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2-stroke muffler weak area

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Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Tue Aug 17, 2010 2:57 pm Post subject: 2-stroke muffler weak area

Several years ago when I still had the 532 on my MKIII, I was on the way home one afternoon when suddenly the exhaust became incredibly louder. My wife heard the noise when I was still a couple miles away. Got home and discovered that one side or half of the curved expansion section had blown loose. It had failed so badly that the only thing still unbroken was the area next to the inlet cone.



Welded it back and mentioned it to a friend, and as it turns out, the same thing had happened to him, it was the 503 on his Drifter.



Today a friend flying a CGS Hawk dropped by and mentioned that his exhaust had been louder for the last couple flights, and he asked me to look at it. His was in the process of splitting, so we hauled out the welding tanks and welded it up while it was sitting out on the air strip. 



After I got done, it occurred to me that maybe this is info that needs to passed along, so here are some pics. Would have been better if I had thought of the camera first, but our priority was getting him home safely.



I guess this is not specifically Kolb related, and this is only the third one I have seen in over ten years, but since a lot of us use this sort of muffler, I thought it worth passing on, maybe it ought to be a preflight item? 



Not the prettiest welding job I ever did, but when you are standing on a stool, on your tip toes leaning over the top of the muffler and sweating like a hog - I don't care. 



You can see where the split was - right up the stamped seam, and then where the expansion section ties into the can, it had split for a couple inches in both directions across the top. Welding that was pretty cobby,  real thin stuff next to a thick section that was factory welded. Not even sure if I got all of it, but where I was standing, I couldn't even see it all. But it got him home safe, and he can always bring it back tomorrow in the trunk of his car if I missed a spot.



Richard Pike

MKIII N420P (420ldPoops)

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williamtsullivan(at)att.n
Guest

Posted: Tue Aug 17, 2010 3:23 pm Post subject: 2-stroke muffler weak area

Richard- What kind of filler rod did you use on this?  I also see a reinforcing strap going from the muffler to the inlet pipe.  Was this a factory option at one time?  Mine is all salt rotted and stress cracked.  I welded some of the cracks with a flux core MIG, but I also have a torch, just no steel filler rod.  Your welding looks pretty good from here.

  

                                                  Bill Sullivan

                                                  Windsor Locks, Ct.

                                                  FS 447

 [quote][b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Tue Aug 17, 2010 3:48 pm Post subject: 2-stroke muffler weak area

Today a friend flying a CGS Hawk dropped by and mentioned that his exhaust 

had been louder for the last couple flights, and he asked me to look at it. 

His was in the process of splitting, so we hauled out the welding tanks and 

welded it up while it was sitting out on the air strip.

Richard Pike

MKIII N420P (420ldPoops)



Richard P/Gang:



My first impression of the Rotax silencer was the amount of material that 

has been lost over the years this system has been in service.  Not a whole 

lot of steel left in that old can.



Disentegration of Rotax mufflers is pretty common, especially if the 

operator puts a lot of hours on them.  The system is operating on exhaust 

pulses.  I believe it is those pulses that are working the can and causing 

the failures.



john h - Who experienced a loub noise from my 447 about 10 miles west of 

Quincy, Florida, more than 20 years ago.  My Rotax muffler was coming apart 

in the neck.

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Tue Aug 17, 2010 3:48 pm Post subject: 2-stroke muffler weak area

Richard- What kind of filler rod did you use on this?

                                                 Bill Sullivan

                                                 Windsor Locks, Ct.

                                                 FS 447



 Bill S/Gang:



Coat hangers work well when there is nothing else available.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

williamtsullivan(at)att.n
Guest

Posted: Tue Aug 17, 2010 4:03 pm Post subject: 2-stroke muffler weak area

Thanks, John.  I have used coat hangers on sheet metal before.  I like gas welding over MIG on the old stuff- less cracking after.  I have also used annealed mechanic's wire.

