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Silencer Flange Cracked-Fixable? Pics inside.

biglou

#1
I put this here just to make sure Rich sees it, and maybe SFO and Cujet, etc. This is the Big Gun silencer off my 426. The mount flange has separated from the can insert. It appears as though I could weld it on the inside around the lip. Any thoughts? Can it be done? I haven't removed the rivets yet. Going riding tomorrow so I threw the stocker back on. I noticed the outer wrapping of the packing coming out some time ago. Guess I should have investigated that a little more thoroughly. As it turns out, I burned right through my right number plate at DirtWeek with this exhaust leak!
Pics:
Outside of can.
Inside of can.
Bottom inside view.
 

XRpredator

AssClown SuperPowers
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#2
Have you talked to Big Gun about it to see what they say? I wonder (even if they wouldn't help you out) if they may want to know about such a failure of their part. It would seem to me that you could drill out the rivets and then TIG that sucker back together. Shouldn't affect anything, since all it really does is hold the can on.
 

biglou

#3
Ah, I forgot to mention, I've also emailed Big Gun along with links to the pics to see what they say.
 

Treejumper

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#4
I'm with Pred, contact Big Gun first then if they wont do anything you can easily weld that shut.
 

biglou

#5
ok, drilled out the rivets, and I'm sure I can weld this from the inside. I also repacked it tight with Performax. About 1/4 of the packing around that end was burnt up and missing. The nice thing about this silencer is the perforated tube that runs through the center of the can is not connected at either end. Made repacking it nice and tight a breeze.

On another note, I tried to pull the dent out of the curve in the head pipe by heating it and then putting an ice cube on it. But, no luck there. I'll have to wait until Monday at work to weld up the mid pipe. Should be no problem <---famous last words! lol
 

Rich Rohrich

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#6
I'm sure it can be welded but I'd want to know what caused it to crack in the first place to keep it from happening again. I'm sure Mike Young would want to know the same thing so it's worth talking to Big Gun first.
 

LJW

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#7
Originally posted by Rich Rohrich
...what caused it to crack in the first place to keep it from happening again.
The part was formed with insufficient bend radius. An aluminum part used in a hot, high vibration application should have a bend radius equal to AT LEAST 4 times the material thickness. The sharp corner shown in the photos almost guarantees a failure.
 

Philip

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#8
Originally posted by BigLou
Should be no problem <---famous last words! lol
Cajuns famous last words "watch dis" :laugh:

Lou I think like everyone else about the welding but any idea on what caused it. It doesn't seem like corrosion so I wonder what caused the failure. :think:
 

biglou

#9
Not sure what caused it to start cracking, but it has been progressive. It started down in Texas when riding after the Dallas SX. I started to notice the outer packing wrap unraveling and coming out the bottom of the front of the can. I didn't notice the crack, but thought it was just coming out a seam. It unravelled pretty regularly for a while, then stopped. I did lay it down on the right side twice at Cooperland in that big, loamy right hander, two turns before the big step up. That may have been when I burned through the side plate as I got stuck for a short time with my right leg in the rut and pinned under the bike. As for root cause, LJW's theory sounds pretty good to me. Tight bend, high vibration, etc.

On another note, seems my email addy that I sent the message to BG from has stopped working for the moment, so that explains the lack of response from them. I just resent the info from work, and I am hanging onto the pipe until I hear from them. No big rush, I've got the stock pipe back on. The difference, btw, is amazing. The stocker has noticeably more low end, right off idle, but runs out on top much quicker. I actually overjumped a couple times Sunday from the increased low-rpm pull, and was playing "wheelie king" while practicing starts! It's all a familiarity issue now, so I want my Big Gun back! :)
 
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#10
If its aluminum I got these awesome brazing rods called like alumilite or someting. You can brase aluminum with a propane torch. I have to check the melt temp though. The stuff is stronger than the aluminum so you could build up a nice radious with it. Is there any reason you cant just weld or brase it to the outer can as well?
Yeah, it looks to thin and sharp curved there. Also check your mounting to the sub frame, it should be unstressed, you should not have to force weight on it to line up the bolt hole, is should be mounted with a polyurathane bushing to soak up some of the vibes too.
 

biglou

#11
I just got a reply from BG. If they have a midpipe "laying around", they're gonna hook me up. Sweet! Also, if we wind up welding it, we were going to braze it or silver solder it. For stuff this thin, I defer to our maint. supervisor. I can hack thick steel together, but I'd blow some serious holes in this thing! Also, I wouldn't weld to the can. Need to get it off for repacking ease. It could probably be done, but it would be a major pain unless both ends still came off.
 

Rich Rohrich

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#12
Originally posted by LJW


The part was formed with insufficient bend radius. An aluminum part used in a hot, high vibration application should have a bend radius equal to AT LEAST 4 times the material thickness. The sharp corner shown in the photos almost guarantees a failure.
Given the severity of the crack that sure makes the most sense.

Like Carroll Smith used to say, "materials don't fail people who design with them do". Good catch LJW :thumb: :worship: