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Author Topic: Will A Fin Put Up With Bending twice?  (Read 565 times)

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tooseevee

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on: May 12, 2018, 05:48:28 pm
            When I pulled the head off the '08 AVL to send off to Ace those many years ago, I had to "tap" it up at 4 points on the compass with a piece of wood and my little 4 pound "tapper" until it finally popped loose from the cylinder.

            The corner at the right rear of the lower fin deformed upward maybe a 1/4 inch. I've never had to pound a bent aluminum fin back in shape before so I have to ask opinions on whether it should just bend back OK or just leave it.

             It never bothered me before, but I saw it in the right light a couple days ago and now, of course, it's all I see when I walk past the bike.     
2008 AVL Classic.Extensive head work by Ace.Ace canister/TM32/Ace manifold.Small open bottle/hot tube removed.Pertronix Coil.Bobber seat.Fed mandates removed.Battery in right side case.Decomp&all doodads removed.'30s Lucas taillight/7" headlight.


ace.cafe

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Reply #1 on: May 12, 2018, 09:23:26 pm
Leave it as it is.


Bilgemaster

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Reply #2 on: May 13, 2018, 04:26:39 am
Yeah. It's not a defect, it's a feature. You have one of the few "Flared Fin" factory heads that afford enhanced "Venturi Vomoblastification", as the guys in Marketing say.
« Last Edit: May 14, 2018, 07:00:24 am by Bilgemaster »
So badass my Enfield's actually illegal in India.


tooseevee

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Reply #3 on: May 13, 2018, 06:34:46 am
Yeah. It's not a defect, it's a feature. You have one of the few "Flared Fin" factory heads that afford enhanced "Venturi Vomoblastification", as the guys in Marketing say.

             What I'm really concerned about is that the disruption of airflow over that bent upward section of fin could unbalance the bike at high speed. I could be forced out of my intended line and directly into an oncoming Kenworth or White Freightliner  :) Godonlyknows how unstable the bike might become above a certain speed  ;) ;)
2008 AVL Classic.Extensive head work by Ace.Ace canister/TM32/Ace manifold.Small open bottle/hot tube removed.Pertronix Coil.Bobber seat.Fed mandates removed.Battery in right side case.Decomp&all doodads removed.'30s Lucas taillight/7" headlight.


Mick Bailey

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Reply #4 on: May 13, 2018, 11:34:13 am
I've bent back many fins on different bikes with complete success. The caveat is there cannot be any cracking, otherwise the fin will most likely break off. I use an oxy-propane torch, spoon-type tyre lever and a bar of soap. The fin has soap rubbed on it to give an indication of temperature. It turns brown (then black) when the maximum temperature for the aluminium alloy is reached. I run the bike up to temperature, rub on soap and then using a small angled nozzle kept on the move I heat the fin where it needs to bend whilst applying very gentle pressure with my tyre lever. The fin will bend like Uri Geller bending a spoon. It doesn't need much heat or much force. If in doubt leave it alone and certainly don't try to bend it cold; the metal work-hardens where it's bent and when you try to straighten it the fin will bend somewhere else. Or break along the original bend.


tooseevee

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Reply #5 on: May 13, 2018, 01:15:32 pm
I've bent back many fins on different bikes with complete success. The caveat is there cannot be any cracking, otherwise the fin will most likely break off. I use an oxy-propane torch, spoon-type tyre lever and a bar of soap. The fin has soap rubbed on it to give an indication of temperature. It turns brown (then black) when the maximum temperature for the aluminium alloy is reached. I run the bike up to temperature, rub on soap and then using a small angled nozzle kept on the move I heat the fin where it needs to bend whilst applying very gentle pressure with my tyre lever. The fin will bend like Uri Geller bending a spoon. It doesn't need much heat or much force. If in doubt leave it alone and certainly don't try to bend it cold; the metal work-hardens where it's bent and when you try to straighten it the fin will bend somewhere else. Or break along the original bend.

           That goes along with all I've learned over the years. You just can't trust metal cold; some might bend once and then break, others you might bend twice, but never three times.

            I can't use heat so I'll leave it. There're just too many hours of detailing (and a carburetor) in that area and I'd never match the finish the factory put on the AVL heads or fix the burned wrinkle-black on the cylinder.

             Thanks, everybody. We'll call it a beauty mark ;)

             
2008 AVL Classic.Extensive head work by Ace.Ace canister/TM32/Ace manifold.Small open bottle/hot tube removed.Pertronix Coil.Bobber seat.Fed mandates removed.Battery in right side case.Decomp&all doodads removed.'30s Lucas taillight/7" headlight.


Adrian II

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Reply #6 on: May 13, 2018, 01:18:30 pm
Quote
Thanks, everybody. We'll call it a beauty mark ;)

Yep, managed to get one of those on the big head, fortunately it's not on the pretty side.

A.
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tooseevee

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Reply #7 on: May 13, 2018, 01:51:40 pm
                      I can't use heat so I'll leave it. There're just too many hours of detailing (and a carburetor) in that area and I'd never match the finish the factory put on the AVL heads or fix the burned wrinkle-black on the cylinder.

             Thanks, everybody. We'll call it a beauty mark ;)
         

            Picture of the bloody bent bastard:
2008 AVL Classic.Extensive head work by Ace.Ace canister/TM32/Ace manifold.Small open bottle/hot tube removed.Pertronix Coil.Bobber seat.Fed mandates removed.Battery in right side case.Decomp&all doodads removed.'30s Lucas taillight/7" headlight.


Arizoni

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Reply #8 on: May 13, 2018, 05:27:54 pm
Marketing would call that bend a,

 "Vortex Stabilizer which enhances aerodynamics at elevated speeds."

Do not frinkle with the Vortex Stabilizer or dire consequences may be experienced.
Jim
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Bilgemaster

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Reply #9 on: May 14, 2018, 07:16:59 am
            Picture of the bloody bent bastard:

Ugh! I see what you mean! That scarcely-perceptible bump ruins everything!...

So badass my Enfield's actually illegal in India.


heloego

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Reply #10 on: May 14, 2018, 07:30:52 am
You just delivered an epiphany.  :o
And all this time I just thought her ears were too big!  ::)
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Adrian II

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Reply #11 on: May 14, 2018, 09:09:24 am
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Picture of the bloody bent bastard:

It's doing an excellent job of distracting attention from the barrel fins around the pushrod tunnels where the casting doesn't quite line up properly.  ;D

A.
Grumpy Brit still seeking 500 AVL Bullet perfection! Will let you know if I get anywhere near...