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Catz631(at)aol.com
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 Posted: Sat Feb 02, 2008 5:50 am Post subject: 912 carb overhaul |
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Last week I finished the Lockwood Rotax school. We completely went through the carb(each of us had a carb to disassemble and rebuild) and it was a very good course. One of the things they mentioned was to NEVER take the screws out of the butterfly valve. The chances of messing it up are great! They said to send it in for overhaul if for some reason you need to do that. I just replaced the diaphragm and float needle in my 912 yesterday at 150 hours and like Jack, the parts I replaced were in great shape (even though it had been at least 10 years since they were done and replacement should be done every 5 years) except for the float bracket which had a dimple in it and will have to be replaced.
I purchased my Kitfox 2 months ago and am going through the engine to update it as it is an early engine. (carbs,hoses,etc.) I only mention the butterfly because the instructor emphasized not to do it. I know most of you guys know more about these engines then I do.My background is Lyc/Cont. I went to school to learn about the Rotax 912
Dick Maddux
Kitfox 4-1200
Pensacola, Fl
Who's never won? Biggest Grammy Award surprises of all time on AOL Music.
[quote][b]
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jack.kuehn(at)gmail.com
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| Posted: Sat Feb 02, 2008 8:14 am Post subject: 912 carb overhaul |
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The only reason to remove the throttle butterfly is to replace the
O-ring on the shaft. This is one O-ring that would likely see some
wear, it would seem to me, because it moves each time you use the
throttle! If it wears out and leaks, you have a manifold leak. WHat
is the problem with taking out the screws? WHat did they say is going
to get messed up? If you pean over the threads on the new screws, how
can there be a problem? And it is not that difficult to assemble the
shaft/butterfly so that it operates as good as new.
Jack
On Feb 2, 2008 6:47 AM, <Catz631(at)aol.com> wrote:
| Quote: |
Last week I finished the Lockwood Rotax school. We completely went through
the carb(each of us had a carb to disassemble and rebuild) and it was a very
good course. One of the things they mentioned was to NEVER take the screws
out of the butterfly valve. The chances of messing it up are great! They
said to send it in for overhaul if for some reason you need to do that. I
just replaced the diaphragm and float needle in my 912 yesterday at 150
hours and like Jack, the parts I replaced were in great shape (even though
it had been at least 10 years since they were done and replacement should be
done every 5 years) except for the float bracket which had a dimple in it
and will have to be replaced.
I purchased my Kitfox 2 months ago and am going through the engine to
update it as it is an early engine. (carbs,hoses,etc.) I only mention the
butterfly because the instructor emphasized not to do it. I know most of you
guys know more about these engines then I do.My background is Lyc/Cont. I
went to school to learn about the Rotax 912
Dick Maddux
Kitfox 4-1200
Pensacola, Fl
________________________________
Who's never won? Biggest Grammy Award surprises of all time on AOL Music.
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--
Jack Kuehn
5565 Brady Ln
Lolo, MT USA 59847
(406)273-6801
(406)546-1086 cell
jack.kuehn(at)gmail.com
(406)273-2563 fax
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Gilles.Thesee(at)ac-greno
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| Posted: Sat Feb 02, 2008 8:35 am Post subject: 912 carb overhaul |
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Jack Kuehn a écrit :
| Quote: |
The only reason to remove the throttle butterfly is to replace the
O-ring on the shaft. This is one O-ring that would likely see some
wear, it would seem to me, because it moves each time you use the
throttle!
|
Agreed, but according to our Rotax dealers, the throttle is best left
alone as long as there is no problem. Which they say is rare.
After all, in a 2 hour cross country flight, the Rotax throttles won't
move much : some movement at engine checks, then travel from idle to
full throttle, then back to cruise setting until approaching destination
Adding those angular movements will not amount to more than the
equivalent of a few turns, which O-ring can easily endure many many times.
| Quote: | If it wears out and leaks, you have a manifold leak. WHat
is the problem with taking out the screws? WHat did they say is going
to get messed up?
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One should be careful to file away the peened screw ends lest the
threads in the throttle shaft get damaged when removing the screw.
Best regards,
--
Gilles
http://contrails.free.fr
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ricklach
Joined: 20 Jun 2006
Posts: 127
Location: Kernville, Calif.
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| Posted: Wed Feb 20, 2008 10:17 am Post subject: Re: 912 carb overhaul |
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There are two serious issues when removing the butterfly.
1. During reinstallation the alignment of the butterfly to the carb throat must be perfect. Other wise it will not idle properly. If you get them both off, it will never run right.
2. The screws that come out should be replaced with new ones. Getting a safe crimp the second time is iffy. If the crimp is not done right the screw could come out and into the motor it goes.
Hope this helps.
Rick
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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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| Posted: Wed Feb 20, 2008 3:44 pm Post subject: Re: 912 carb overhaul |
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Hi All,
The Type 64 carb is a great carb and they tend to last hundred of hours with out any issues. I did pull two older carbs apart last week and found torn "O" rings. They will dry out and tear. The 200 hour inspection is just that. Everything should be pulled apart and the "O" rings replaced with a very light coating of litium grease, do not glob it on. Wipe off any excess. The smaller rebuild kit comes with everything you need. Make sure the enrichner screws (4 on each carb) get blue loctite. The butterfly is really not a big deal and here is how to do it. By the way the 2 little butterfly screws come in the rebuild kit.
First detach the throttle spring. Open the butterfly valve so it is flat in the throat. These two little screws have been slightly peened over on a thread so they can not come unscrewed and drop into the engine. Use a small file or a dremel tool and lightly file down the screws on the threaded side. Once down they will unscrew. Use a good straight tipped screwdriver in the slot. Don't use a beat up or rounded head flat blade screwdriver. Use one with a good tip. The screws will come right out. If they are too tight and I have only seen one like this then use a heat gun on it and warm it up. The butterfly has a demple on it. The demple always goes up and faces out. Take out the butterfly and replace the "O" ring on the shaft and use a very light coat of lithium grease. Replace the butterfly and then the 2 screws. The butterfly will align itself with the screws and because the butterfly has to line up to fit in the throat of the carb. No loctite on the screws. The 2 screws now need to be peened over slightly. The easiest way is to put a 1 3/8" solid bar stock of steel or aluminum in a vise. Make it about 6" long. Take the carb and close the butterfly and set the end of the carb down over the metal bar. The head of the screws will now be against the metal and the butterfly bar will be supported. Now look down through the carb and you will see the screw ends and threads. Take a small hammer and a small flat punch and peen the tops of the 2 screws. Don't go crazy just tap the threads to keep the screw from working its way out if it were to loosen. You are now done.
Just got through showing people in a class. I don't think they think it's a big deal anymore. It is fairly easy.
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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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