midvalve

[marcusgunby]

heres the pics bruce sent me-notice the feeler gauges to measure the lift-you need to remove the spring that pushes the shim stack closed so you can measure the lift easier-otherwise the spring pushes the shims against the feeler gauge and you get inaccurate readings.Its not possible to get very accurate readings on this.I go for 0.25mm increments.Once i set  a lift and decide to modify it i just add/subtract spacing shims and calc the new lift.It doesnt have to be exact as you just need to ride it and feel which way you want to go.

 

[marcusgunby]

this one, is off the peens after drilling-nice job BTW bruce.

 

[marcusgunby]

flynbryan IMO keeping the midvalve is the best option but i understand why people convert-its possible to get a good fork with a check plate-i really liked my 94KX125 and it used a check plate.I think its mainly down to tuners growing up with a check plate and feel more comfortable with it, or if they done the race tech seminars they are inclined to follow the same thinking.Its alot about who does the teaching.I learnt most of my stuff here and so i keep and embrace the midvalve.

 

[marcusgunby]

heres something interesting-the base valve i showed earlier had these shims-deltas-ive only seen these on KTMs rebound before the 1990 Cr500 forks shown in the pic.

 

[flynbryan]

Marcus is that the ICS spring in the 1st photo that you posted Marcus?

 

[flynbryan]

I agree that your probably right in your reasoning Marcus, I was told by this tuner that the midvalve design better benefits agressive rider so that w/ how the midvalve works if you dont' push the forks far enough through their travel you will experience a spike in the midstroke. With the checkvalve adjustment its supposed to help take away the spike, and since I run Harescrambles I am probably not very "aggresive". Just the tuners opinion and we know about opinions, but I've talked to several of my riding partners and they praise his mods.......so well see what happens:)

 

[marcusgunby]

Thats the top out spring.It stops the forks slamming to a stop when they rebound.On JTTs pic you can see the ICS.

 

[bclapham]

Originally posted by marcusgunby
you need to remove the spring that pushes the shim stack closed so you can measure the lift easier-otherwise the spring pushes the shims against the feeler gauge and you get inaccurate readings.

i took this measurement with the little spring still on, that said, the feeler guage was wedged in quite tight and i had the feeling if i put any more baldes in, it would have deflected the shims and given another false reading.

i will recheck again without the spring.
BTW, this fork is a stock 01yz426, anyone know what the stock lift is, i got 1.75mm, it would be nice to see how my reading compare to someone's that knows what they are doing!:)

cheers

BC

 

[marcusgunby]

ancient mystic guru voice on 'bruce you are but a child who i will mould':)

 

[steve125]

Marcus: I must warn you that is illegal here in the States! :)

 

[KTM-Lew]

I measure on the other side of the "stop-plate" instead, where the spring is located. That's what I call float---mid-valve acts as check-plate until stop-plate contacts rebound tap. The lift is determined by how much the stack floats plus the deflection. Not someting you can actually measure?

Am I doing this wrong or are we talking about the same thing? Remember I'm doing WP 43mm.

 

[bclapham]

Lew, i would say it doesnt matter, since if you do it the same everytime then your measurements are all relative....then again what do i know. The problem i see with suspension work is that it is alll clandestine operations, so its difficult to compare what you are doing with everyone else, more of a black art rather than a pure science!:) so unless someone writes a book on the subject (someone chime in and tell me there is one) who knows what is going on. I am sure a monthly journal such as Journal of the American Suspension Society or The Royal Suspension Society periodical would make a great read!hehe.

 

[marcusgunby]

KTM lew- its the same the way you do it.However on your stacks it easier to do your way as you have almost a check plate.A KYB stack is very tapered and its harder to do your way.

 

Bruce makes a very valid point-i do things my way and cant always convey exactly what i mean or how im doing stuff-so its not easy for someone to  reproduce my stuff.eg setting a air gap-i fill to the brim ,let stand and then remove some oil.Others pull the outer tube up and evacuate the chamber between the tubes and then set the level-gives very different readings.

