Fin repair

htown16 · Jun 5, 2014

I have a broken fin I need to get repaired. Top fin on the cylinder barrel. Came to me that way, looks like someone tried to pry the head off.
I my looking for a shop to do the work. Any tips I should pass on to them? What type of metal are the fins?

russhud · Jun 5, 2014

I had mine brazed by a local welder, turned out great and only cost $30 or so. It's cast iron, the welder preheats the barrel to get it up to temperature, then brazes the fin back on and lets it cool to keep it from cracking. I've also seen guys TIG weld cast iron fins on using a piston ring for filler metal. Seems to be a pretty good method.

DogT · Jun 5, 2014

I'm sure any good welder can do it. I had mine done when I sent it in to Memphis Motor Werks for a head job. I can hardly tell where it was broke.

1up3down · Jun 5, 2014

nobody believes this when I tell them, but I had a piece of fin broken off that I stuck back on with JB Weld

that was 13 years ago and it is still there doing its job

1up3down · Jun 5, 2014

nobody believes this when I tell them, but I had a piece of fin broken off that I stuck back on with JB Weld

did not heat the motor up, just cleaned the fin and cylinder area and pasted it back on

that was 13 years ago and it is still there doing its job

john robert bould · Jun 6, 2014

Cast iron rod, prep the joint, heat the area, weld on the the fin..THEN KEEP A TOUCH PLAYING ALONG THE WELD, GRADUALY REDUCE THE HEAT Otherwise it will crack again..done a few so i know it works... :wink:

sportsroof · Jun 6, 2014

Mine had fins broken on the head and barrels when I bought it. I used a Mig to fix the barrels (iron) and yes, I know the 'weld' is probably as rubbish as it gets but 16 years on they are still there and not noticeable. I can't even remember now how I fixed the head (ally) fins on, I recall I had to make some to replace missing parts but how did I fix them on? Have to go have a look but I know I didn't let anyone else do it for me so must have been a 'shed' repair and again, still there.
Cheers, Martin

Diablouph · Jun 11, 2014

1up3down said:
nobody believes this when I tell them, but I had a piece of fin broken off that I stuck back on with JB Weld

did not heat the motor up, just cleaned the fin and cylinder area and pasted it back on

that was 13 years ago and it is still there doing its job

Your right. Let's see some photos

Hobot · Jun 11, 2014

Humpf how's it feel to not be believed 1up/3dn. I made a thumb size fin out of nothing but JBW. It lasted through Peels tough trials and trails. Can take a few days to really harden up rigid and will be slightly soft once at full heat but so undetectable painted I knocked it off once handling it so had to JBW back on again. The iron putty in a tube stuff might be better and stiffer for this use. Muggy welding supply has gas touch rods for cast iron DIY repairs if ya can make up a fin section of course.

Diablouph · Jun 11, 2014

hobot said:
Humpf how's it feel to not be believed 1up/3dn. I made a thumb size fin out of nothing but JBW. It lasted through Peels tough trials and trails. Can take a few days to really harden up rigid and will be slightly soft once at full heat but so undetectable painted I knocked it off once handling it so had to JBW back on again. The iron putty in a tube stuff might be better and stiffer for this use. Muggy welding supply has gas touch rods for cast iron DIY repairs if ya can make up a fin section of course.

Trust, but verify.

htown16 · Jun 11, 2014

Yes, I have the fin section and fortunately it is the one on top so easy access.

bwolfie · Jun 11, 2014

I have repaired a bunch of fins. The first few I Tig welded with steel filler rod,
and kept a torch handy to keep heat in it and a slow cool down.

Recently I aquired a large spool of MIG wire for cast iron. High nickle content.
I did some cast repairs using it as the filler with the Tig, much bueno!
No need to keep the heat in it. The spool is 40 pounds, so I have a lifetime supply of it.

Hobot · Jun 11, 2014

In Peel's case right before putting barrel on it was on carpet next to bike and I turned around to hear the thunk/clink. JBW held it on fine AFTER it REALLY set up, OVER days or the Heat of the engine softens it so vibes can shake off. Held fine Until a poor grade flamering from AN blew out oil drain hole so explosive gas jets hit the fin and literally blew it away and almost fuel line too. Weld or braze the piece back on or likely loose it down the road.

mikegray660 · Jun 11, 2014

JB weld may work, but i'm in the camp of do it right and do it once

if you have the fin its an easy task for a good welder (even if you don't a good shop can fix it)

call Cliff at british USA/ Gulf coast BMW and ask him to point you in the direction of a good welder/shop (they may do it there) - he's got lots of brit bikes and knows his stuff

htown16 said:
Yes, I have the fin section and fortunately it is the one on top so easy access.

Hobot · Jun 11, 2014

Getting stuff to welder is a hassle to me travel to other things matching shop's. Might compromise and tack weld on adequately then JBW disquise paint and forgetabout it. Still hoping to talk someone into reporting on this DIY.

randy@randyjanowitz.com
https://www.youtube.com/results?search_ ... +cast+iron

Fin repair

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