use about 1/2 choke for my first start of the day.
Just try a few different ways, but check the starter and battery issue, too.
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_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056 |
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jetboy
Joined: 22 Jul 2006
Posts: 233
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| Posted: Fri Jul 20, 2007 3:19 pm Post subject: Re: 912 starting problems |
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A friend has an Avid with the 80 hp 912 and that has suffered 4 causes and cures for the starting troubles.
1/ one or other carbs fall off during start. Cured by attaching carbs to bracket also replacing soft engine mounts. there are 4 SB relating to mounting the carbs.
2/ would misfire and stop when cranking. Cured by changing ignition switches to toggle type so that both carb float bowls could be primed by cranking engine a few seconds before attempting to start.
3/ would fire during cranking but not pick up revs. Started and ran perfectly when propellor removed! Preload was at lower limit. Cured by overhaul and change of the 15 deg dog clutch with the newer 30 deg one in gearbox.
4/ would throw out starter engagement during cranking. Cured by overhaul of sprag clutch on starter motor. there uis a SB for the 912S for this problem. We diagnosed it on the 912UL by carrying out the tests as for the 912S, and the starter current was 10 amps lower than that limit.
You probably dont have the first problem, but any combination of the others could occur. total time is less than 160 hrs.
Ralph
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