Too big of a rate change for clickers?

Hi guys, I wrote this in the KX450f forum as well but thought I should ask her, just in case.

I have an 07 kx450f and I just bought .49 for the fronts and a 5.8 for the rear. What are my chances of getting this supension to work as well as possible or have I passed in rate what the stock valving can manage?

Thanks.

the main problem will be your rear rebound.

Ok, I understand that even with stock spring the rebound is too quick. I guess putting a 5.8 on there isn't going to help matters. I'm not afraid to get in there and change stacks though. The local shop would charge up the nitro for me afterwards.

So after I remove the stacks I can list them here and people can give me their ideas on what would work? I am not confident enough to decide what should be done at this point in the learning curve.

Thanks.

sure people always help out if you are willing to put in the work, you have not done this but others come on here and just ask for everyones best hard earned stacks.

Well, I'm interested in a decent stack obviously... want my bike to work nicely, but I'm also very interested in learning about suspension and how the internals affect the characteristics of the bike.

I've messed with older KYB forks from 4 or so years ago but I think these 07's differ in many ways. I seem to remember reading that the compression stack is actually up top and not at the bottom like I am used to. If this is the case swapping shims would be so much easier. But, either way... I'm anxious to start trying new stacks and learning the differences in what shims cause what effect. I love this bike and want to get it to the point where it fits me really well. I know enough to realize that the stock stacks will not be adequate for the higher rate springs I am putting in there. I want to change the shock's stack as well but that's one thing I would rater not crack open time and time again... considering the nitro charging and all that. So ya... I would accept a stack from somebody who runs a 5.8 or so spring and rides local mx track... and is no Bubba Stewart. But I am definately game for messing with the fronts until I learn how they work and can get them to a point I like myself.

So... any pointers you can offer before I open them up?

Thanks again.

well what i tend to do as a first port of call is look at similar bikes, so lets say a 07 yzf 450 -the shocks are kyb and although the linkages rates wont be the same, i bet a good stack for one of the yzf would work decent in a kxf, by comparing the 2 stacks you can see the differences, i think some stacks have been posted before for the bikes-i have some std stacks at home if you cant find any, very few mind sharing std stacks, people get all upset as tuners wont give out there best stacks, but no tuners i know will do this, they cant all be horrible people? so we must conclude its not good manners to expect this.Again i am not jumping on you-you have done nothing wrong at all-we all enjoy helping people learn.

Hi guys, I wrote this in the KX450f forum as well but thought I should ask her, just in case.

I have an 07 kx450f and I just bought .49 for the fronts and a 5.8 for the rear. What are my chances of getting this supension to work as well as possible or have I passed in rate what the stock valving can manage?

Thanks.

A few things to add to what Mog has put in.

First, you cannot evaluate the performance of a factory set-up with the factory fluid in there. Doing so is like trying to tune a carburetor when the tank is filled with bad gas. Just doesn’t work.

Additionally, different oils behave in different ways so sometimes you can't make side-by-side comparisons unless you are really running the same stuff.

That said, if you have a particular problem that you're trying to solve, and you post the stack that you're running, we can direct you in which way to go in order to resolve the matter.

Lastly, nitrogen plays a big roll on rebound rates particularly when coming out of a full bottom. Consider this as well.

Ok... I guess I am getting ahead of myself. I will put in the new springs and spend some time on it first. I'm just not sure I will know 'exactly' what to report back about... I mean... the bike might feel fine to me but in reality it could be ten times better. I've only been riding for 4 summers now. I'm gonna try though and appreciate the guidance for sure.

Last year when I got the bike I was pretty sure on two things. First was that it really did feel harsh. I was waiting for the suspension to break in and it never really felt like it did. I surmised that at 235 lbs (me and gear) I was compressing the springs too far into the stroke making them harsh.

Secondly, there was a jump... nothing serious, maybe 20 ft., if I landed on both wheels at the same time I would bottom out enough to aggravate my ankles and wrists to the point I was left thinking about it afterwards. I learned that if I landed rear wheel first as to make the front do a slap down that it felt good and I could feel the front absorb nicely even though it was coming down much faster than when I landed both wheels at the same time. I guessed this to mean the stack was inadequate in mid-speed damping but fine for higher speed.

And also there is my concern that no one seems to like the rear shock on this bike. I read time and time again that it needs more rebound damping.

Did I come to the correct conclusion considering the symptoms?

