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  #31  
Old 03-16-2017, 09:58 AM
David-aviator David-aviator is offline
 
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Quote:
Originally Posted by LettersFromFlyoverCountry View Post
The one negative about having to go from an IO-360 to the Rotax in the RV-12 I'm building is having to go back to a carbureted engine.
And the springs driving to WOT, I don't like it.
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  #32  
Old 03-16-2017, 10:46 AM
h&jeuropa h&jeuropa is offline
 
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This might apply in this situation. It might also apply when carb ice is suspected.

A few Rotax 912S powered Europa aircraft have suffered similar power loss. The problem eventually was traced to a small exhaust leak at the cylinder head exhaust pipe joint or from a joint in the exhaust system allowing hot exhaust to hit the carb bowl causing the fuel to evaporate. You may see a tan soot line from the exhaust to the carb bowl. This will only happen on 912 engines that are not fitted with carb bowl drip trays. Often the engine will run fine after the throttle is reduced since the exhaust is cooler and the carb bowl has a chance to refill.

The solution is to fit carb bowl drip trays. They are a standard Rotax part or you can fabricate your own. They are also a good idea in general since should the carb bowl overflow for any reason, the gas may drip on to the exhaust pipe!

Jim Butcher
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  #33  
Old 03-16-2017, 10:47 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by rv6ejguy View Post
Oil change intervals are reduced using 100LL and Rotax techs tell me that gearboxes on engines using 100LL are pretty gunked up with lead, even with the shorter oil drain intervals.
I am aware of the specifics related to operating with 100LL (one of our RV-12's has been operated for years using it exclusively).
I guess I disagree on that that translating too to "Bad things will happen".
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  #34  
Old 03-16-2017, 11:32 AM
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Piper J3 Piper J3 is offline
 
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Quote:
Originally Posted by David-aviator View Post
And the springs driving to WOT, I don't like it.
The 912 series engines need to be looked at as if they are two separate power plants coupled to a single crankshaft. This is because each “half” has its own carburetor and induction system unlike traditional aircraft engines where all cylinders share a single carburetor.

Reason for springs on 912 carbs is for safety. If throttle cable fails on one side of the engine you will have partial throttle – perhaps zero to something approaching 100%. Say the other side is still functioning correctly with its half of the throttle cable intact. Worse case scenario would be 0% power on one side and cruise or full power on the other side. Engine would probably shake itself loose from it’s mounting.

The springs are designed to advance power to full if throttle cable breaks. With opposite half of engine already at controlled cruise power the engine continues to run smoothly and makes sufficient power for continued flight. In this case the pilot will need to judge height for safe landing and then kill engine by shutting off ignition to prevent the power imbalance described above.

The springs are there for safety…
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  #35  
Old 03-16-2017, 11:49 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
I am aware of the specifics related to operating with 100LL (one of our RV-12's has been operated for years using it exclusively).
I guess I disagree on that that translating too to "Bad things will happen".
Nothing bad is likely to happen other than you may end up taking apart the gearbox before TBO and at overhaul, more pieces inside that gearbox may have to be replaced. Those are perhaps small prices to pay compared to an engine out caused by vapor lock and winter mogas. The best scenario will be when proper unleaded avgas is widely available.

Then again, some folks could ditch all these problems by replacing carbs with EFI as some others have done on the 912s.
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  #36  
Old 03-16-2017, 11:58 AM
AZLeeJay AZLeeJay is offline
 
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Location: Phoenix
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Most of these comments seem to support the new Swift unleaded avgas. I hope it comes to a FBO near me.
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  #37  
Old 03-16-2017, 01:46 PM
cactusman cactusman is offline
 
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A bad thing to me is taking off at an 8000' Dalt with a family member or friend and seeing nothing but pine trees, forest roads and homes after an engine failure due to vapor lock....putting up $800-1500 for a professional gearbox rebuild a little early is simply the cost of doing business.

Switching to 100LL for the majority of your fueling needs in the hotter climes of the southwest when "watered down" winter gas with ethanol is being pumped is also just the cost of doing business.

My 2 cents.
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  #38  
Old 03-16-2017, 01:54 PM
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Phantom30 Phantom30 is offline
 
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Quote:
Originally Posted by cactuspilot View Post
A bad thing to me is taking off at an 8000' Dalt with a family member or friend and seeing nothing but pine trees, forest roads and homes after an engine failure due to vapor lock....putting up $800-1500 for a professional gearbox rebuild a little early is simply the cost of doing business.

Switching to 100LL for the majority of your fueling needs in the hotter climes of the southwest when "watered down" winter gas with ethanol is being pumped is also just the cost of doing business.

My 2 cents.
Couldn't agree more with you....I'll be mixing 60/40 % (40 % LL) during Winter/Spring months to minimize lead build up. Even in Summer @ high altitude airfields....just for peace of mind. A sputtering engine would freak my wife out!!
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  #39  
Old 03-16-2017, 04:18 PM
rgmwa rgmwa is offline
 
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Quote:
Originally Posted by David-aviator View Post
Robert,

Is the Hodges test kit available in Australia?
David... see PM's.
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  #40  
Old 03-16-2017, 05:41 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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Quote:
Originally Posted by David-aviator View Post
And the springs driving to WOT, I don't like it.
Take a careful look at your M-S carb, or Bendix style injector servo.....
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