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Fork yoke top nut issue


smarty156
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Having fixed my fork yokes and replaced head bearings etc, I went to put everything back and have hit an issue.

I ordered a new top nut as the previous owner had severely damaged the old one. However, despite being the correct GasGas part and having now ordered 2 from different places, the top nut is wrong. Basically it's about 2mm longer than the one that came out which means it hits the retaining nut before it tightens down onto the upper fork yoke.

I've taken a photo side by side with old versus new so you can see. I've measured the space between the retaining nut and the top yoke and it's about 15mm so there's no way the new nut can work and there's nothing you can do to make it more.

What gives? Suggestions?

20200619_114840.jpg

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It doesn't sound right, but I don't have a gas gas so I can't picture all of the related parts. 

Check the size of the bearings and any spacers and seals against the old ones and check they are seated correctly on the stem and in the headstock. As the old ones may have been incorrect also compare to the parts manual.

Any thing too thick or not fully seated could make the retaining nut sit higher. 

Edited by totty79
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So the top yoke sits on top of this locking nut (the raised bit in the centre sits inside the hole in the yoke to help centre it). The top nut then goes into the stem and should tighten against the yoke and hold it tight to the locking nut. However, as the locking nut is too long it's coming up against the raised centre part of the locking nut before it tightens down onto the yoke.

There's nothing you can adjust as the thickness of the yoke is what determines how far the nut can be threaded down.

The attached pic is the old one before I removed it. Looking at the old top nut it looks like this was filed down to the right length too. All very weird. 

20200419_150103.jpg

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I've replaced the spindle as well as upper and lower fork yoke with new ones.

The length of the spindle doesn't make a difference. The depth of the hole is governed by the thickness of the fork yoke.

Edited by smarty156
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Strange system with part of the top nut passing through the yoke.

What is the grove around it and the bolt marks on the old one all about? It looks like the yolk may be fixed to the top nut rather than clamped between the lock nut and the top nut as you'd normally expect. Alternatively a spacer to effectively increase the thickness of the yolk may be missing.

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My understanding is that the top nut threads onto the spindle and draws the top yoke to the spindle nut (?). If the top nut is bottoming out before it engages the yoke, it seems that your only recourse is to remove some material from the top nut, or shim the gap between the top nut flange and the yoke (with some large washers perhaps). I can't recall what the suggested torque is for the top nut, but my concern would be that you may not engage sufficient threads on the spindle if the spindle isn't protruding sufficiently.

Is your top tapered bearing race driven sufficiently down into the steering head/frame (i.e., what would be immediately under the opaque nylon dust cap)? I think the race should be flush with the frame.

Edited by d2w
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Yes, your first sentence is correct.

Yes it seems the only option is to shorten the top nut by around 2mm. Which I can get done and there's plenty of thread so that shouldn't be an issue. 

It's just that everything is brand new with correct parts so why doesn't it fit? If they are correct parts then every Gas Gas must have the same issue.

As for the bearing race, that's all fine but even if it wasn't it would only affect the amount of thread available on the stem to screw the nut onto. The top nut would still hit the locking nut as the locking nut sits snug under the top yoke and the top yoke (which is genuine GasGas and new) is a certain thickness. There is nothing other than shortening the top nut or putting a washer under the top nut head (between head and top yoke) that can be changed. There's no washer shown on the parts diagram and very little space for one.

Surely I'm missing something?

Can anyone else with a roughly 2014 GasGas remove the top nut and measure how long it is and check if there's a washer under the head of the top nut for me please? There must be an explanation.

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So I've just been out to the garage and had a brain wave while looking at it.

I'd put it back together the way it was when I took it apart (as per previous photo with the top yoke removed). However, what if that's not how it should have been?

So, the plastic cover has a hole slightly larger than the spindle. What if the locking nut should be up the other way? So I tried it, the locking nut raised bit then sits inside the hole in the plastic cover and the top yoke sits on top of the flat part of the locking nut. Therefore when you screw the top nut in it can't hit the raised part of the locking nut and WILL screw down onto the top yoke!

Problem solved! 

So yet again the previous owner completely messed things up and cut the top nut down to bodge it to fit.

Anyone know the torque for the locking nut? Want to get it right.

Here's a pic of how it should be.

The locking nut being inside the top yoke centres it.

20200619_175014.jpg

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