Broken fin - repairable ?.

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While blasting my barrel I noticed a repaired fin...done in the late '70s and is still crack-free.
 
Yep.

My rolling basket case bike has 3 missing fins that I sacrificed to repair 2 other cylinders a while back.

I've also done heads, using bits of fins from a massive 2-stroke head I have on the shelf. It's still got enough on it to fix about 372 more heads at this rate...
 
I have always been told that welding cast was difficult and that welding cast that had been heated and cooled a number of cycles is even harder. Please cast some illumination on this! TIG? What is the process. I have a cast repair unrelated to motorcycles I need to perform.

TIA,
Russ
 
I did mine using TIG and steel filler rod. No pre heat, allthough would be better.
 
A local welder told me to use nickel rod on old cast. Seemed kinda odd at the time but I respect his work. Ever heard that?
 
Cast iron, being in the same family as steel, stainless and many others, should take well to many tipes of filler materials. I have had excellent results with steel filler. But if you are worried, and have a sacrificial barrel to use. cut up some strips of old fin and use that. Then you know it's the same.
 
Mine had two broken fins under the exhaust nuts, I just cleaned up the broken edge with a file, cut out some mild steel flat to fit and brazed it in, this was while it was still dads bike, it has done 30k miles and fallen off a bench during and earthquake since then and still no signs of cracking. In the past I have also had success joining bits of cast iron back together with 316 tig filler wire and oxy acetylene
 
http://www.muggyweld.com/castiron.html
In the past, cast iron was always difficult to repair: heat the part slowly in an oven, make the weld with a nickel rod, slowly cool the part in an oven--and hope the cast iron would not recrack (it frequently did). Most welders wouldn't even attempt to weld cast iron due to the tempermental nature of such repairs. Fortunately, times have changed. Muggy Weld offers two solutions for cast iron repair: arc electrodes and gas torch rods.
 
Every time I have heated up cast iron to red, it melts like slag. I take it to a pro. Leo at Memphis did mine while he had the head, looks good.

Dave
69S
 
I have repaired plenty of fins,
Stick the barrel in the oven, Have a blow touch ready ,get some one to play the touch over the joint while welding with a stick set and keep the touch on the weld , then drop the barrel into dry fine sand to cool..easy.
 
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