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  #1  
Old 10-18-2017, 06:27 PM
Art_N412SB Art_N412SB is offline
 
Join Date: Sep 2017
Location: Gig Harbor
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Question Rotax 912ULS Idle speed to high

Hello friends,
I am new to the RVs and the Rotax engines. As a matter of face after 50 years of professional aviation this is my first aircraft ownership. I picked a great airplane to buy into. 3 of us own this RV12. I have had 4 flights in it and am in love.
So this week finds us doing a 100/200 hour inspection at 400 hours of airframe time. The engine ran flawlessly going into the inspection. But when we rolled it out to do the carb sync, suddenly the idle rpm went to 2500. We are having a tough time figuring out what the difference a day would make.
Let us suppose that we went through all of the obvious things. (which are not obvious to me) and we decided to do an idle speed adjustment. The Rotax maintenance manual 10.5 Idle speed adjustment procedure refers in step 1 to adjusting the idle mixture screw. Is that a factory only adjustment? Do you guys ever adjust the engine idle speed using this screw in addition to the idle speed adjustment screw of the throttle valve?
Thanks a bunch,
Art
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  #2  
Old 10-18-2017, 06:38 PM
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Jetguy Jetguy is offline
 
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Location: Texas, Fort Worth
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The engine ran flawlessly going into the inspection. But when we rolled it out to do the carb sync, suddenly the idle rpm went to 2500.

Did you mess with the carbs in any way during the inspection?
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  #3  
Old 10-18-2017, 07:05 PM
Ernie Ernie is offline
 
Join Date: Feb 2011
Location: Richland, Wa
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Any adjustment to the throttle cable threads will likely require readjusting the idle stops. Recommend you watch the Carburator Syc video at info@rotaxowner.com
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  #4  
Old 10-18-2017, 09:10 PM
RFSchaller RFSchaller is offline
 
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Location: Phoenix, AZ
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You can adjust the idle mixture screw, but at the ROTAX course the guy told us most people who mess with it cause more issues. The ROTAX manual tells you to set it by screwing it in and then backing off a set number of turns I think 1 1/2: but I don’t remember for sure. It should have been set at the factory, and unless you changed it I wouldn’t mess with it.
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  #5  
Old 10-18-2017, 09:32 PM
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Phantom30 Phantom30 is offline
 
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Location: Coeur d'Alene, ID/Casa Grande, AZ
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Quote:
Originally Posted by RFSchaller View Post
You can adjust the idle mixture screw, but at the ROTAX course the guy told us most people who mess with it cause more issues. The ROTAX manual tells you to set it by screwing it in and then backing off a set number of turns I think 1 1/2: but I don’t remember for sure. It should have been set at the factory, and unless you changed it I wouldn’t mess with it.
1 1/2 turns is correct...
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  #6  
Old 10-18-2017, 09:45 PM
Driftdown Driftdown is offline
 
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Location: Clearwater, Florida
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Quote:
Originally Posted by Ernie View Post
Any adjustment to the throttle cable threads will likely require readjusting the idle stops. Recommend you watch the Carburator Syc video at info@rotaxowner.com
Excellent suggestion.
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  #7  
Old 10-18-2017, 10:50 PM
Azjulian Azjulian is offline
 
Join Date: Dec 2015
Location: Scottsdale, Arizona
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check the idle stops (the brass stops that you lock in position with the tiny allen key) its easy to have those setup to prevent you getting to a low enough throttle cable position.
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  #8  
Old 10-19-2017, 12:20 AM
Art_N412SB Art_N412SB is offline
 
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Location: Gig Harbor
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The only thing we did was to remove, clean, and replace the filters.
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  #9  
Old 10-19-2017, 12:22 AM
Art_N412SB Art_N412SB is offline
 
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Thanks, I will watch the video. I looked at one on Youtube of a complete overhaul of the carburetor. That was pretty interesting. Took about an hour though.
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  #10  
Old 10-19-2017, 12:23 AM
Art_N412SB Art_N412SB is offline
 
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We adjusted the idle stops to book specks, with no luck.
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