Thanks.

P.S. Is factory fork oil that bad? If so what is their excuse for using it when the whole point is to have the best performing bike? Or does it work fine at first but deteriorate quickly?

well you are right about harshness, you maybe riding low in the stroke and riding in the stiff part of the linkage curve, and on the forks you will be riding on the airspring and that wont help.Landing both wheels down can feel harsh on all bikes,

std fork oil is horrible, it should be considered as break in fluid.

Ok... I guess I am getting ahead of myself. I will put in the new springs and spend some time on it first. I'm just not sure I will know 'exactly' what to report back about... I mean... the bike might feel fine to me but in reality it could be ten times better. I've only been riding for 4 summers now. I'm gonna try though and appreciate the guidance for sure.

Last year when I got the bike I was pretty sure on two things. First was that it really did feel harsh. I was waiting for the suspension to break in and it never really felt like it did. I surmised that at 235 lbs (me and gear) I was compressing the springs too far into the stroke making them harsh.

Secondly, there was a jump... nothing serious, maybe 20 ft., if I landed on both wheels at the same time I would bottom out enough to aggravate my ankles and wrists to the point I was left thinking about it afterwards. I learned that if I landed rear wheel first as to make the front do a slap down that it felt good and I could feel the front absorb nicely even though it was coming down much faster than when I landed both wheels at the same time. I guessed this to mean the stack was inadequate in mid-speed damping but fine for higher speed.

Okay…so here’s the deal.

I can’t say if you needed the stiffer springs or not since I did not see a reference to your weight.

In either case, based on what you have reported here, you’re clearly dealing with a suspension that is blowing through. This means that it takes a less than expected amount of energy to move the suspension through the stroke. This is also called over-stroking or over-oscillation. Stiffer springs will help, but springs do not manage velocities very well (or better put, converting kinetic energy into thermal energy) so you have to go back to the hydraulics.

P.S. Is factory fork oil that bad?

Yes.

If so what is their excuse for using it when the whole point is to have the best performing bike?

It’s a production break-in fluid and I think you’ll find that your manual recommends the replacement of the fork fluid after the bike has been broken in. It was never meant to represent anything other than that.

Or does it work fine at first but deteriorate quickly?

Most oils work best when they are new, then deteriorate at some rate. The better the oil, the better it holds up. Some fluids are so bad that they can be torn apart in a matter of 30 minutes or so. Once they break down, they don’t come back.

Do you have the means to service the suspension yourself?

Ok...

Last year when I got the bike I was pretty sure on two things. First was that it really did feel harsh. I was waiting for the suspension to break in and it never really felt like it did. I surmised that at 235 lbs (me and gear) I was compressing the springs too far into the stroke making them harsh.

Ummm? Dave? Read this post again...:thumbsup: :thumbsup:

Ummm? Dave? Read this post again...:thumbsup: :thumbsup:

I'm going blind. :confused:

235 it is.

I have an 06' kx450f, same shock different forks. I also weigh 235 so maybe you could benefit from my set up. On the shock I did as mog suggested and copied for the most part, the stack from a 07' yzf450 as this is a well suspended bike. I say "for the most part" because there are some changes. I believe on my low speed rebound I added 4 or 5 shims, i have it written down at the shop so i'll post the exact amount later. I changed the high speed rebound a little also but not as much. I also added at least 4 shims to the low speed compression, and the high speed compression is a lot like the stock yz 450. I can't comment on your forks because the valve stack is more like the yz sss so that might be a good place to look. Do a search there are stock stacks for your bike and the yz on here. Do like dave and mog said and change your oil when you change your springs, no choice on the forks. When you have your forks apart make sure the inner chamber is bled properly, the damper rod should extend all the way on its own. Read your manual it will coach you through the fork job. Last but not least, this site is such a valueable tool with so many excellant tuners such as dave and mog. I thought i knew a little before i started reading on here, but i learned more about suspension in the last year then in the 20 years before that. These guys are very helpful, just remember like mog said don't ask for a specific stack because that is their lively hood. I don't mind sharing because i only do my friends suspension. Other than that i just do rebuilds and such. Any way, pretty long winded huh?

I'm going blind. :thumbsup:

235 it is.

It would have been smarter for me to list my weight in the first post... I think that's where most people would go looking for it. :thumbsup:

Yes, I am 220 lbs after a shower and a haircut. I am actually loosing weight right now and should be 210 in a month when it's time to hit the track... that's the plan anyway. I am guessing it's safe to stay with the .49's and 5.8.

