Topic: How can I patch holes in stock exhaust pipe?

[cb]

I have a 1971 CB500 K0 that has the original exhaust pipes.  Three of them are in good shape, but number one has some holes from rust.
It looks like it has been welded in the past.  Is welding a good option for patching holes, or is there a better way?
Thank you for any advice you have to offer.

[lakerh8r]

I have the same issue with my 750 K0. Someone patched the #2 pipe with some kind of putty years ago. I changed out all wiring, coils, starter switch, rebuilt starter motor, rebuilt solenoid, de-rusted tank, rebuilt carbs, etc (couldn't do it without H-man's book!). Finally got it started only to have the #2 pipe blow black soot and exhaust through rust holes near the footpeg. In the process of removing all pipes for welding repair if feasible. I hate to pay $1500 for a new set of reproduction pipes. 

[RAFster122s]

Problem with trying to weld rusty pipes is the metal is being eaten away from the inside...so getting it clean is one challenge and the second is the hole is much larger than it appears after you cut out the thin metal in the area surrounding the hole.  Refer to first reason... The material being thin is difficult to do without blowing through where you try to patch.  Just a spiral that many don't have the skill to overcome.  Also, the flux on the inside from the weld will accelerate corrosion.  If it is starting to go, there will be more to come in not too long if it goes as usual.  Paying someone to patch your pipes is going to get expensive...better to save your dollars and make the plunge.  Would ceramic coating the inside of a new set of Yamina pipes be feasible without damaging the pipes...that could make them last longer.

Too bad no one has come up with inexpensive ways to replicate a set quickly for these bikes that could be powdercoated mufflers or ceramic-coated pipes.

[calj737]

I'm not sure what "flux" RAF is referring to from welding, but yes, welding them can be done. If they're chromed, the welding will damage the chrome around the weld and its very likely the weld will crack at some point due to the differences in the weld filler metal and the base metal of the exhaust. It may at least buy you some time...

TIG welding them is a better way to repair them as it allows you to control the heat more, and the filler metal is softer than MIG wire (MIG is what most people use to do DIY repairs on exhausts). I strongly suggest you remove the pipe from the bike to have it welded. This protects the bike's electronics from damage, and it will actually weld better if the hole is being worked from above, than below.

As crazy as it sounds, use stainless filler wire (308 works well). Its much softer, melts at a lower heat than 70S-2, and is corrosion resistant in itself. It will also not show as badly as 70S-2 when done.

[Gordon]

Once you get in there and really clean things out to see just how much area you're gonna have to replace, you'll probably end up with a pipe that's stock on the top half and all patch on the bottom half.  If you only do the spots that are currently showing all the way through you'll most likely have a very labor-intensive but temporary fix.  And if one has holes how far behind are the other three? 

[Bodi]

I've tried repairing them and had poor results. As said the holes are just the tip of the rust iceberg, the whole bottom where foul water collects gets paper thin. Hiring a good shop for welding in a complete bottom and making it look decent will cost like a new muffler. This is not a job to learn thin sheet tig welding on.
I would patch it with muffler tape and start saving for a new (or good used) muffler set.

[Stev-o]

I have a set of 341's that came to me with welded patches and they look like crap.

Not sure if I will ever use them, maybe if I piece together that spare frame I have.

Save your dollars and buy a nice repop set, worth their weight in chrome!

Quadruple exhaust!

http://www.ebay.com/itm/M-TEC-Chukyo-No-Number-Quadruple-Exhaust-System-HONDA-CB750K-/152337450631?hash=item2378050687:g:sjcAAOSwENxXmcrE&vxp=mtr

[rocket johnny]

   i use j b weld

[Johnie]

Small holes I have used JB Weld with great results. Then I cover it with chrome tape.