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  #21  
Old 06-28-2012, 07:26 PM
BigJohn BigJohn is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
There are only two maint. interval differences, caused by the (majority of the time) use of 100LL that I am aware of.

1. Plug replacement is supposed to be done every 100 hrs instead of every 200.

2. The first gear box internal inspection is due at 600 hours instead of 800 hours (This is from memory, someone correct me if I have it wrong).
3. Change oil every 25 hours instead of 50.
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  #22  
Old 06-28-2012, 08:10 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by BigJohn View Post
3. Change oil every 25 hours instead of 50.
It figures that someone would catch me on the obvious one.

But it is actually 50 hrs instead of 100, with the most recent revision of the approved fluids service bulletin recommending that with heavy or exclusive use of 100LL, that you do it every 25 hrs (but this is not listed as a requirement in the service schedule).
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  #23  
Old 06-29-2012, 05:40 AM
dick seiders dick seiders is offline
 
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The other obvious unmentioned item is an $8.00 per flying hour additional cost for fuel.
Dick Seiders
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  #24  
Old 06-29-2012, 06:44 AM
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RDOG RDOG is offline
 
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Quote:
Originally Posted by dick seiders View Post
The other obvious unmentioned item is an $8.00 per flying hour additional cost for fuel.
Dick Seiders
Wow, that becomes a big number. $8.00 an hour times 600 hours = $4,800 in additional cost by using 100LL.
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  #25  
Old 06-29-2012, 08:49 AM
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Geico266 Geico266 is offline
 
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Quote:
Originally Posted by MLock View Post
As an additional note, next week New Blue is going down for annual. We'll be changing oil, plugs, wiping out the oil tank, rebuilding the carbs, changing coolant, and everything our Rotax mechanic out here says we need to do.

Believe me, if I see something that can attributed to the steady diet of 100LL it gets, I'll be certain to let everyone know.
Mitch, it is the $3000 sprague clutch (shop replacement cost) that is very susceptable to loading up with lead. Talk to the guys that overhaul them, don't take my word for it. I had to replace one in a 912 10 years ago or so. A major PITA, and expensive.


When you clean out the oil tank you will find lead has settled in the bottom like mud. This is the same lead that collects and coats the sprage clutch and loads up the springs and "bearings" that grab the crank when starting. If it starts slipping (or the engine kicks back) it can ruin the sprage clutch.

The lead also collects in the piston rings as the tolerances are extremely tight. Some rings have been stuck due to lead fouling.

My experience comes from the school of hard knocks and costly replacement. Your milage may vary.
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Last edited by Geico266 : 06-29-2012 at 08:58 AM.
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  #26  
Old 06-29-2012, 10:11 AM
MLock MLock is offline
 
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I don't doubt you one little bit , Larry. Known you too long for that. I'm just sharing my experience as you have yours. Hopefully I'll be spared the troubles you had. But no matter what I go through, I'm going to share it here.
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  #27  
Old 06-29-2012, 11:54 AM
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One difference in Mitch's operating with 100LL exclusively, that may get a different result from past experiences, is that he has been using Decalin from the very beginning. It goes a long way in savaging the lead out of the inside of the engine and it's related systems. I look fwd to hearing what amount of lead he finds in the bottom of the oil tank. <Mitch, will you try and get a good quality photo?>

BTW, Mitch's Blue RV-12 and the red demonstrator (N412RV) have been purposely being operated completely opposite, as far as fuel usage goes, to gain some first hand experience.

Mitch's engine has operated exclusively on 100LL (except the first 200 hrs which was about 50/50 between auto fuel and 100LL)

N412RV has been operated 600+ hrs, exclusively on auto fuel, except for the occasional long cross country (maybe 20 hrs per year, average)
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  #28  
Old 06-29-2012, 12:17 PM
MLock MLock is offline
 
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I'll try to get as good a picture as I can, but I'm not expecting to find much as we wipe the cannister everytime we change the oil. Our Rotax guy out here, Ed Johnson, does most of the engine maintenance and has never expressed a concern about a large amount of lead in the tank.

And for you John (and everyone), Ed will be doing the rebuild on the carbs so we won't be sending them out. I bought a two carb rebuild kit from Leading Edge Airfoils for $147.00 which consisted of gaskets and some small screws.
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  #29  
Old 06-29-2012, 02:55 PM
fly3g fly3g is offline
 
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[quote=Geico266;674472]Mitch, it is the $3000 sprague clutch (shop replacement cost) that is very susceptable to loading up with lead. Talk to the guys that overhaul them, don't take my word for it. I had to replace one in a 912 10 years ago or so. A major PITA, and expensive.

Larry interesting about the spague clutch, my hangar mate has a 912S in a Kitfox and he had his sprague clutch replaced at around 450hrs and then it failed big time at 800 hours (on downwind the engine bucked, apparantly locked up the starter, spun it up till it melted and then disintegrated the sprague into the running engine internals), to the 912's credit it kept running till shutdown, figured out there was a real problem when it wouldn't re-start. Bottom line engine worth only core value and had to buy a new one. Although in his case the engines diet was probably 80%mogas/20%leaded with 25 hr oil changes. I didn't realize other folks were seeing sprague problems, the Rotax guys didn't allude to any of that when he talked to them. Wonder if it's a weak spot in the design?
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  #30  
Old 06-29-2012, 03:15 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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[quote=fly3g;674595]
Quote:
Originally Posted by Geico266 View Post
Mitch, it is the $3000 sprague clutch (shop replacement cost) that is very susceptable to loading up with lead. Talk to the guys that overhaul them, don't take my word for it. I had to replace one in a 912 10 years ago or so. A major PITA, and expensive.

Larry interesting about the spague clutch, my hangar mate has a 912S in a Kitfox and he had his sprague clutch replaced at around 450hrs and then it failed big time at 800 hours (on downwind the engine bucked, apparantly locked up the starter, spun it up till it melted and then disintegrated the sprague into the running engine internals), to the 912's credit it kept running till shutdown, figured out there was a real problem when it wouldn't re-start. Bottom line engine worth only core value and had to buy a new one. Although in his case the engines diet was probably 80%mogas/20%leaded with 25 hr oil changes. I didn't realize other folks were seeing sprague problems, the Rotax guys didn't allude to any of that when he talked to them. Wonder if it's a weak spot in the design?
I think you are talking about a different sprague clutch . There is one in the main PSRU gear box and there is a small one just for the starter motor.
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