   My muffler will have to be replaced in a while- too much salt pitting from when it was on Long Island.

  

                                                   Bill Sullivan

                                                   Windsor Locks, Ct.

                                                    FS 447

 [quote][b]

flykolb(at)pa.net
Guest

Posted: Tue Aug 17, 2010 4:09 pm Post subject: 2-stroke muffler weak area

The earlier engines did not have a separate 90 degree elbow - these had a

one piece manifold/elbow - these would break.



Later on came the separate elbow which gave an additional degree of freedom

for the muffler system.



I couldn't quite tell from the photos which type this was.



Dennis



--

Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Tue Aug 17, 2010 5:17 pm Post subject: Re: 2-stroke muffler weak area

Wow! several questions - 



It was mild steel 1/16" welding rod. 



I saw that reinforcing strap also, the current owner is not the builder, so...?



John - roger that on the pulses taking it apart, that is one of the reasons I went to the Quicksliver style exhaust on my current MKIII installation, it just looked less stressed. The curlyque style is also semi-cantilever mounted off the side, so I am thinking that the Quicksilver type down along the engine axis, ought to have less stress. I added a picture of it.



However the one on the Hawk was partly operator error in addition to the exhaust being old, he was doing a mag check a few days ago and inadvertently turned everything off, then promptly turned it back on, it made a loud backfire, and immediately the exhaust was notably louder.

(Dude! You blew it up!)



Dennis, I looked at the other pics I took, it doesn't show in any of them but I am pretty sure it is the 3 part setup, I remember seeing six springs total so it would have to have had the separate elbow.



Richard Pike

MKIII N420P (420ldPoops)

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ropermike

Joined: 28 Aug 2006
Posts: 40
Location: West Texas, South Mississippi

Posted: Fri Aug 20, 2010 5:11 am Post subject: Re: 2-stroke muffler weak area

I have welded cracks in mine several times. I had to drill small hole at both ends of the crack and weld it with a torch and bailing wire. A friend of mine had a muffler shop and he used bailing wire all the time. The challenge is finding a piece of bailing wire that is not rusted. Of coarse the crack has to be buffed clean and I let it cool slowly after welding.

_________________
The next best thing to playing and winning is playing and losing!...Mike Hillger

frank.goodnight(at)att.ne
Guest

Posted: Fri Aug 20, 2010 6:01 am Post subject: 2-stroke muffler weak area

Hi ,

  

 Tie wire , the wire that is is used to tie the rebar togeather when building ,comes in small rolls ,and can be bought

 at Home Depot or Lows. great for gas welding, and lots of other useful things.

  

 Frank



 

   From: ropermike <ropermike2002(at)yahoo.com>

To: kolb-list(at)matronics.com

Sent: Fri, August 20, 2010 8:11:24 AM

Subject: Re: 2-stroke muffler weak area



--> Kolb-List message posted by: "ropermike" <ropermike2002(at)yahoo.com (ropermike2002(at)yahoo.com)>



I have welded cracks in mine several times. I had to drill small hole at both ends of the crack and weld it with a torch and bailing wire. A friend of mine had a muffler shop and he used bailing wire all the time. The challenge is finding a piece of bailing wire that is not rusted. Of coarse the crack has to be buffed clean and I let it cool slowly after welding.



--------

The next best thing to playing and  winning is playing and losing!...Mike Hillger





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 [quote][b]

Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Fri Aug 20, 2010 12:46 pm Post subject: Re: 2-stroke muffler weak area

I had decided a long time ago that I was the list cheapskate, but I guess not. Gas welding rod is not free, but I never worried about spending what little it costs to just go and buy the real thing.



Besides, I don't have any wire coat hangers, I threw em' all away years ago. All they ever did was commit perverted acts among themselves in the darkness of the closet. You could tell what they had been up to by the huge, tangled wad they would always be in every time you wanted one...



Richard Pike

MKIII N420P (420ldPoops)

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