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  #1  
Old 08-04-2021, 12:06 PM
todehnal todehnal is offline
 
Join Date: Jan 2005
Location: Kentucky Lakes area in KY
Posts: 974
Default Found the Cause and now Need the Fix

I've been fighting vibration, short spark plug life and very dirty oil.
I got a tip from the Rotax booth at Oshkosh and he convinced me that I had an intake leak. So, when I got home, I built a simple smoke machine. I hooked it it and it quickly became obvious that I do, indeed have an itake leak. Both carb rubber sockets have leaks coming from between the rear surface of the drip pans, and the carb sockets.

Before leaving Oshkosh, I stopped by Lockwood and picked up 2 new carb sockets, and the parts lady she asked if I was using drip pans. When I told her that I was, she said that I also needed 2 new "O" rings and 2 gaskets, which she provided for me.

After getting home, I refered to my buildng plans and found no mention of adding a gasket. I then went to the parts manual to determine the exact orientation of the "O" rings and gaskets. The figure: 73-10-00-1 shows the gasket replacing the "O" ring and relocating the "O" ring to the surface between the socket and the drip pan. NO WAY WILL THIS WORK ! The layout of the figure must be decieving.

If anyone knows and could share the exact orientation of these parts, it would be greatly appreciated. This may also help someone else who is doing the 5 year rubber socket replacement. Thanks..........Tom
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2013- RV12, Kit #119. N123M First flight Nov21. It's a keeper!
1998- RV-9 tail kit, built and sold
1989- RV-6 tail kit, built and sold
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  #2  
Old 08-04-2021, 01:26 PM
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rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,599
Default

I would suggest using extreme care in reassembling as illustrated in the parts manual (IPC)
I know of at least one engine that was destroyed because of a bad induction leak when the o-rings were installed on the same side of the drip tray as the carb socket.

The RV-12 ULS KAI specifically shows the o-ring on the manifold side of the drip tray, and nothing additional added on the carb. socket side.
The standard carb. socket has an integral o-ring molded into it which takes care of sealing on that side (unless you introduce a second o-ring that cant be kept in the proper position).

EDIT - I just looked through our archive of superseded Rotax documentation and found that in the 2010 version, it also showed a gasket but it was co-located with the o-ring on the manifold side of the drip tray.

Additional edit - I have an e-mail out to our USA Rotax tech. support contact. I will post here what I find out.
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Scott McDaniels
Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop Manager
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RV-6A (aka "Junkyard Special ")

Last edited by rvbuilder2002 : 08-04-2021 at 01:49 PM.
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  #3  
Old 08-04-2021, 02:09 PM
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Piper J3 Piper J3 is offline
 
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Location: Hinckley, Ohio
Posts: 2,543
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O-ring on the manifold side of the drip tray, and nothing additional added on the carb. socket side. The standard carb. socket has an integral O-ring molded into it which takes care of sealing on that side.

My RV-12 Rotax 912ULS is assembled as described above.

Assembly is done dry, but if you like, you good use some O-ring grease sparingly...
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 735

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father - CFI) - USAAF 1st Lt. Captain B-17H
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  #4  
Old 08-04-2021, 02:17 PM
todehnal todehnal is offline
 
Join Date: Jan 2005
Location: Kentucky Lakes area in KY
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Scott, thanks so much for persuing the best fix for this leak. The smoke test clearly showed the leak to be between the drip tray, and the carb socket. I would have thought that the integral ring molded into the rubber sockets would have sealed these mating surfaces, but both of mine are leaking. Mearly adding the gasket to the front of the drip tray surface will not be beneficial to my situation. I think that I would need to replace the original "O" rings, add the gaskets between the drip tray and the replacement rubber socket that I bought. However, I will not move forward until I hear back from your inqueeries. Thanks..........Tom
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2013- RV12, Kit #119. N123M First flight Nov21. It's a keeper!
1998- RV-9 tail kit, built and sold
1989- RV-6 tail kit, built and sold
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  #5  
Old 08-04-2021, 02:33 PM
seagull seagull is offline
 
Join Date: Dec 2019
Location: San Bernardino
Posts: 394
Default

Quote:
Originally Posted by todehnal View Post
I've been fighting vibration, short spark plug life and very dirty oil.
I got a tip from the Rotax booth at Oshkosh and he convinced me that I had an intake leak. So, when I got home, I built a simple smoke machine. I hooked it it and it quickly became obvious that I do, indeed have an itake leak. Both carb rubber sockets have leaks coming from between the rear surface of the drip pans, and the carb sockets.
Great post! I’m interested in the outcome.

