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  #11  
Old 05-22-2022, 10:41 AM
Piper J3's Avatar
Piper J3 Piper J3 is online now
 
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Quote:
Originally Posted by Tony_T View Post
Started my annual today. After reading Jim's posts, the muffler was high on my list. Found a pretty nasty crack, almost 180 degrees around the exhaust tube the exits the muffler and also extends into the muffler body just like Jim's. An experienced welder here thinks it will be an easy fix. If that doesn't work out, I guess I will be looking at the new EX-00044 exhaust system. Airplane has 690 hours, my prop has been dynamically balanced from early on.
Tony - When welding a repair on muffler, the inside has to be purged with Argon gas. All muffler openings need to be capped off to contain the Argon. Also, very difficult to clean crack with carbon contamination. The guy that TIG welded my engine mount won't work on mufflers...
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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 780

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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  #12  
Old 05-22-2022, 03:30 PM
Bob Y Bob Y is offline
 
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Not sure of the significance, but it appears the original exhaust springs, # 938 795, have been superseded by part # 938 796. Rotax says the old ones can still be used, but wonder what was changed? Not sure if this might help some of you experiencing issues.
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  #13  
Old 05-22-2022, 08:30 PM
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RicoB RicoB is offline
 
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Could you weld the crack with a regular mig welder instead of tig?
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  #14  
Old 05-22-2022, 10:11 PM
RFSchaller RFSchaller is offline
 
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Talk to a welder about a weld overlay with filler as opposed to just trying to fuse the crack. That way you’ll add some structure and avoid the issue of contaminants in the crack weakening the weld.
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  #15  
Old 05-27-2022, 08:15 AM
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Tony_T Tony_T is offline
 
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Quote:
Originally Posted by Piper J3 View Post
Tony - When welding a repair on muffler, the inside has to be purged with Argon gas. All muffler openings need to be capped off to contain the Argon. Also, very difficult to clean crack with carbon contamination. The guy that TIG welded my engine mount won't work on mufflers...
Jim, our welder ran a TIG bead around the exhaust exit pipe. I'm not a weld expert but it doesn't look completely fused to me. I may end up putting on the new exhaust system. Other's have reported lower cockpit CO with the new system compared to old and the additional clearance to oil cooler is a plus.
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  #16  
Old 05-27-2022, 01:28 PM
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Piper J3 Piper J3 is online now
 
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Tony -

Weld is not the prettiest I've ever seen, but if welder things he had good penetration, I'd say give it try. Might be stronger than when new. I'd inspect fairly often until you have good level of confidence...

Jim
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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 780

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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  #17  
Old 05-30-2022, 02:26 PM
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I put the new exhaust system on mine and have zero co in the cockpit ad my oil temps are much lower. If you want my old exhaust you can have it for the shipping.
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  #18  
Old 05-30-2022, 08:25 PM
seagull seagull is offline
 
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Quote:
Originally Posted by printbr View Post
I put the new exhaust system on mine and have zero co in the cockpit ad my oil temps are much lower. If you want my old exhaust you can have it for the shipping.
What is making the new muffler give you cooler oil temp. Does it sit farther from the oil cooler? What is the distance difference between the two?
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  #19  
Old 05-31-2022, 01:09 PM
Bob Y Bob Y is offline
 
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As a follow up to my post #12, if anyone is interested in the difference between the new 938 796 and old 938 795 exhaust springs, this was the response I received from Dean Vogel at Lockwood:

“If you look at the attached file… the one on the right is the 938 796. Rotax is attempting to get away from the environmental impacts of doing coatings, so they went with one that is stainless steel. The regular steel tends to take the vibration issues better, but it also has a tendency to corrode more quickly.”
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  #20  
Old 05-31-2022, 03:18 PM
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rcarsey rcarsey is offline
 
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I'm unsure which springs my engine came with.. but I can say after about 250 hours, almost all of them have broken by now. I've been replacing with with silver-colored stainless steel springs from Aircraft Spruce, and have not had one break yet.

The old springs seem to corrode quickly with rust and pitting and I've seen them break mid-spring, or just before the hooks at the ends. Luckily safety wire has caught all but one of the breaks.
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