 

[russ17]

MARCUS ! I have been doing some thinkining on the oil levels.I know we talked about this on another thread about some taking in concideration of the outer tubes being filled and others dont .but if you think about it when your using your travel oil does make its way to the outer tubes

 

[marcusgunby]

Ive been asked to put up these pics(by the owner of the forks) to show what not to do when drilling the peens.

 

[marcusgunby]

heres the scary one

 

[marcusgunby]

Russ i adgree the oil does enter the chamber as this lubricates the bush area.However as long as people state the level and the method its ok either way.I like to overfill then remove as this is inline with the published specs(i hope)

 

[russ17]

I know a tuner that does that, he doesn't drill into the cv but after taking the cv out he drills the hole all the way through.

 

[marcusgunby]

Tell me more-he removes the cv?what stops the oil blowing through the gap?and why then drill all the way through?

 

[russ17]

Yea he drills the peens, takes out the cv dills the rest of the peens the rest of the way, converts the mid to a checkplate( every time I saw him) puts the cv back in. I believe, no I know he said he drilled them all the way through was to clean the inside of the cartridge because of the point of the drill bit. The gap you are refering to is between the cartridge wall and the threads on the cv right!

 

[russ17]

Scary one! don't you like those 2-piece mid pistons or am i missing something

 

[Jeremy Wilkey]

Float is the measurment of the shims lift before they defelct. Thats the point float determines the area of the valve before the shims start to control area rate of change..

Removeing the midvalve.. MX,Offroad, Road Race. In any case, it ruins fork action. Period... You can only make a soft fork without a midvalve. If you atempt to build all your damping with one valve, and it has enough low to mid speed then it will contribute to much high..

So remove your midvalve only if you want a pillow that may feel smoth for a single bump, but will kill your energy over a series of bumps..


Marcus,
Is your suspension business starting to see serivce work with my products now? Or did you purchase that thing? One way or the other hold on to your hat, as something much cooler lies around the corner..

BR,
Jer

Russ,
The 2 part piston Rocks! Thats a great design for a active psiton. The two peices just make machining posible!

BR,
Jer

 

[flynbryan]

:eek: :eek: Jeremy so with that mod is it causing so much high speed damping that the fork will only deflect? Or is it packing? I'm a little confused on this. If this is such a bad idea why is it such a common mod?

 

[flynbryan]

Sorry Jer I was a little confused I thought you were speaking on changing the midvalve to a check valve system............or are you :think:

 

[Jeremy Wilkey]

Flynbryan,
The problem is "most" suspension tuners think they know something about suspension. Most are idiots, hacks and wanabees.. That’s just the reality of the suspension industry.. We are dealing with something very nebulus.

I also want to add one more thing.. I've meet lots of tuners who you won't hear about for some time but if they stick to it you will.. Size does not matter in suspension.. I know big guys who suck, and big guys who are very good. I no little guys who can do it right and little guys who can't.. ITs a grab bag.. But if they tout removing midvalves, they don't know what they are doing..

I'm not going any farther than that with the above statement but that is the ugly part of our topic. It dosnt take much more than a few of the wrong tools and you’re in business.. MX-TECH started on a $500 credit card 12 years ago.. Fortunately I managed somehow to overcome my hack origins.. But when people complain about spending a few thousand dollars on a special tool what’s that tell you.. Next time you go see the dentists and she pulls out a hammer, chisel and wipes the syringe off with an old rag consider the analogy.

I doing everything I can to elevate the consciousness of the consumer and the average suspension tuner but it takes time.

As for your questions here is the deal. Each aspect of the damping contributes to the overall.

Basevalve+Midvalve+CV= Overall damping coefficient.

If we have some minimum level of damping requirement.. (We all do although the exact amount is arbitrary.) If we only use one of the valves by the time it produces enough damping in the low speed range it won't have enough mid-speed to control bottoming. If we stiffen it further then it will also produce too much high speed. When we divide the different components up then each one contributes to the overall, but its overall contribution can be focused. That reduces compromise.. So when you go base only, you’re harsh, or soft.. That’s your choice.

Is that explanation any better?

BR,
Jer