Author Topic: Cracked Fork leg  (Read 2560 times)

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Offline Porscheguy912

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Cracked Fork leg
« on: July 19, 2009, 06:57:37 PM »
So when changing my fork seals i noticed a few things.

#1: My right tube has a crack in the upper seal retaining wall!
So about this..... Can I TIG weld it and grind it smooth? In the pics you can see that the crack does not go below into the tube area, just the thin part on top so im guessing that at the point it is cracked its not to structurally important.

#2: I noticed that the oil seals in the tube weren't really oil seals im used to seeing.
They do not have the metal collar ring so they are bendy and kinda like big square bodied O-rings.
They also do not have the inner lip and spring that most do; just a few ridges that "could" help seal.

It appears the PO was in there before because the bores were all scraped to hell from a screw driver too, so i guess i wouldnt put it past him to have over tightened them in a vise, cracked the tube and then installed the wrong seals. Funny thing is that the one that is cracked is the one that was not leaking.

I have a few guys on here that i can get a new used one from, but i am curious if i should try to fix it.
Are they aluminium, magnesium or some alloy there of?

Thanks!
1978 CB750F
« Last Edit: July 20, 2009, 09:39:18 AM by Porscheguy912 »
Current: 1978 CB750F3
Past: 1974 CB550K

Offline Porscheguy912

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Re: Cracked Fork leg
« Reply #1 on: July 19, 2009, 06:58:47 PM »
Seals, New on right, old on left.
« Last Edit: July 20, 2009, 09:39:48 AM by Porscheguy912 »
Current: 1978 CB750F3
Past: 1974 CB550K

Offline Porscheguy912

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Re: Cracked Fork leg
« Reply #2 on: July 20, 2009, 09:13:16 AM »
Mid day bump......
« Last Edit: July 20, 2009, 09:40:12 AM by Porscheguy912 »
Current: 1978 CB750F3
Past: 1974 CB550K

Offline 754

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Re: Cracked Fork tube
« Reply #3 on: July 20, 2009, 09:31:57 AM »
That is your fork leg, or lower leg, or slider.

The forktube is the shiny one, that looks like... well a piece of tubing..

 You can TIG it, be VERY clean, probably egg a bit, but seal will still work. They are cast aluminum. If they are all gouged, might not be worth doing. Unless you can get it welded cheap, and it is in otherwise good shape, it may not be worth fixing. check it for wear to the tube.

 Seals are rubber over metal, some cheap types of seal are less coated on the outsides, CR seals come to mind.
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline Porscheguy912

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Re: Cracked Fork leg
« Reply #4 on: July 20, 2009, 09:38:46 AM »
That is your fork leg, or lower leg, or slider.

The forktube is the shiny one, that looks like... well a piece of tubing..

 You can TIG it, be VERY clean, probably egg a bit, but seal will still work. They are cast aluminum. If they are all gouged, might not be worth doing. Unless you can get it welded cheap, and it is in otherwise good shape, it may not be worth fixing. check it for wear to the tube.

 Seals are rubber over metal, some cheap types of seal are less coated on the outsides, CR seals come to mind.

I can get it welded for free by my friend so it will be as cheap as a sixer of PBR.
Yes it is the leg i guess. Perhaps i will change the title of the post.
Thanks for the info  :)
« Last Edit: July 20, 2009, 09:40:28 AM by Porscheguy912 »
Current: 1978 CB750F3
Past: 1974 CB550K

Offline bryanj

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Re: Cracked Fork leg
« Reply #5 on: July 21, 2009, 10:13:20 PM »
Those seals were an aftermarket idea to try and stop leaks that didnt work. You need to fill in any gouges in the bore the new seals push in to or oil will leak arround the outside
Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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technojock

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Re: Cracked Fork leg
« Reply #6 on: July 23, 2009, 01:50:41 AM »
You can weld it up but it'll never be right.  You're far better off looking for a replacement.

Tony

Offline Porscheguy912

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Re: Cracked Fork leg
« Reply #7 on: July 23, 2009, 06:09:40 PM »
I fixed it.
TIG welded and  ground smooth and dressed out like new.
It Can be done!

here are the pics.
I like the look of the upper ribs paint free. It matches my sanded engine fins.
I will fill in the lines with new black paint too.
Thanks for the encouragement 754.
Current: 1978 CB750F3
Past: 1974 CB550K

Offline Porscheguy912

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Re: Cracked Fork leg
« Reply #8 on: July 23, 2009, 06:10:43 PM »
more pics:
Current: 1978 CB750F3
Past: 1974 CB550K

Offline honda750k

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Re: Cracked Fork leg
« Reply #9 on: July 23, 2009, 06:14:41 PM »
Looks really nice to me. good work.
These bikes dont die, they hibernate until the right person wakes them up again.

Offline 754

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Re: Cracked Fork leg
« Reply #10 on: July 23, 2009, 06:15:19 PM »
Cool.. ;D

 I want Tony to be the insurance adjuster if I ever smash my bike...
 as long as I get to buy it back.. ;D
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline Porscheguy912

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Re: Cracked Fork leg
« Reply #11 on: July 23, 2009, 06:23:38 PM »
BTW i forgot to take pics of the inside when i was done grinding and buffing it.
I was too excited to get it back together.

I'm just going to pray that they dont leak!
But like i said the one that was leaking was not the one that was cracked so we'll see.

Current: 1978 CB750F3
Past: 1974 CB550K

Offline Porscheguy912

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Re: Cracked Fork leg
« Reply #12 on: February 14, 2010, 08:47:46 PM »
BTW:
It did leak.

I got a new leg from BigBob and had it back together in an hour.

Moral: Dont bother welding it unless spares are impossible to find....

J.
Current: 1978 CB750F3
Past: 1974 CB550K