Race Tech Cylinder Seals

[JohnScott]

I put RT Gold Valves in my '00 YZ250 this weekend - learned a lot. Anyway, my kit included "Cylinder Seals" they discs the same diameter as the rebound cylinder and have o-rings on the inside and outside. What is it's function, does it help/hurt? They were a PIA to install and a bigger PIA to get back out (without tearing/stretching the outer o-ring) when I found I made a mistake I had to correct. I left the midvalve alone (did not convert to a check plate) and in retrospect I wished I had not installed these seals.

John

 

[marcusgunby]

They block of the Cylinder valve that sits at the top of the cartridge-these have been know to be stuck open and cause excessive bleed.RT try to make every fork like a 94 KX so they are easier to tune to RT specs.

 

[Jeremy Wilkey]

Originally posted by marcusgunby
They block of the Cylinder valve that sits at the top of the cartridge-these have been know to be stuck open and cause excessive bleed. RT tries to make every fork like a 94 KX so they are easier to tune to RT specs.

I'd venture more like 89......

The Cylinder Valve has been greatly conjectured over. I think the function is somewhat of a "blow-off" as the design of the valve creates rapid valve area growth. After the shims begin to deflect..

The early leaking CV's were somewhat confused with just "soft" CV's of the late 90's. An example is the 03 KX, it has a very soft CV and many think its leaking.. Well yes it is leaking, but it’s a designed leak.. However the softer the valve, the greater the oil flow, the more likely they can be corrupted with foreign matter.. So it’s a frog and serpent relationship.

According to Ross Maeda, the CV is a valve designed to purge air from the top of the cylinder under fork pressure. This makes the action more consistent, more like the patented Twin Chamber of Showa...


One last thing that is important to consider, the gas can escape with little resistance with a very small orifice, but when fluid tries to escape it is meet with far greater resistance, and that is the best part about the CV.. Interestingly Tuners that install Oil locks on the top of 32mm Cart. Forks have difficulties bleeding the fork, because of the large amounts of air that can be contained in its cavernous top.



The interesting part of the deal is that KYB states no official design protocol for the CV...


Best Regards,
Jer

 

[Jeff Howe]

I haven't had a problem bleeding them yet, but thats interesting. I'll see if I notice it on the next ones I do(which will probably be my own).

 

[marcusgunby]

Jer do you mean the 03 YZ?

 

[Jeremy Wilkey]

Marcus,
What are we talking about? The 98-03 YZ, the 03 KX's

BR,
Jer

 

[Jeff Howe]

and the 03 RM?

RT CV seal = harsness due to aditional stiction. Maybe they "break in" but I've never left them in long enough to find out, couldn't stand it.

 

[Jeremy Wilkey]

Yes Jeff for sure.. You need to leave the CV's in long enough to test them brother..

Jer

 

[JohnScott]

Jer/Shocknut,

Should I leave them in or take them out? I've ridden a little with the new RT valves and don't notice much of a difference from stock - except they seem to ride a little higher in the stroke and don't dive as much when I'm braking. I haven't had the opportunity to jump any to test their bottoming resistance. What would happen if I took the cylinder seals out? I noticed the kit they sell for the '03 YZ does not come with the cylinder seals.

John

 

[Jeff Howe]

They probably ride higher due to the stiction from the CV seals. Do this...bike off the stand, front pointed straight ahead, put your hand on the front fender right beneath the number plate and just lean on the fender, not push just lean. A good fork is going to move relatively easy, a sticky one...well if bad enough (like with the CV seals) you will really need to lean on it to get it to move. But this is one way you can tests your "stiction". Expect some, but with seals that are broken in you should be smooth.

Why would they take the CV seal out of the 03 kit? Hmmmmm....unless they have decided to drop it(thank God) because the CV is the same as last year and the year before.

And Jer, you got me wrong, I was saying I never rode with the RT CV seal because it made the forks so sticky. In they go, back on the bike, lean on the fender...Holy crap....Off the bike, out they come, in the trash can they went. So I never rode with them long enough to give them time to "break in". But I have since that time felt plenty of YZ setups by local RT guys that have used these POS seals and they were all sticky too. Why do these guys ride with their forks like that?? I have no idea.

I like the cones, i like the consistent performance of them. I'll try the bumpers again one day, but I can't imagine going back to be honest.

 

[Jeremy Wilkey]

WOA! I'm sorry guys, and Jeff, I can't belive the confusion I've created with even you.. I like the Cylinder Valve.. I think like you that the RT seal is crazy.. I'm saying try the CV not the RT CVS...

Cool..

BR,
Jer

 

[JohnScott]

I'll be taking them out then. What do you think their removal will do to my valving? How many stacks should I go harder/softer on the RT sheets? I didn't adjust for my leaving the mid valve alone either - did not convert to a check valve.

John

 

[marcusgunby]

Jer im totally confused :(
you wrote
An example is the 03 KX, it has a very soft CV and many think its leaking..

i cant see a cv in the 03 KX fork.Am i missing it?

 

[Jeff Howe]

Wait a minute Scott. How do your forks feel now? Make note of the stiction now compared to when you remove them...to see if you can feel the difference. I'd be interested in your opinion. BTW, I have the same bike as you. Love the motor too. don't want a new one.

 

[cp380sx]

Originally posted by scott2466
I'll be taking them out then. What do you think their removal will do to my valving? How many stacks should I go harder/softer on the RT sheets? I didn't adjust for my leaving the mid valve alone either - did not convert to a check valve.

John

John, if you deviate that much from the RT specs you will might find yourself in no man's land. I'd suggest you start with the full RT setup first, then test the stock mid valve, and then the CV. Making multiple modifications simultaneously usually results in poor performance.

 

[JohnScott]

Thanks guys - good advice 380. Since I started with the stock midvalve in place, I'll just remove the cylinder seals and see what happens. I'll let you guys know what happens. BTW, I did notice the stiction using Shocknut's method.

John

 

[Jeremy Wilkey]

Marcus,
Just like in the YZ's its hidden inside the crown..

BR,
Jer

 

[marcusgunby]

I wondered why it had all those 0.15 shims-cant beleive i missed it-trouble is ive seen very few YZ forks.