I would like your opinion on stock valving

I have tried a different route with my suspension on my 2011 kx450f this time. I wanted to see how good I could make it with just manipulating all the basic changes possible. (springs, oil, oil amount,oil weight, and clicker adjustments) I am much better now than stock but I am at the point I need to change shims or modify the current stack to see if I can get any better. My main issue is I need the forks to absorb more of the high speed chop. (braking bumps at 3rd or 4th gear)

The stock shim stack has many large shims against the piston. Do you think if I started by removing two or three of them would this help my problem without creating two many other problems?

I am not against sending it out to a qualified tech. I am just interested in doing the R & D myself for a change.

I weigh 155lbs. have .44 springs in the front and 4.9 in the rear. oil weight and amount in the front is 310cc and 5 weight. I also put in a lighter set of psi springs I don't remember the rating.

Also have you guys noticed the spring perches cracking on the 11's? Mine are cracked. (plastic, why?)

removing some of the big shims will help, but it will remove a lot of low speed and high speed damping, what you really want is less hs with similar low speed, assuming its good on other stuff? conventional thinking is just remove some of the smaller shims in the hs stack, this is actually wrong, its not much different from removing big shims, it just has a smaller effect, to get less hs and keep the same low speed, you often have to use 0.15mm shims in the low speed part

eg one 0.15mm shim= approx 2 0.11 shims

but it will give less hs speed than the 2 0.11 shims.

so you would need to remove some 0.11s and replace with the equivalent 0.15s, to do this correctly you need to use a shim program like restackor, other wise you are very much guessing and would be better off just pulling some shims as it will be just as close,

its a wordy reply but so many think they know what hs and low speed are in a stack and its mostly rubbish....all shims are low and high, its just sometimes they have more influence than we realise, thats why people do lots of revalves and go in circles.

to get less hs and keep the same low speed, you often have to use 0.15mm shims in the low speed part

does the restackor say this?

my dynos show the opposite

a tapered stack with 0.10 shims creates the most linear damping. everything else you do will add HS.

I did post up a Showa stack once with the least hs I could

I did post up a Showa stack once with the least hs I could

I looked for a while and it appears I could read for a week and not sure I would find it. Could you post a link to it or point to it?

Could you also give me in your opinion and recommendation in easy to follow terms what shims to add or remove to achieve less hs dampening and keep the low speed dampening close to as is?

Also just to make sure I am on the same page, high speed is square edge bumps like braking bumps and low speed is landing from a jump? Is flat landing (with no downside) considered low speed? Is a high angle jump face considered low speed? Can you guys give a generalization of what creates high shaft speeds as opposed to low shaft speeds on an mx track?


I cant give a easy recommendation on your stacks as it takes about 20 minutes using the program to get a stack i am happy with(ie all the same low speed and 10-15% less high speed)the program is very good value IMO and you should consider getting it and having a play, $50 or what ever now, and it will serve you for bike after bike.

you are correct on your high and low speed terms IMO, i would say a steep jump face is often high speed, flat landings are hard to say, more mid IMO.

you could try 300cc it will help a little.

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