Would you mind explaining how you built the “simple smoke machine” and how you hooked it up?
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  #6  
Old 08-04-2021, 03:22 PM
todehnal todehnal is offline
 
Join Date: Jan 2005
Location: Kentucky Lakes area in KY
Posts: 974
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Quote:
Originally Posted by seagull View Post
Great post! I’m interested in the outcome.

Would you mind explaining how you built the “simple smoke machine” and how you hooked it up?
No problem Walt, That is if you can keep from laughing at this.
I started with a half gallon jar with a wide mouth metal lid. I drilled 2 holes just under the size of tubless tire rubber valve stems (valve stems removed) and popped them in from the bottom with a pair of pliers. I had an cheap old straight electric soldering iron, cut off the cord and installed it through another hole that I drilled into the lid and re-attached the cord with wire nuts. The idea was to keep the holes in the lid sealed as well as possible. You could use a high temp silicone sealer if you wanted

Now to use it: You will need a bicycle tire pump, a couple of rubber gloves, a 3 or 4 foot length of plastic tubing about 1/4" size, a couple of old shop towels and some mineral oil or baby oil will work just as well.
I popped out both carbs and replaced them with the rubber gloves to seal the intake ports. I cut off one finger tip and inserted one end of the plastic tubing into it and clamped it with a hose clamp. The other end was pushed tightly over one of the valve stems. I attached the tire pump to the other rubber valve stem. Wrap a few old shop towels around the tip of the soldering iron and soak them very well with the mineral oil. The soldering iron and old soaked rags go ito the jar and close the lid tightly. Now plug in the soldering iron and wait about 5 minutes while the jar fills with smoke. Start slowly operating the tire pump and watch the rubber gloves inflate. After a few minutes you will see smoke if you have an intake leak.

Are you laughing yet? It really worked for me and it led me directly to the source of the leaks. Hope this helps. Oh, my shirt still smells like smoke. ......Tom
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2013- RV12, Kit #119. N123M First flight Nov21. It's a keeper!
1998- RV-9 tail kit, built and sold
1989- RV-6 tail kit, built and sold
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  #7  
Old 08-04-2021, 05:43 PM
seagull seagull is offline
 
Join Date: Dec 2019
Location: San Bernardino
Posts: 394
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Not laughing at all, great idea, I like the “MacGyver” approach.
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  #8  
Old 08-04-2021, 05:50 PM
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N804RV N804RV is offline
 
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Location: Mount Vernon, Wa
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Another problem with using the IPC as an assembly guide is that you have to make sure you understand the vendor's method for annotating applicability for different model/year parts.

I know of more than one occasion when someone tried to put a newer part in an older assembly that was no longer applicable.
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  #9  
Old 08-04-2021, 08:10 PM
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Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
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Default

Quote:
Originally Posted by todehnal View Post
Scott, thanks so much for persuing the best fix for this leak. The smoke test clearly showed the leak to be between the drip tray, and the carb socket.
When manifold leakage is fixed please report back on vibration, short spark plug life and very dirty oil. I'll be interested if fix solves any of these problems...
__________________
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 735

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father - CFI) - USAAF 1st Lt. Captain B-17H
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  #10  
Old 08-04-2021, 08:31 PM
olegusan olegusan is offline
 
Join Date: Aug 2014
Location: Melbourne, Australia
Posts: 38
Default

I wonder why the drip tray installed between the rubber socket and the intake?

Wouldn't it be better to attach it on other side of the rubber socket keeping it in place with the same bolts as the socket?

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RV-12 # 120877 VH-TAO (Flying)
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Last edited by olegusan : 08-04-2021 at 08:41 PM. Reason: added image
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