Bottoming Cone Installation

[KTM-Lew]

A buddy has bought a spare set of forks for his WR450 that we are gonna do up. Sub-tanks/bottoming cones/valving. He is going to send the shock to John Curea since he is so close to us and John will be at the races. Doesn't have any real problem with the shock but complained of harsh fork bottoming.

I haven't seen the cones yet but have some questions. My concern is how or if you re-use the cylinder-valve?

Any info would be appreciated. :worship: :yeehaw:

 

[terry hay]

Lew
We use a cylinder valve replacement kit that overcomes the bottoming situation.
You could replace the bottom out cone with a dozen different bottom out cones and you will fail to solve the problem. The main issue with the Yamaha forks is not the bottom out cone itself but the fact that it hits the cone in the fork place. The cylinder valve allows the fork to fall through its stroke, gathering momentum and crashing through the bottom out region. To try and compensate for the cylinder valve Yamaha have made the base valve fairly stiff and supply a heavy fork spring to boot. Still limited success. A longer bottom out cone will simply reduce the effective travel of the fork and the problem of the valve will still remain. I am sending a replacement kit to Bruce Clapham which he will let every one know how it works.
Regards
Terry Hay

 

[KTM-Lew]

Terry

Thanks for the response. My buddy has been contacted by the manufactor of the cones on how to do this. They eliminate the CV also. Is your product a Race-Tech part or of your own design?

Thanks again!

 

[Jeff Howe]

Lew, what brand? The C Cycle versions are the shiznit in my opinion. I have loved mine since the day I put them in.

 

[KTM-Lew]

Shocknut...
They are made by Racing Suspension Products. I expect they are CCycle's supplier,also.


Apparently you have to be a dealer to purchase from them. He bought them from a dealer that was unaware that they are not supposed to sell "over-the-counter". Whooops!
I guess they don't want to reveal their "design" so it doesn't get copied. Makes sense to me.

 

[terry hay]

Lew
The product is our own design. We have had it since 2000. You simply unscrew the CV and replace it with our kit. It is an exact replica of the CV except it simply runs a shaft bushing instead of all the internals of the valve. It allows you to dramatically lighten the base valve giving you a plusher ride as well as greater bottoming resistance. The kit would be appr. $50-60 US.
Terry

 

[Jeff Howe]

Them's the good ones baby! He's gonna love them things. Totally smokes the bumpers in my opinion.

 

[KTM-Lew]

Terry

The cones are designed to eliminate the CV also. Sounds like a 2 in one deal.

Shocknut

These with the sub-tanks should be the real deal! Have you done any sub-tank work? He bought the TooTech tank but doesn't like the design, poor oil drain path and too small, so is making his own with a sperating wall between the sides. I have the Tech-Care tanks on the way (Ebay) so we will get to compare the difference between the flow-controls. (metered flow in both directions on tech-care or metered on inlet/free-flow outlet on tootech)

 

[Jeff Howe]

Terry, are you saying you replace the whole head with your product or is it just a RT seal type thingy with a bushing? I thought before you described it as a thing like the RT seal but it don't sound like that right now.

Lew, if and when I buy tanks I'm just going to buy Enzo's from Jer probably. I have not used them yet, but I think I'll get them and try them out this summer. I was never all that excited about subtanks but I want to try them out now.

 

[terry hay]

Our kit replaces the whole CV. It contains no seal and therefore eliminates a great deal of drag also. The new 04 forks have a hydraulic B/O cone that is simply pressed into the CV. You simply pop this out and press it in to the new part and you're away.

Shocknut
I'm not impressed with the CV seal as offered from RT for 2000 and onward forks that came with alloy rods. The simply excaserbate the stiction.
Terry

 

[Jeff Howe]

Yeah, that thing is a POS. Lots of guys out there suffering excess stiction and beating their hands to pulp in chatter bumps with that thing. I find it completely amazing that some guys can't feel that in their forks and continue to race with it.

I put them in my bike once to check them out and they were back out before I ever rode it. In the forks, back on the bike, pump forks, remove forks and take that godforsaken thing out!!. It was scary.

No way was I going to ride with it, let alone recommend it or sell it to a customer.

 

[KTM-Lew]

Good Info guys!

 

[bclapham]

here is another thread i remember from a while back. it seems that indeed, RT just had a seal kit but it wasnt up to par and it seems that Terry simplified things further by just doing away with the CV and putting in a whole new part

http://dirtrider.net/forums3/showthread.php?t=70377&page=1&pp=10&highlight=cylinder+valves

i am really looking forward to trying this setup out- as for comments about back dating this fork 10 years, well, ive tried updating them with numerous revalves and have not been happy, so hopefully i can make life more simple and get something that works for me. Life is full of complicated things, so i am really starting to get around to the idea of making things simple (trust me on this one)

as for the sub tanks, i wonder if they came about as an artifact of the problems with the CV forks, getting around the whole problem of running loads of oil to prevent bottoming and loosing the desired plush feeling in the small stuff.

 

[KTM-Lew]

Bruce I tend to agree with your last post. At some point you learn not to p*ss into the wind. This is my first time working on a set of these with the CV so I have lots to learn.

Im sure Jer won't agree, but that's what keeps things interesting.

 

[Jeremy Wilkey]

You guys ...I'm telling you.. Its a crutch????!!!.. Bruce for such a smart guy you have some strange ideas about the orgins of things..

