kz2zx
Pro
Nobody in Particular
Posts: 1166
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posted August 09, 2005 09:04 PM
6R forks...
Man, I thought about doing one of my patented photoessays about the 6R's Showa fork. I might do it yet when I put valving in.
Replacing springs was quite the adventure, though.
I was armed with the RC-51 and CBR1000RR/600RR peoples' experience. It was wrong (or I misread it).
This fork, I think, is different in some respects, the same in some others.
The disassembly was pretty straightforward - loosen the top clamp,. Remove the circlip at the top of the damping rod/rebound adjuster. Unscrew the cap. Crank down the preload adjuster until you can get an open-end wrench in between the cap and the spacer, in between the three 'prongs' of the preload transfer bars. Loosen the whole cap assembly with the BIG 32mm box end and a 17mm open-end holding the damping rod. Remove the preload adjuster barrel/hex. Remove the cap. Now it's like any other damping rod fork - pull the spacer (two peices) and the spring, letting the oil run off in the fork.
The spacer length I used was 80mm, vice the OEM 109mm. My new springs were 22mm longer than the OEM ones, and I would ordinarily need 55mm of preload on the spring for my weight and the spring rate I chose for 20mm sag, if these were normal forks.
But they have this 'long top-out spring'. And you want, I think, and some others have hinted, the bike's free sag to be in the range where the topout spring is applying force. This way, the rider's weight moves the fork down UNDER the topout spring's range - and the topout spring will start to apply force (be compressed) just slightly - like 5mm or less - above the rider's sag when he's in a up-and-down-throttle-open position. [ In other words, as soon as the rider aggressively hits the throttle exiting a corner, the topout spring should be helping keep the front wheel down on the ground as the suspension extends 5mm past neutral riding position...]
So I cut the spacer at the length that would give me 5mm of compression on the forkspring to be free of the topout, at the rider's weight. This came out to 80mm... we'll see how it feels at the track this weekend. If it's really close, I'll post up the math I used to get there.
The spacer... I used 1" Schedule 40 PVC. I did not make a centering extension to guide the spring. I think it's possible the spring can rub the damping rod at the top of the spring, and after I ride the bike on the track one session, if I'm happy with the length of the spacer, I'll cut the OEM spacers and order new ones from Ron Ayers (and wait while they take the slow boat from Japan...).
Reassembly was pretty much the reverse of assembly, but I had to use safety wire in the groove for the wire clip and a helper with a pair of pliers to pull the damping rod up against the topout, so I could thread the cap on the damping rod. As long as you have the 32mm and some other basic hand tools, you should be able to do this at the track with a helper.
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ASMA 47
WERA 147
www.dhowellbooks.com
  
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extremelean
Pro
Posts: 1651
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posted August 09, 2005 09:21 PM
I have special tool.
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kz2zx
Pro
Nobody in Particular
Posts: 1166
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posted August 09, 2005 09:27 PM
Yeah, if I had four 1/8" cable smash-buttons and a turnbuckle, I'd have made a tool to compress the main springs. Does the tool pull the damping rod up against the topout? This part was what was puzzling me for how to do with the fork in the bike - if I'd needed even 1mm more preload spacing, I'd have needed some tool to do this.
____________
ASMA 47
WERA 147
www.dhowellbooks.com
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bovinespongiformencephalo
Pro
variant Kreutzfeldt-Jakob
Posts: 1060
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posted August 10, 2005 10:28 AM
That's NOT the kind of tool he was talking about.
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