Broken cooling fin...motorcycle cylinder head

welder689 · Feb 12, 2007

I've replaced broken fins before, but I've always TIG-welded the new fins on because I could get to them easily. Never had a problem.

A customer wants me to give him a quote on a repair job. It's an old British bike. It has a fin broken off, but it's between two other fins. To TIG weld a replacement back on, I'd have to cut off (with a die grinder/cutting wheel) two other good fins and then weld them back on after replacing the missing fin.

I'm wondering...would it be possible to make a new fin, and BRAZE it on without cutting off the other good fins so I could get at it?

Naturally, the head will be removed from the motorcycle first.

It's an old BSA Gold Star from the 50's...not even sure what the head material is...cast iron or aluminum.

Any and all input appreciated.

SLOEIT · Feb 12, 2007

Cast Iron...maybe
Al...No

Although with the heat input required to braze, id make sure to have the head surfaced to correct any warpage from the brazing process.

nK

welder689 · Feb 12, 2007

SLOEIT,

So...you're thinking I should do what I know will work? Cut off the two fins that are in the way and use TIG?

KenS · Feb 12, 2007

I think that my first choice would be to braze the broken one without messing up any more of them. Each job has a potential to be screwed up and by cutting for room to fix one you're creating two potential failures.

No comment on your skill level intended - it's just the way I look at things - :If it ain't broke, don't fix it" You know.

Whether it's cast iron (probably) or aluminum, preheat to about 400 degrees before starting to braze or weld.

Ignore the inevitable suggestion to use epoxy, as in JB Weld. They'll never survive the britbike vibes.

Limy Sami · Feb 12, 2007

Intresting problem 689, just my 2 cents, by way of a warning.
If it's a genuine Gold Star AKA Gold Bar, and owned by / going to be sold to a Gold Bar nut, be prepared for a lot of what I call the buggeration factor, as they tend to be some of the worst rivet counters in the business and capable of picking holes in the tinyest of details.

Genuine gold bar single from the 50's? it should be alloy head.

Best of luck. Sami..... (you may need it!)

pistonskirt · Feb 12, 2007

If the head is alluminium I just build them up with weld, providing there is sufficient space between the two adjoining fins to accomodate the gas cup, the first few runs will be troublesome and need grinding back before the next run as the crap is drawn out of the parent metal. A bit of careful fettling with a sanding disk to restore the thickness & shape often followed by bead blasting to achieve a similar patina can result in a near invisible repair.

If the fin spacing is too close machine off the fin above or below the broken one just sufficiently to allow welding the original then build up both fins alternating the welding between the two.

If it's cast iron.....good luck.....I have only ever achieved a half decent result by stick welding a piece back in.....sand blast first then use LOTS of pre & post heat.

regards

Brian

matteo · Mar 1, 2007

having owned four or five bsa gold stars, i can
tell you for sure that the head is alloy, i have never seen a cast iron "goldie",i would try to build it up first, if it doesn't work, then go for cutting fins,and oh yes prepare yourself for
a bunch of crap from the owner, present day owners think that they are on a devine mission
from heaven, matteo

Limy Sami · Mar 1, 2007

Thanks matteo, reassuring to know my memorey's not THAT far gone, I like your definition of gold bar owners............ ever come across the present day Vincent-ites?............ they're convinced that god consults them before he even goes for a dump,

........ I lost the will to live with that lot a long time ago.

And my nephew (bless him,- the little bugger

) calls ME a sad old git,....... I tell him he doesn't know the half of it.

Take care. Sami.

stephen thomas · Mar 2, 2007

..and they sound so good!

http://www.youtube.com/watch?v=p2WEBzPwTs0

(buddy of mine gives one some stick)

smt

matteo · Mar 6, 2007

limy-sami, yeah i know what you are saying about
vincent owners, i took a shadow for a ride, was
going to buy it, at about after crossing a train
track, it went into a "knee-slapper" scared the
crap out of me!! the owner thought i was being
"picky" he said it was part of owning a vincent,
talk about strange ideas! my 750 yamaha goes down
the road straight as an arrow! the "goldies" were fun machine in their day, but it is long
gone!! matteo

SLOEIT · Mar 8, 2007

I had an idea...

What about clamping a mold around the broken off fin, and pouring aluminum into the mold, then finish machining to size.

Probably would have to preheat the block, but seems like it would work...

nK

matteo · Mar 23, 2007

in new zealand, there is a fellow that makes
noton manz replcas, in his catalog, he lists
fins, that are to be welded in place of broken
fins on norton cyl heads, maybee that is what
you need in stead of trying to build up the
whole fin!! his name is "mac" something or other
and he advertises on the "net" worth the effort
of finding him matteo

Michael Moore · Mar 24, 2007

Probably McIntosh Racing:

http://www.mcintoshracing.com/

cheers,
Michael

matteo · Mar 24, 2007

yeah, thats it! i owned a manx several years ago, and he was the one to go to for parts! he
can make you an entire manx out of his parts room
plus he is a nice guy! in his catalog, he has
"fins" to be used if you bust one or two off!
you can view his catalog on line matteo

Michael Moore · Mar 24, 2007

I had an outing on a friend's Garden Gate at one of the AHRMA nationals at Laguna Seca some years ago.

http://www.eurospares.com/harold.jpg

cheers,
Michael

Search

Largest Manufacturing Technology Community on the Web

Search

Broken cooling fin...motorcycle cylinder head

welder689

Aluminum

SLOEIT

Cast Iron

welder689

Aluminum

KenS

Cast Iron

Limy Sami

Diamond

pistonskirt

Hot Rolled

matteo

Aluminum

Limy Sami

Diamond

stephen thomas

Diamond

matteo

Aluminum

SLOEIT

Cast Iron

matteo

Aluminum

Michael Moore

Titanium

matteo

Aluminum

Michael Moore

Titanium

Similar threads