I ride local mx track that seems to get pretty chewed up, develops ruts and good breaking bumps... there's never really a place that is flat and smooth. I want sufficient damping for landings and hard hits but something that feels plush and controlled would be so nice. My buddy's CRF450 feels like it floats over things that make me grip my bars tighter. My bike is always busy underneath me and has never felt plush.

DaveJ, I have the ability to work on these forks. Got a loaded garage and plenty of courage. I'm mechanically inclined so I'm not at all afraid to open these things.

Moto867, I'd really appreciate that. I don't really like the idea of cracking the shock open time after time and paying to have it recharged. Going with something safe would make me much happier. The fronts I'll crack open a million times, though.

I just measured the sag with a buddy... it was compressing 130 - 135mm and I wasn't wearing my gear so maybe 140mm ?

So.. this weekend I will remove the suspension and disassemble a fork and the shock to photograph and catalog the stacks then post here. I'm guessing that at my weight with the new spring rates it is a given that the stacks need to be changed, right?

Alright, looking forward to learning everything I can from you guys and being guided along the way. I'm really excited by the thought of learning about suspension and making this bike handle better.

Thanks everyone.

ok... got the forks and shock out. I have not disasemled them yet but am just giving you guys a small update. I've decided to just send the shock out and have it done professionaly... this way I can avoid all the trouble of air bleeding and taking it to be recharged with nitorgen... perhaps more then once. Figured I save myself some big headaches and get it done.

But! I am still very interested in sorting the front end myself and learning stacks from them. So.. I will get the stock stuff layed out and come back with them.

I have ordered new tires... 756's I think they were... but the main point is they are both one size narrower. I ride a track that is mostly sand and sandy burms.. I have read a million times that this bike benefits from narrower tires in sand or loam. Plus... I never liked the way the front wanted to push out on me in corners.

Thanks

ok, I found these stock stack settings on this site. I have sent my shock off to get it done. I will add the .49's to the forks. So... for the spring rates what do people suggest I do to the stacks to compensate for my weight of 230(with gear) and added spring rate?

I am 38 intermediate mx track rider... probably at the slower end of the intermediate spectrum. The track is a cross between sand and dirt sorta... more sand and it develops braking bumps and has many burmed corners but also plenty of flat ones that develop ruts. The track is rarely smooth and flat anywhere.

Thanks everyone.. appreciate the guidance.

Stock Valving 07 KX450F

Compression BaseV/V6MM ID

Qty Size

18 32.1

1 30.1

1 28.1

1 26.1

1 24.1

1 22.1

1 20.1

1 18.1

1 17.1

1 16.1

1 15.1

1 14.25

1 Spacer 20X1.51.5

4 11.25

Rebound (Active)Shim Size 6 ID

Qty Size

5 20.1

1 13.1

1 18.1

1 16.1

1 14.1

1 12.1

2 11.25

MID VALVE C/V (Active)

Shim Size – 8mm Check valve Lift Ht: approx .25mm feeler gauge

Qty Size

1 18.1

3 20.1

1 18.1

1 16.1

1 14.1

3 12.2

2 17.3

1 16X1.62 spacer

Hey Guys,

18 32.12

1 30.12

1 28.12

1 26.12

1 24.12

1 22.12

1 20.12

1 19.12 * This was missing in the previous post.

1 18.12

1 17.12

1 16.12

1 15.12

1 14.25

1 Spacer 20X1.51.5

4 11.25

Thanks for the correction Jake Z...

So anyone have any suggestions on what I might change on these stacks for .49's?

Thanks

you should not have to mess with the stacks(compression) for a spring change unless they are a problem.For the rebound you may want to add a few face shims.

We've had some success uding this stac and reducing the oil volume by about 20cc. Obviously not a huge change, but it's definitely a little more compliant in the rough stuff. Anywhere else, I doubt you'll even notice a difference...

Qty Size

15 32.1 ( 18 to 15 )

1 30.1

1 29.1

1 28.1

1 26.1

1 24.1

1 22.1

1 20.1

1 18.1

1 17.1

1 16.1

1 14.25

1 15.1 ( moved the 15.1 here )

3 30.1 ( moved the 30.1 here )

1 Spacer 20X1.51.5

4 11.25

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