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  #1  
Old 11-13-2015, 08:14 PM
R100RS R100RS is offline
 
Join Date: Jan 2014
Location: USA
Posts: 31
Default RV-12 912 ULS carb jetting

I have looked but with no success. If I recall correctly, the RV-12 uses individual oiled fabric air filters on the carbs (rather than a single air box).

Can someone provide the RV-12 factory jetting for the Bing Carbs? My best guesses are:

Main jet: 155 or 158?
Needle jet: 2.70?
Idle jet: 35?
Needle clip position?

Thanks!

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  #2  
Old 11-14-2015, 05:09 AM
aerofurb aerofurb is offline
 
Join Date: Jul 2009
Location: High Wycombe, UK
Posts: 288
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Your best bet would be to check the Rotax manuals. The carbs are not airframe specific.

In my experience, the uncertified 912ULS in the RV-12 normally uses individual K&N air filters and the certified 912S tends to have the single airbox fitted.
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  #3  
Old 11-14-2015, 06:11 AM
R100RS R100RS is offline
 
Join Date: Jan 2014
Location: USA
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Jerry, yes, I have consulted the manual. However, because air box configuration and air filtration systems have effects on jetting, I was asking specifically for the jetting of the engine equipped with two individual filters.

Do you have that information?
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  #4  
Old 11-16-2015, 03:08 PM
aerofurb aerofurb is offline
 
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Location: High Wycombe, UK
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Nope. I don't have that info, I'm afraid.

As Rotax supply both the air box and the K&N filters for their engines, I have always presumed Rotax have our (and their) best interests at heart and have set the carbs correctly out of the box.
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  #5  
Old 11-16-2015, 10:00 PM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
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Have you tried contacting the ROTAX Owner Assistance Network?
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  #6  
Old 11-17-2015, 06:09 AM
Sink Sink is offline
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Join Date: Apr 2015
Location: Altha, FL.
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The carb jetting from factory doesn't change if you use 2 individual air filters or one single large one. Some do change the jetting if they live at high elevations and fly high altitudes all the time. If you do have 2 single air filters and they only use under the cowl air then it is like running with a moderate carb heat all the time. The best air for the engine would be cool dry outside air. Under the cowl uses the warm to hot air under a cowl. This makes the carbs run just a touch rich.

Here is a carb jet chart.
http://www.rotaxservice.com/rotax_ti...arburetors.htm

Unless you live at high elevations I would leave the jetting as is.
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  #7  
Old 11-17-2015, 11:23 PM
R100RS R100RS is offline
 
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Location: USA
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Sink, thanks for the chart. I have seen those numbers before.

700 ft elevation. Yes, warm air is less dense than cool air and yes, at least hypothetically, warm air from inside the cowling should result in a (small) loss of HP. Still, many 912-equipped planes use individual oiled cotton filters rather than outside air and many of them have excellent performance. I have yet to see any quantification of power loss from warmer air drawn into the carbs from the cowling.

I guess nobody changes 912 ULS jetting when air filter configuration is changed.
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