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Wernersville, PA
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Edited Date/Time
4/13/2020 3:08pm
Getting ready to install Race Tech Gold valves in my 88 CR250, though I post some photos of them disassemble showing their simplicity and ease of cleaning,
Photo show damping rods removed, very easily done by removing cap, pulling out springs, removing lower leg compression dampening bolt.
Dampening assemble pulls right out, after draining oil of course.
With the dampening rod laying on the work bench, I remove the retaining ring usually this is finger tight, if not a light tap with a punch loosens them, I then install the comp. bolt back in and pull out the base valving, lower right.
Last photo show rebound dampening rod with return orifice and stack.
I was glad to see how clean these parts are for an all but 30 year old bike comp. bolts are almost like new.
Picking up the kit tonight will try to get some pic's of valving change over
Photo show damping rods removed, very easily done by removing cap, pulling out springs, removing lower leg compression dampening bolt.
Dampening assemble pulls right out, after draining oil of course.
With the dampening rod laying on the work bench, I remove the retaining ring usually this is finger tight, if not a light tap with a punch loosens them, I then install the comp. bolt back in and pull out the base valving, lower right.
Last photo show rebound dampening rod with return orifice and stack.
I was glad to see how clean these parts are for an all but 30 year old bike comp. bolts are almost like new.
Picking up the kit tonight will try to get some pic's of valving change over
Next is measuring all the race tech shims and get ready to build my specific dampening.
Looking at the stock pistons the design isn't to far from the modern open chamber forks. Could use a smaller rod to decrease the work load at the basevalve but otherwise pretty 2016 looking.
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On comp. there's a small valve stack and rebound it has orifices controlling oil flow, percentage of overall effect not sure. the cartridge body also has orifice to help the hydraulics of this fork.
Next time u do an oil change and bleed the cartridge you will feel this as you bleed the air out, then the oil flowing through the piston creates a resistance.
Trick stuff
I'm well versed on current open chamber forks and close chamber forks designs for the last 30 years which all use shims to dampen during rebound rather than the old school orifice holes.
The basevalve works by choking the oil displaced by the rod during compression. The midvalve works by restricting the oil flowing around the valve during compression. It flows more oil than the basevalve and is more speed sensitive because of it. Racetech usually disables the midvalve so that the basevalve does all the work which makes it easier to tune but decreases the overall range of the fork. For most riders that is fine especially ones that aren't going to do a lot of testing.
Good stuff and thanks for sharing. I have a set of 87 and 2008 43mm conventional forks waiting for my attention this winter.
Ya know the more I though about it, the harshness everybody complains about these fork is probably due to the mid valve.
I know they modify this on the Suzuki twin chambers due to distorting, I'm going to look, I think I have a set of 86/87 fork and see if there is a difference in mid valve stacks. Thanks for the tip
The way I see it, rebound is controlled by shimstack on "midvalve", but to adjust rebound you change spring preload and/or oil viscocity, or change the shimstack.
Compression is controlled by basevalve, checkvalve on midvalve open on compression.
I tried to visualise what I mean, english is my second language and pictures are universal..
I stolen your pictures wolfy, hope you don't mind.
Please comment or correct me if I have misunderstood something.
I'm not a fan of adjusting rebound with oil viscosity or preload so I'm a little surprised racetech recommends it. Preload should be for ride height and oil for fine tuning of compression and rebound as it affects both.
I should clarify what Race Tech told me: THEY do not make a Gold Valve for the midvalve/rebound damping.
This is why they say adjust the rebound with oil viscocity. Yes it will obviously affect compression too - in my thinking I'll try to get the compression in the ballpark with the clicker (comp adj), then see where I'm at with rebound. If it's too much or too little, replace oil with higher or lower viscocity as needed, finally dial in final compression after that.
I haven't really looked at my midvalve setup. You probably could take it apart and revalve it. It would be a pain to take the forks all apart every time though. Seems easier to just alter the oil visc.
The midvalve circuit is a tricky one to nail so most of the time having a none working midvalve circuit works for most. That said when you get it right the control of the bike is awesome and you feel like you can attack the corners and whoops.
I also check my 87 forks and the cables are a lot different, sticking with the 88 internals for now.
preload
I get a little confused when there is talk about midvalve and compression damping, but of course everything works together and affects each other.
It sounded a little backwards with adjusting rebound with preload, sound much better to choose springs for weight/riding style, preload for ridehight/sag and viscocity for damping.
It would be easyer if there was adjustable rebound, I find it hard sometimes to know if I want more or less damping and its so easy to try with clickers..
Most of my riding and testing suspension is on enduro trails, and I know that setup doesn't work on mx-tracks with big jumps.
What do you think of Race Techs spring-rate lists? they recommend 0.47-0.485 kg depending on varibles..
Race tech or Eibach springs?
I am 100-104kg +gear, slow/medium rider, 188cm tall.
The bike is CR480 -83 with -88 CR250 forklegs.
I was thinking to start with Bel Ray 15W oil.
Pit Row
Wanted 48 due to this chassis being raised in the back and steep rake, want to keep the fork higher in the strike I. An effort to elimate head shake, my 87 cr worked great with this setup. I installed this dampening setup in my 83 cr with much success.
I couldn't even start to use the stock 83 forks.
Hope this post helped anyone who has never did a fork disassembly, cleaning or revalve.
And thanks for everyone input.
I find this topic very interesting. Although all this is still confusing to me. I have this fork and I'd like to understand something.
Does the oil trapped in the tube between part 1 and part 2 circulate only through the valves (green lines) or can it also easily pass through the outside of part 1 (red line)? Because on my fork, there is a lot of play between the tube and the part 1. The oil could pass on the outside (the red lines) quite freely.
On the new forks, the inner cartridge is filled up with oil first, then the fork is filled. That's not the case on this fork ? I know all of that are beginner's questions....
Yes, well, that's what I was worried about.
Honda doesn't sell the piston band. You need to get the assembly piston. Changing cartridges + pistons is about 300 € x2.
So I will build it like that for now, and see how does it feel.
I have what I believe are Showa cartridge forks of an '87 CR 250 that I acquired with a bunch of other bits from ebay. The only markings I can find on them are a very worn Showa sticker and 'KA4-RHK-1 S' stamped on the right leg and 'KA4-LHK-1 S' on the left leg. I've just stripped them down and it looks like I either have a bunch of parts missing, when compared to this diagram, the rod piston being the most obvious, or I've got a different set of forks to what I was told.
The components I have were assembled differently in each fork leg, so clearly whoever was in there before me has just thrown them back together and walked away whistling nervously..
Appreciate it someone could confirm, or otherwise, what forks these are and point me to any resources that will help me (parts catalog, rebuild guide, source of missing components).
I got these forks, along with the triple clamps to upgrade the originals on my '79 Cr250 that I'm currently rebuilding.
Many thanks.
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