KR1-S Cartridge Fork Conversion
Posted: Mon Jan 18, 2016 2:37 pm
I've just converted my KR1-S forks to cartrige type with rebound damping.
Unfortunately I forgot to take pictures, but the process is fairly simple, but I had all the parts lying around, so decided to give it a try. So here's how it goes.
(EDIT - Jus found this, has some pics viewtopic.php?f=11&t=12896)
I used VTR1000 chrome stanchions, caps & cartridges, which I had left over from another project. I also used VFR800 springs & valves to get better damping rates & fitted these to the VTR1000 compression rod to add rebound adjustment.
There are only 2 issues with this setup & that is the h***a cartridges use a M8 bolt to secure them to the base of the lower alloy slider & the KR1-S uses a larger steel bolt (M12 ?,I didn't measure it) that screws into the steel at the base of the damper rod. The second is that the h***a cartridges will NOT fit through the KR1-S stanchions, its close & they could be bored out but that is NOT reverable & the inner bottom of the KR1-S stanchion is deeper than the h***a's, so would lose wheel travel.
To get past the 2nd issue, just use h***a stanchions, I had these to hand, so no cost to me.
As an FYI the fork caps are interchangeable, I tried KR1-S. VTR1000 & VFR800 caps all fitted the chrome stanchions !
To deal with the 1st issue, I turned the KR1-S bolt threaded area down to 8mm, then cut an M8x1.25mm thread on it, this allows the KR1-S bolt to mate to the base of the h***a cartridge.
Both the KR1-S & VTR1000 springs are too soft for me, so I used a spare set of standard VFR800 springs & spacers I had lying around, these work out to be the perfect length to fit this hybrid fork, with KR1-S bottom & VTR1000 top stanchion. My thinking here, was that as the VFR is much heavier than the ZZR250 that I have the KR1-S frontend one, then they should be about right, they are around .75-.80Kg/mm compare to the VTR's .58Kg/mm (not sure what the KR1-S rate is as standard but soft to me).
The last modification was to grind the rebound damper taper on the VTR rebound rod, to be a full taper, rather than the limited stepped one they have as standard. You can read about it here http://www.vtr1000.org/phpBB3/viewtopic ... 31&t=29710
So cleaned & bolted it all together then added fork oil & set the air gap at 135mm & added the fork caps. Refitted the forks & front wheels etc & it all looks good. One advantage is the VTR stanchions are 54mm taller than the KR1-S so I can now mount my SV650 bars above the top yoke, which fixes the clearance issues I was having with the clocks & tank
I'm fitting a KR1-S swingarm to the ZZR at the mo, so can't report on the ride quality yet, but will do as soon as I have the bike back together.
Enjoy
Unfortunately I forgot to take pictures, but the process is fairly simple, but I had all the parts lying around, so decided to give it a try. So here's how it goes.
(EDIT - Jus found this, has some pics viewtopic.php?f=11&t=12896)
I used VTR1000 chrome stanchions, caps & cartridges, which I had left over from another project. I also used VFR800 springs & valves to get better damping rates & fitted these to the VTR1000 compression rod to add rebound adjustment.
There are only 2 issues with this setup & that is the h***a cartridges use a M8 bolt to secure them to the base of the lower alloy slider & the KR1-S uses a larger steel bolt (M12 ?,I didn't measure it) that screws into the steel at the base of the damper rod. The second is that the h***a cartridges will NOT fit through the KR1-S stanchions, its close & they could be bored out but that is NOT reverable & the inner bottom of the KR1-S stanchion is deeper than the h***a's, so would lose wheel travel.
To get past the 2nd issue, just use h***a stanchions, I had these to hand, so no cost to me.
As an FYI the fork caps are interchangeable, I tried KR1-S. VTR1000 & VFR800 caps all fitted the chrome stanchions !
To deal with the 1st issue, I turned the KR1-S bolt threaded area down to 8mm, then cut an M8x1.25mm thread on it, this allows the KR1-S bolt to mate to the base of the h***a cartridge.
Both the KR1-S & VTR1000 springs are too soft for me, so I used a spare set of standard VFR800 springs & spacers I had lying around, these work out to be the perfect length to fit this hybrid fork, with KR1-S bottom & VTR1000 top stanchion. My thinking here, was that as the VFR is much heavier than the ZZR250 that I have the KR1-S frontend one, then they should be about right, they are around .75-.80Kg/mm compare to the VTR's .58Kg/mm (not sure what the KR1-S rate is as standard but soft to me).
The last modification was to grind the rebound damper taper on the VTR rebound rod, to be a full taper, rather than the limited stepped one they have as standard. You can read about it here http://www.vtr1000.org/phpBB3/viewtopic ... 31&t=29710
So cleaned & bolted it all together then added fork oil & set the air gap at 135mm & added the fork caps. Refitted the forks & front wheels etc & it all looks good. One advantage is the VTR stanchions are 54mm taller than the KR1-S so I can now mount my SV650 bars above the top yoke, which fixes the clearance issues I was having with the clocks & tank
I'm fitting a KR1-S swingarm to the ZZR at the mo, so can't report on the ride quality yet, but will do as soon as I have the bike back together.
Enjoy