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07-17-2019, 07:55 AM
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Join Date: May 2007
Location: Northern CA
Posts: 430
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Rotax Compression Check
Don?t own a Rotax but curious.
Noticed a post calling out compressions of 82/85 etc. on a 100 hp Rotax. Question is are Rotax compression checks done at 85 psi? Most other aviation engines are 80 psi. Is there a specific reason for the he 85 psi?
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07-17-2019, 08:35 AM
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Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,246
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The Rotax maintenance manual calls out 6 bar or 87 PSI. Since the gauge is easier to set for 85, that's what I use. At 450 hours, we have yet to see a detectable drop in pressure... all four are 85/85.
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Dale
Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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07-18-2019, 01:33 PM
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Join Date: Aug 2017
Location: NC
Posts: 31
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You need to read the Rotax manual before attempting. Also, you need the specific compression tester for Rotax. Not one for antique engines. The orifice size is different. A Rotax 9xx should loose little compression through out its life, if cared for correctly.
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07-18-2019, 02:03 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,027
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Quote:
Originally Posted by N456TS
You need to read the Rotax manual before attempting. Also, you need the specific compression tester for Rotax. Not one for antique engines. The orifice size is different. A Rotax 9xx should loose little compression through out its life, if cared for correctly.
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The orifice specified for the tester for a Rotax 912 is .040. That is the same diameter that is used for a Lycoming.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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07-18-2019, 02:17 PM
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Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,246
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Quote:
Originally Posted by rvbuilder2002
The orifice specified for the tester for a Rotax 912 is .040. That is the same diameter that is used for a Lycoming.
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Correct. The aviation specific testers I looked at needed only the correct spark plug adapter.
And in case you're in the mood to save a little money... I looked at numerous similar compression testes intended for automotive use. All look and work the same, but the automotive testers are a fraction of the cost of course. Unfortunately not a single one of them has any detail about the orifice. When I asked, without exception they either simply didn't know or were unwilling to say what it was. I bought one from an aviation supplier.
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Dale
Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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07-18-2019, 02:46 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,027
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Quote:
Originally Posted by DaleB
The aviation specific testers I looked at needed only the correct spark plug adapter.
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We made our own by breaking apart a used spark plug and welding an air fitting onto it.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.
Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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07-18-2019, 03:19 PM
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Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,246
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Quote:
Originally Posted by rvbuilder2002
We made our own by breaking apart a used spark plug and welding an air fitting onto it.
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So did a friend of mine, My welding skills are insufficient.
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Dale
Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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07-19-2019, 02:19 AM
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Join Date: Sep 2018
Location: LSZF
Posts: 418
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no welding equipment here, but bought the 14mm adapter from ACS (12-01283), available from other vendors as well 
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Life's short... Enjoy
DC aka Dan
http://www.aerofun.ch
RV-6.9 #25685, slider, O-360-A3A (carb/dual Lightspeed II), MTV-12-B, HB-YLL owner & lover
RV-4 #2062 HB-YVZ airframe builder
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