KR-1S.co.uk Forum

Never had to do this before so I thought I had better seek some advice.
I want to remove a stem from a metal bottom yoke & pop a Kr1s stem in.
What's the best way to remove the stem? Its welded in, so do I need to ground the weld back or would I be better off drilling the unwanted stem out?
Its for a Zxr250 front end (many thanks again Charles ) for my Kr1s project.

Andy Bailey has done this and I think it was ground off, but you're best off asking him.

My conversion was a 1S stem, which was pressed out and then bushes made up for the ZXR400 bottom and top yoke.

Hi Howie, you mean a steel yoke?

Yes the answer on all the ones I have done is grind the weld off with an angle grinder. the stem usually pushes out as it is not pressed in.

The KR stem is quite small in diameter so you will likely have to have bushes made up to put the stem into whichever yokes you are using.

The KR stem has a circlip on the bottom so make sure you machine a recess for it to go into, only about 0.5mm diametrical clearance so the thing cannot jump off.

I usually use 0.1 to 0.15mm interference on the stem to bush and about the same into the yoke. This gives an insertion force of about 2 tonnes each way.

I put the bush into the yoke first and then the stem into the yoke and lightly lube the parts. A bit of graphite lube works brilliantly.

Oh on the bush, make sure you put a step on it (so it looks like a top hat) which might mean you have to machine a recess into the yoke. On ZXR 400's the step is already there. I used the H model ones on the KR so I could use RGV Vj22 forks.

You need to make another bush for the top yoke because the hole in the ZXR yoke is much bigger than the KR stem.

Hope this helps

Thanks for that Smithy.

I do mean a steel yoke (sorry, I'm not good with descriptive words). The ZXR250 yokes I have use the same taper bearings as the Kr1/1s so I'm hoping I will not need to bush the stem.

And the only difference I can see between the two stems is the length.

I will be welding the Kr1 stem into the Zxr bottom yoke, so do you think I should remove the clip before welding or just weld over it?

I could be wrong here, as I have not done it myself, but I seem to recall you can use the Zxr250 stem, you just need a small spacer.
I'm sure John-b did it that way, might be worth pinging him a pm?

Howie wrote: And the only difference I can see between the two stems is the length.

I will be welding the Kr1 stem into the Zxr bottom yoke, so do you think I should remove the clip before welding or just weld over it?

Cool I haven't used the 250 yokes, I just assumed that they were aluminum the same as the KR and the 400.

I think it would be better to remove the clip, it is made of spring steel which may influence the weld quality. Once it is welded it won't do anything anyway so there is no real issue I would say.

Cheers

It is done

Thanks for all the help gang. In the end I gave up trying to grind the old stem out because I ran out of dremmel type discs & it was taking too long & I got bored

So using a stepped drill bit, a steel hole cutter (29mm) & a dirty great hammer, I set about speeding up the process.

Using the stepped bit, I opened the hole just enough so I could fit the hole cutter bit into it, this as you know stops the hole cutter spinning off the piece you're trying to work on, the stepped bit also helps to center the hole you are trying to cut.

After a good oooh, 3 minutes cutting, I gave the stem a bloody good whack with my hammer & the stem came free

Popped the new stem in & tapped gently into place but I think I will wait before welding it up as the Kr1 stem is quite a bit longer than the Zxr250 stem & I don't want it coming too far through.

Hope this all makes sense?

I used zxr400h forks and yokes and spaced them like the lc boys do when they fit rgv etc front ends you dont have to cut or weld anything although it might be too late by the sounds of it? If not links engineering do alloy lc spacers here is a pic i took at the time which makes it easier to understand what i mean, obviously you could put the spacer under the bottom bearing or whatever. I just popped it on top to take up the gap and put the top yoke on. Its still the same now 5 years on and no problems

Great photo John =D>

I may get my ZXR400 forks and yokes out of the loft and give it a go

Cheers,
Bernie