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Steel fork yoke modifying for smaller fork diameter

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MilesNurserie...
L Plate Warrior



Joined: 17 Jan 2023
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PostPosted: 12:12 - 17 Jan 2023    Post subject: Steel fork yoke modifying for smaller fork diameter Reply with quote

Can anyone advise please?

I have a Suzuki GT550 with 32mm diameter forks. These were one year only. The top and bottom yokes are nearly impossible to find now.

Yokes for 34mm forks are common. Is it an option to cut away material (steel) either side of the slot that the pinch bolt goes through so as the clamp will work on the smaller fork leg? Or is it not a safe option?

I am only interested in the engineering and safety side of this please.

Thanks in advance
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Nobby the Bastard
Harley Gaydar



Joined: 16 Aug 2013
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PostPosted: 12:23 - 17 Jan 2023    Post subject: Reply with quote

It sounds a completely idiotic idea to me.
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MarJay
But it's British!



Joined: 15 Sep 2003
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PostPosted: 12:42 - 17 Jan 2023    Post subject: Reply with quote

How to break your yoke in one easy lesson. It would be easier to create a sleeve to put into the top yoke, or better yet swap an entire front end. Larger diameter forks would be better anyway.
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 14:22 - 17 Jan 2023    Post subject: Reply with quote

You'd probably be safer to shim it. You're only looking at a 1mm thick shim.
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Evil Hans
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Joined: 08 Nov 2015
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PostPosted: 14:35 - 17 Jan 2023    Post subject: Reply with quote

If you do it that way, it'll clamp it up but it won't actually be gripping it around the whole circumference as the hole will still have the wrong radius for the fork. Sounds like a terrible idea.

Shim it.
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virus
World Chat Champion



Joined: 17 Aug 2006
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PostPosted: 18:48 - 17 Jan 2023    Post subject: Reply with quote

The proper way to do it would be to replace the yoke set to match, id be suprised if they stems were that different in length and headstock bearing sizes if its 2 old Zooks of the same model (youd have to check though)

Otherwise I would always be going for a shim over filling the land out of the yoke to clamp, this join is responsible for holding up the entire front end, its not just done slightly oversize exhaust clamp.

Buy yokes to suit or some shim steel from an engineering supplier.

Cheers
John
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Robby
Dirty Old Man



Joined: 16 May 2002
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PostPosted: 13:40 - 18 Jan 2023    Post subject: Reply with quote

Can you fit the whole front end from a bike with 34mm forks?

Even with shimming (which I don't particularly like) you may end up with the other end of the forks being in the wrong position. You're working off the assumption that the yoke is the same with the same hole centres, just cut one mm bigger.

It's a job for very careful measuring. Then, if the part will work, the right way to do it would be for an engineering shop to build up the hole with weld then bore it to 32mm.

A whole front end swap is probably cheaper.
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WD Forte
World Chat Champion



Joined: 17 Jun 2010
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PostPosted: 19:31 - 18 Jan 2023    Post subject: Re: Steel fork yoke modifying for smaller fork diameter Reply with quote

MilesNurseries2013 wrote:
Or is it not a safe option?

I am only interested in the engineering and safety side of this please.

Thanks in advance


It is NOT a safe option!

Take the above advice and use matching forks and yokes
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Islander
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Joined: 05 Aug 2012
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PostPosted: 01:20 - 19 Jan 2023    Post subject: Reply with quote

If you are going to consider shimming the gap, it might be worth using some Loctite bearing retainer between the shim and the stanchion. Once it's fully cured its amazingly strong stuff and should ensure that the shim doesn't move.
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