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  #1  
Old 7th October 2018, 12:46 PM
-alan-'s Avatar
-alan- -alan- is online now
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Motorbike: Blue Bomber & tbc..
Default Fork leg - scratch or cracking ?

Cleaning the right fork lower, spotted this:

Click the image to open in full size.

A sharp edged scratch - or crack - deep enough to catch a thumbnail, and which extends 6-7/8 of the way round the circumference of the tube.

Not a great pic - apologies. Is there any way to confirm if it's a surface scratch, or whether it's something more serious ?

Thanks,
Alan
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  #2  
Old 7th October 2018, 01:00 PM
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KTMkenny KTMkenny is offline
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Default Re: Fork leg - scratch or cracking ?

Jeepers. that looks scary as hell. How would ya get a scratch like that?
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  #3  
Old 7th October 2018, 01:40 PM
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vinnym vinnym is offline
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Default Re: Fork leg - scratch or cracking ?

Looks like a crack dude, Donno how youd get a scratch most of the way around leg
Might be safest option to remove fork and have a look. Id be inclined to try maybe the likes of thinners in the tube to see if it leaks through the possible crack
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  #4  
Old 7th October 2018, 01:44 PM
proto proto is online now
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Default Re: Fork leg - scratch or cracking ?

Is there anything to suggest damage, like a bend somewhere or headstock cracking? I'm guessing that metal is too soft to crack like that. If it was all the way round surely the cracking would have widened with use or leaked something.
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  #5  
Old 7th October 2018, 02:22 PM
johnny b johnny b is online now
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Biker.ie Member No. 5067 from Kildare-ish.
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Default Re: Fork leg - scratch or cracking ?

Is it a bmw?
Is it under warranty?
Can a dealer asses it?
Do you have access to an x-ray machine?


All very real questions.
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  #6  
Old 7th October 2018, 02:52 PM
Seanie Philip Hugo Baron van Zuylen van Nijevelt's Avatar
Seanie Philip Hugo Baron van Zuylen van Nijevelt Seanie Philip Hugo Baron van Zuylen van Nijevelt is offline
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Default Re: Fork leg - scratch or cracking ?

Looks like a crack to me
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  #7  
Old 7th October 2018, 03:18 PM
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KTMkenny KTMkenny is offline
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Default Re: Fork leg - scratch or cracking ?

It may simply be a casting mark.
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  #8  
Old 7th October 2018, 03:42 PM
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allsorts&oddjobs allsorts&oddjobs is online now
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Biker.ie Member No. 9980 from west limerick
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Default Re: Fork leg - scratch or cracking ?

wouldnt chance riding it untill you know for sure anyway, if it is a crack it could be lethal, check another bike the same as it to see if its a casting mark, other than that id say its a crack.
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  #9  
Old 7th October 2018, 03:50 PM
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Default Re: Fork leg - scratch or cracking ?

There's no sign of damage I can see, but its an old machine - and the lowers could have come from another bike.

Originally Posted by johnny b
Is it a bmw?
Is it under warranty?
Can a dealer asses it?
Do you have access to an x-ray machine?

All very real questions.
(i) Johnny - nope, it's an 'Onda.
(ii) It might have been about 40 years ago :)
(iii) That's a possibility
(iv) No, access to any crack detection facilities alas.

Was thinking of taking some wet and dry to it to see how deep it is / whether it'll buff out - or whether there's more afoot here. Is that wise ?
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  #10  
Old 7th October 2018, 03:58 PM
goodbob goodbob is offline
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Default Re: Fork leg - scratch or cracking ?

If it's that old might I suggest that it's time to replace the forks? Metal fatigue?
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  #11  
Old 7th October 2018, 03:59 PM
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Gixxer Gixxer is offline
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Default Re: Fork leg - scratch or cracking ?

Pull on it and see if it spreads.
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  #12  
Old 7th October 2018, 04:10 PM
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allsorts&oddjobs allsorts&oddjobs is online now
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Default Re: Fork leg - scratch or cracking ?

Originally Posted by Gixxer
Pull on it and see if it spreads.
tried that one time and got an awful slap across the face......
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  #13  
Old 7th October 2018, 04:26 PM
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The comb over kid The comb over kid is online now
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Default Re: Fork leg - scratch or cracking ?

Originally Posted by allsorts&oddjobs
tried that one time and got an awful slap across the face......
Was told it would make me go blind! so asked "could i do it till i needed glasses"
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  #14  
Old 7th October 2018, 05:20 PM
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Default Re: Fork leg - scratch or cracking ?

Originally Posted by Gixxer
Pull on it and see if it spreads.
Tried it meself too - couldn't get the crack to open even the least little bit ...

Took to an inch long section of it with some 240 grade wet and dry, and then shined it up a bit with some 1200 grade to see what was beneath:

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Whatever it is doesn't go deep - polishes out easily enough without taking too much aluminium away. Not sure if that proves anything though other than if it is cracking, it's not coming from the inside out
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  #15  
Old 7th October 2018, 05:56 PM
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sidegrinder sidegrinder is offline
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Default Re: Fork leg - scratch or cracking ?

is there even a place you get it x rayed, somewhere that might do non destructive weld testing or something? it could well be a scratch but i know if i was riding that bike id be constantly thinking about it, id just replace it
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  #16  
Old 7th October 2018, 08:36 PM
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Default Re: Fork leg - scratch or cracking ?

Me good eye says its a crack......Bin it and replace. While your at it, give the other fork leg a thouragh inspection and check for similar fractures......better find out now than land on the seat of your arse where the dam thing folds out from under ya....
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  #17  
Old 7th October 2018, 08:56 PM
dePeatrick dePeatrick is offline
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Default Re: Fork leg - scratch or cracking ?

Crack would not polish out, I'd trust it imo.
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  #18  
Old 7th October 2018, 09:30 PM
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Default Re: Fork leg - scratch or cracking ?

Get yourself a crack detection kit, ambersil or rocol are the two i have used.
There's 3 components, a cleaner first, then a dye penetrant and a developer.
Spray on the cleaner first, wipe it off, the the penetrant dye, wipe that off, then the developer will draw any dye out of the crack, if one is there, and will show up stuff you will never see.
By the way, just because it polished out doesn't mean its not a crack, aluminium is tricky that way because its soft and will blend in across a crack.
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  #19  
Old 7th October 2018, 09:32 PM
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Motorbike: Blue Bomber & tbc..
Default Re: Fork leg - scratch or cracking ?

Originally Posted by the landshark
Get yourself a crack detection kit, ambersil or rocol are the two i have used.
There's 3 components, a cleaner first, then a dye penetrant and a developer.
Spray on the cleaner first, wipe it off, the the penetrant dye, wipe that off, then the developer will draw any dye out of the crack, if one is there, and will show up stuff you will never see.
By the way, just because it polished out doesn't mean its not a crack, aluminium is tricky that way because its soft and will blend in across a crack.
Thanks landshark
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  #20  
Old 7th October 2018, 10:01 PM
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galway86 galway86 is offline
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Default Re: Fork leg - scratch or cracking ?

That could have been caused by twisting the fork leg in the triple trees when trying to remove the forks, just a thought? Can't see how else it could be almost all the way around otherwise, even a crack would have to spread to grow like that.
Maybe widening the clamp of the triple tree with a screwdriver , put it too far in to where it was contacting the fork then spun the fork as they lifted or droped ?

Last edited by galway86; 7th October 2018 at 10:09 PM.
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