I'll stay out of this one for now.. But I still saying you guys deal with technology buy not dealing with it.. Its simple it may make your suspension better, but does not mean that it is a solution by which you can judge progress on a gobal scale.. (Bumpers aside)

BR,
Jer

 

[bclapham]

ouch, that one is going to leave a mark Jeremy! :)

as for strange ideas, are you talking about the CV replacement or the subtanks?

 

[terry hay]

Jeremy
Bruce is at a point where he hates his YZ forks after several attempts to reach a level of acceptence. Using a number of different methods including your suggestion of adjusting the midvalve lift.
I have offered him these parts free of charge to allow him to draw his own conclusions.
How is this a crutch and how can this hurt? If he likes our setup, great. If he doesn't the only harm is mine. I would have thought you would appreciate at least the test aspect of this.
Terry

 

[KTM-Lew]

OK.......

I think what Jer is refering to as a crutch is removing the CV when you really need to build a CORRECT mid-valve. The CV should be a very small player in the overall damping equation. When people say the CV is "leaking" is that because the stock mid-valve is not controling the oil-flow properly, excluding debris/damage? I don't have an opinion on whether the CV is good or bad. It is obvious that the mid-valve MUST be more of a contributing factor to the damping than the CV. The CV's purpose is to help the cartridge bleed excess air created by cavitation.

On the cones.....I don't like the bumper deal......remember them from the mid eighties 4054 WP and they were rough on the wrists.

Jer loves sub-tanks but after you get the basics right!???

 

[terry hay]

Lew
While you have your cartridges out simply place them in a tub of old oil with the CV exposed and pump! They don't just leak. They gush. Reduce this excess emission and you may not even touch the bottom out again, let alone worry what it's made out of.
Terry

 

[KTM-Lew]

Well...I'm not grasping why we need to control what the oil does after it leaves the mid-valve on the compression stroke??? Once it passes the mid then it becomes rebound related. Rebound issues related to aerated oil aren't gonna cause it to hang down in the stroke. If anything this should cause rebound inconsistentcy.

Maybe this is about cartridge pressure? :clue:

I agree that having it hanging too low in the stroke would allow easier bottoming. :)

 

[terry hay]

Bingo!!
It is all about cartridge pressure. When pressure is applied to a fluid that pressure is equal and undiminished in all directions. Naturally that pressure will seek out the path of least resistance in order to escape the cartridge. The low pressure (escape) areas inside the YZ cartridge exsist in the following order. Compression adj. bleed, CV, Base valve. The midvalve creates resistance as it travels through its stroke but the pressure within the cartridge is being produced by the damper rod entering the system. If the midvalve is set up to create excess resistance (greater than the base valve) it will also be responsible for cavitation within the cartridge. So, after the flow capacity for the comp. adj. has been reached the next path for the oil to escape is through the CV. Now, since Yamaha have been using the CV they have nearly tripled the stiffness of the base valve from previous models which all the while promotes oil emission through the CV. The problem is the flow through this valve is too great. The port growth area is huge in comparison to the base valve and the shimstack is fairly light with quite an area available for deflection. Naturally on big hits the oil exhausts from the top of the cartridge and the fork can fall through its stroke and bottom out too easily. So, knowing this you can see why I don't care what bottom out system you use. The fault lies in the fact that your forks are getting to the bottom out system too easily in the first place. Ask anyone that rides the blue beasties and they will tell you that they feel harsh, yet bottom easily. In order for the CV to work effectively I would like to see it have a reduced flow capacity. This would control bottoming more effectively and allow you to run a lighter base valve.
Regards
Terry Hay

 

[russ17]

I use of a heavier weight fluid in YZ forks then most.( except maybe shocknut) The fork seem to have a better resistance to blow through the stroke. So in my mind the use of a heavier weight fluid could be helping this excessive bleed of the CV and create a more pressurized cartrige. I also find that I have a wider range of the LS bleed also.

Russ

 

[bclapham]

Just out of interest Terry, one would imagine there is quite some bleed off from the CV on the rebound stroke, does the rebound side of things require valving changes as well?

 

[KTM-Lew]

Yea....I started thinking about why the Twin-Chamber is supposed to be "better" and it relates to the ability to create consistant cartridge pressure. Less aeration. Consistant damping in both directions! :yeehaw: :clue:

I think I'm gonna catch on.....if I don't slip off, huh.... :laugh:

 

[Jeremy Wilkey]

Hey guys...

Bruce... I was talking about the subs.. They are not a band-aid...



Some more comments about bumpers verse hydro stops... Bumper work better in low speed botomings.. Oil locks better for big bottoms.. I guess its the old 6 to a 1/2 dozen.. I like the bumpers but understand the advanatge of oil locks.. I've allways thought a hybird with an elastomer on the top of the oil lock would work best of both...

As for the CV stuff.. Heres my point.. When you put a seal or a locked unit you destroy the intended design.. I seem to think that having a consistent properly working fork is better than a emulsion fork.. Maybe you'll like the emulsion better.. I've made suggestions, but I've not given you the answers so if your frustrated I understand.. Do what works for you..and be happy in that..

As for the global perspective.. Sealing the unit is ignorant.. Perhaps working on a better set-up would be the wise idea for the so called suspension perfessionals...

BR,
Jer