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Hi,

I have a yz450f '04 and I'd like to get some work done in my suspensions but I'm not willing to pay somewhere around 500$ CAN to feel any difference.

When I hit big doubles or tabletops the suspensions keep bottoming and that hurts...I suffer and the bike does too. Anyway, like I've said I would be looking first for some DIY stuff. Instead of shipping my forks and my shock away, I'd like to know if there would be any kit available somewhere that I could fit in and obtain what I'm looking for. I'm pretty sure there's a way to change the valves yourself without any special tools...

So except for kits, where could I get springs, valves, oil and other stuff that would help my landings and handling of course? I'm 5'10'' 170lbs and I ride intermediate.

Thanks for your help!

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I'm not sure exactly what you mean by "valves". The "valve" consists of the piston and shims, which function to regulate the flow of oil.

If you are looking for shims, any number of retailers can sell you those along with the springs and oil you mentioned.

If you're looking for different pistons, MX-Tech will sell them to you at $175 for each end. No shims, just the pistons. You'll have to do the set-up and testing yourself. They'll also sell you the shims.

The aftermarket companies that sell a valving kit typically have one consisting of pistons and shims, along with instructions.

I believe you will find that current KYB piston designs are quite good, requiring only shim changes to suit the rider.

The biggest problem I've seen with the forks is getting the mid-valve to communicate properly with the base valve to provide smooth, controlled action. It takes a lot of trial and error time on your own to get a feel for it, and then they still don't feel as good as the TC Showas, IMO.

Hope it helps.

😢

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Oh good infos, I tought that a valve was something like a restrictor that would slow the movement of the fork fluid. So I assume that a shim would be a sort of plate with different hole size depending on what you're looking for?

So what you're saying basically for me, I only need to change the shims in the KYB forks nothing else??

What about my springs rate? They're stock and I weight 170lbs, I think that's not enough? Am I right?

Thanks a lot.

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Click here to see what a piston looks like, and here to see the shims.

I'm saying you shouldn't have a need for an aftermarket piston, perhaps just some shim changes and maybe different springs.

In a shock you have shims stacked on the top and bottom of the piston. The bottom side controls compression damping and the top controls rebound damping. (The fork has a midvalve and tuning them can get real ugly! 😢 )

The fluid is directed through the ports in the piston and is forced against the shims, causing them to deflect to allow the fluid to flow by them.

By varying the thickness, diameter, order and number (along with some other variables) you can alter the characteristics of the shock action.

The "valve" consists of all these components which work to direct and regulate the flow of the suspension fluid.

Knowing what to do is the key and is a result of much experience. You will find many different approaches and theories on what works best, and probably very little agreement among the various parties. 😢

What you will get agreement on is that there is no one-size-fits-all solution for every rider that has the boxes on the info sheet filled out the same. Just because Rider A is a 165 lb, C class MXer on an 04 YZ250F, and so is Rider B, it doesn't mean that they are going to like, or need the same suspension set-up.

There are other variables such as preference for feel, riding style, etc., that cause variation in the final settings.

As for springs, using MX-Tech's calculator, they recommend using 0.43-0.44 kg/mm springs in the forks (stock is 0.46) and a 5.2 kg/mm shock spring (stock is 5.3) based on your specs. You'll also get some variation on these recommendations from different tuners based on their approach to set-up.

You'll need to get advice from the tuners as to what they have experienced with this bike, but it looks like the shock spring is very close to the recommended rate and the forks could be softened some.

I use my 03 YZ450 mostly for offroad and had to drop the spring rates from stock for my weight (165) because the suspension was transmitting too much feedback to my wrists which are more sensitive since they've been broken numerous times. It's noticeably better but the forks still need to be revalved to alleviate the harshness inherent in these KYB's. As you can see, personal needs factor into this set-up.

The biggest thing is knowing what shims and in what configuration you'll need to achieve what you're looking for. If you don't know or have an idea, it may be best to pay someone to do it for you. This can be cheaper (and safer) in the long run.

BTW, if you're experiencing bottoming in your forks, you can try increasing the oil level to firm them up in the latter part of the stroke. There should be a diagram of this effect in your YZ manual.

😢

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