Fork Upgrade Musings

[Charles]

Ok, so I def want to upgrade to a more modern fork setup, partly for looks, partly for stopping power/performance.

I recently snagged a good deal on a set of 2004 GSX-R600 fork tubes. So here’s what I'm thinking. I’ve been researching triple trees and bearing and tube diameters and crap so I can see what’s compatible. Tell me what you think of this. I went to allballs.com and went to the fork conversion link. I know that that the XS400 shares the same bearings with the FZR400/600, so I put 1988 Yamaha FZR400 in the converter and got the bearing size and all compatible bikes (and if you scroll down, you’ll see that, indeed, the XS400 uses the same bearings as the FZR). So I’m now thinking, maybe I can get a set of triple trees from another bike that uses the same bearings as the XS400/FZR400/FZR600. Great…but it seems that’s those sizes apply to older bikes with traditional forks, not inverted…but wait…not so fast! The Honda CBR954RR uses the same bearings and is an inverted fork. So I check the specs on the CBR. That uses 50mm tubes just like the Gixxer tubes I bought. I can just slide the Gixxer tubes in the CBR trees and theoretically have them fit right into the neck of the XS. Yea? Yea?

Fork tube diameter reference: http://aztec8.com/id79.html

 

[drewpy]

sounds like a winner, or you could use a aprillia front end that fits right in!

 

[Shaun Chandler]

Hey if it's just a matter of bolting up different triples I say great. That would be good to know if it will work I'd like to do inverted forks on my next bike.

If that dosen't pan out you could go another route. Are the triples for the FZR400/600 steel on bottom like our xs? You could grind the weld off your old stem press it out and weld it in the the FZR triple. Might require either a sleeve or builing up the stem dia.

Shaun

 

[Charles]

Yeah. I've looked at the FZR triples, but I wanted inverted forks so I'd have to bore them out if I wanted inverted tubes to fit in there.
With the CBR triples, the tubes will already fit, and supposedly fit into the neck of the XS.
I'll pick some up soon and let you guys know what happens.

 

[Travis]

That would be awesome. Sometimes all that time researching online pays off. I think all you need to worry about now is stem length.

 

[Shaun Chandler]

Ya stem length would be a concern. I also wouldn't want to bore out the triples. They go slightly egg shaped just from use and being that they are split for bolting you would get a bad intermitent cut. That would make me nervous.

Shaun

 

[Charles]

Does anyone happen to have a stem from an XS lying around? Think you can measure the length for me?

 

[haga41cat]

sounds like a winner, or you could use a aprillia front end that fits right in!

Have a look at my old beasty i brought an Aprilia RS125 front end and it bolted straight on i just had to change the lower bearing to a 48x25x15

http://www.xs400.com/forum/showthread.php?t=5726

 

[Shaun Chandler]

Charles looks like about 8.930 inches overall length. Kinda hard to measure to precise being that its welded on one end. Thats from the top of the stem down to the bottom side of the triple clamp.

Shaun

 

[Charles]

Aprilia RS125s aren't sold here. I'm sure I could find parts, but not for cheap.

But for other people in the world...good suggestions.

 

[XSLeo]

Measuring from where the bearing sets to the top of the stem might be more meaningful.
Leo

 

[Charles]

Some more info I've gleaned while doing research

The fork tubes I have are from a 2004/2005 GSX-R600. They're 50mm diameter tubes.
The disc/rotor from the 04/05 Gixxer is 300mm in diameter. So it looks like FZR400/600 rotors will work, diameter wise (if you intend to use an XS/FZR front wheel, which I want to do). I've yet to confirm if the rotor needs an offset/spacer yet.
If you want to move up to 320mm rotors, there are spacers available that will move the caliper out to accept the larger diameter rotors.

The same year fork tubes will accept 2006/2007 calipers, but that generation uses a 310mm rotor, and I've yet to find a compatible 6 bolt 80mm bolt pattern 310mm disc (anyone know of any?). So if you want to use FZR rotors, you'd need to shave 5mm of the calipers where they bolt to the fork. For 320mm rotors, use a 5mm spacer.

Also, the Yamaha R1/R6 4 pot monoblock caliper mounts up to 2004-2007 Gixxer fork tubes. The R1/R6 uses a 310mm rotor (but is a different bolt pattern than the XS/FZR), so the same spacing/shaving would apply if you used a 320/300mm rotor, as if you were using an 06/07 Gixxer caliper.

Hope that helps anyone else looking to do a fork swap and can't figure out what fits on what.

 

[corruptmind]

I'm curious to hear if a CBR triple set was test. Till then I suppose ill look into myself.

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[Charles]

I'm waiting until I get all the parts. I have the tubes, triple trees (upper and lower), caliper, and clip ons. Soon, I'll be able to mock up and determine the disc spacer and axle situation. Hopefully I'll be able to do the whole conversion in the next month.

 

[corruptmind]

How's the stem length?

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[Charles]

haven't mocked it up yet, but here's a pic that might help

It's about 8.5" overall, beginning from the dust seal at the bottom. There are two threaded sections. The first starts right around 7" and the second starts around 8 1/16th"

 

[MotleyCustoms]

How did the final setup look/ ride?

 

[Jonesy]

Curious to see how this pans out, as I'm hoping to turn my XS into a cafe project and would love to improve the fork setup.

 

[Charles]

I'm still gathering parts.

I'm currently figuring out the options for the axle. I bought a stock GSX-R600 axle, so it will fit in the fork legs, but the stock spacers/bearings of the XS650 wheel (ebay seller sold me a 650 wheel instead of a 400 wheel, but I figure, it's not that much of a difference, so I'll use it) will be too small. I have to call up All Balls to see if there's a bearing that has the inner diam of the Gixxer axle, but an outer diam of the XS650 wheel bearing seat.

Still don't know if the stem from the 954 will be too long.

 

[Charles]

Another slight update. All Balls replied that they had a bearing with an OD of 52mm (the OD of the XS650 wheel bearing) and an ID of 25mm (the OD of the GSX-R600 axle), so, I'm a little excited that it might be somewhat easy to get the wheel on there. Hopefully, all I'll have to do is get some spacers lathed and I'll be set. From there, once it's mounted and centered, I'll figure out rotor spacings.

I'll keep this updated.