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Fork shim stacks for 05 CRF450
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Posted by: Yoken---------------------

Hi fellow enthusiasts,

Could someone post the detailed stock shim stacks for the fork of the 05 CRF450 ?

- Base valve comp and reb stacks,
- Mid-valve float, comp and reb stacks.

Although the bike handles well in stock form, it bottoms out pretty easily on big jumps and charging through breaking bumps on lap 5 makes me feel really old (...maybe I am?).

I'm just curious to try a couple different shim stacks on my own and see how it goes. I'll give myself 2 to 3 trials. If it fails, I'll ship the forks to a professional tuner.

Thanks,
Yoken

Posted by: kawamaha---------------------

i have just the:
base valve compression

http://www.*********************/e/

Posted by: Yoken---------------------

Kawamaha,
I had a look at your link and like the idea of re-drilling the clutch perch for an easier pull. I heard about it but never saw a sketch. Thanks for sharing that with us. Although the Honda clutch is pretty good, I'll give it a try. I finally took the fork apart. Here are the specs I found :

BASE VALVE (id=6mm)
(from the bottom to the nut)
At this point I already have a question. The base of the stem is shaped like a cup and is drilled with 6 small holes. Those holes communicate with the exhaust ports of the needle circuit (LSC clickers). That "cup" is topped with what looks like a small/stiff valve stack
10 x 16.1
15.1
14.1
13.1
12.1
11.1
16.2
I can't figure out what it does. Any ideas?
The above stack is then followed by a stiff "base plate"
6x30.5x2mm
then a more standard (rather thick) single stage stack
18.1
19.1
20.1
21.1
22.1
23.1
24.1
25.1
26.1
27.1
28.1
29.1
16x30.1
PISTON
check plate 8.1x30.5x4.5mm
spring
cup washer
nut.

MID-VALVE FLOAT
Because of the fairly soft shim stack, it was quite difficult to measure it accurately with a feeler gauge. So I calculated it by measuring the thickness of the different components and found : 0.25mm (which feels about right with the feeler gauges)

MID-VALVE STACKS
(from the bottom to the nut)
Cup washer and spring
id6xod10x0.2mm spacer
id6xod10x0.2mm spacer
id6xod5x0.2mm spacer
id6xod8x2.25mm collar (on which the shim stack "floats")
COMPRESSION STACK (id=8mm)
4x17.1
6x20.1
PISTON
REBOUND STACK (id=6mm)
20.1
20.1
18.1
12.1 cross-over
16.1
15.1
14.1
13.1
12.1
11.2
3x16.3 spacers
washer 17x2.5mm
nut.

That reminds me a bit the WP setup of my old '02 KTM520. I think that the mid-valve float is a bit too large and causes the damping to come into play too late and/or at too high speed. To compensate, the base valve compression stack seems to be build quite stiff. This, added to a high oil level, is probably why the fork feels so stiff in breaking bumps.

So basically, I am thinking to :
- reduce the mid-valve float (0.15mm?),
- change the mid-valve compression stack to something more like
20.1
19.1
18.1 ...
- lighten the base valve compression damping. Something like
4x30.1
29.1
28.1 ...
- reduce oil level.

What do you think ?
Yoken

Posted by: marcusgunby---------------------

I wouldnt say 0.2mm is alot of float, if you add one shim it will be as small as 0.1mm??

Posted by: KTM-Lew---------------------

Quote:

MID-VALVE STACKS
(from the bottom to the nut)
Cup washer and spring
id6xod10x0.2mm spacer
id6xod10x0.2mm spacer
id6xod5x0.2mm spacer
id6xod8x2.25mm collar (on which the shim stack "floats")
COMPRESSION STACK (id=8mm)
4x17.1
6x20.1
PISTON

What does the "check-spring" push against & what is the ID & OD of the spring? The Twin-Chambers I've had apart didn't have a "check-spring" to close the floating shims but they were earlier models?

I'm assuming it pushes against the 17x.10?

Posted by: russ17---------------------

I'm assuming it pushes against the 17x.10?[/QUOTE]

You are correct!!!!!

Posted by: KTM-Lew---------------------

So have they lengthened the tap to allow room for the cup? Hmmmm? I guess since they always had those long post spacers there was enough room? Vedddyyy int er esting

Posted by: russ17---------------------

The showas doesn't have the cup like the KYB it's more like a base plate that has a groove in it. the spring rest in the groove on the base and pushes against the 17.1. In order to change the float you need to either add or subtract shims. or change the height of the collar. Of coarse this is dependent on the build and the amount of float you desire.

Posted by: KTM-Lew---------------------

Thanks Russ!

Posted by: Yoken---------------------

Marcus,
You're right, 0.25mm float is not too large. I went back to my notes and the float on my old KTM was around 1.25mm... (I should've read my notes before posting. Sorry).
However, I've see floats of about 0.1 to 0.15mm working fairly well with MV shim stacks like 20.1 - 19.1 - 18.1 - 16.1 - 14.1 - 12.1 - 10.1. My problem is that I don't know what base valve was associated with it. I'll have to make my own experience.
How would you compare the above stack versus the stock 6x20.1 - 4x17.1 ? Stiffer or softer ?

KTM-Lew,
I'll try to get you a pic of the MV as soon as I figure out how to link it to this site. Russ17 made a good description though. For info, the spring is ID13.5xOD14.5mm. It sits in the groove and pushes on the 17.1.

My goal is to get :
- more plushness in braking bumps,
- a bit more fork dive at the entrance of a corner (spring rate? preload? bleed circuit valving?),
- while maintaining stock bottoming resistance (getting a bit more would even be better)

...am going to think about it a bit more before I start messing things up.
Yoken

Posted by: russ17---------------------

Quote:

Originally Posted by Yoken

Hi fellow enthusiasts,

Although the bike handles well in stock form, it bottoms out pretty easily on big jumps and charging through breaking bumps on lap 5 makes me feel really old (...maybe I am?).

Thanks,
Yoken

your weight and ability could be helpful.

Posted by: Yoken---------------------

5ft11 (1m80) - 205lbs (93kg) with gear - Turning 36 next week.
B rider when the gate drops... C after 3 laps... and S (Soar) the next day... that fork is killing me!

Rear sag was set at 100mm. I haven't checked the front end though but the bike felt well balanced in stock form. Fork oil level was stock too (but not measured). The bike felt great the first time I took it out. It was on a smooth hardpacked amateur supercross-type track. Then my joy disappeared when I hit a fast MX track...

The stock springs should be about right for me. However, somebody mentioned that the fork spring pre-load was a bit on the high side and that he had positive results when backing it off 3 to 5mm. I'd like to check that out. I've always liked to have "stiff" springs with low pre-load on my previous bikes.
Thanks for your input,
Yoken

Posted by: marcusgunby---------------------

Yoken i would never go on this board and try to claim to know which stack is stiffer or softer, once you alter the float its very hard to compare, ive seen a few showa mid valves, and the ones on my 04 rm125 wanst nice with a stiff stack and more float(0.2mm i think) IMO a softer stack with less float(must be 0.1mm to be easily changed) works nicer.

I will admit i have not changed the mids much on the showas, i do know many claim it needs doing, but they are not a bad fork with just a base valve shim change.

Posted by: Yoken---------------------

KTM-Lew,
As promised, here is a pic of the MV base plate (1st trial. I've never made any attachments before...)

Posted by: KTM-Lew---------------------

Thanks, looks like a very light spring. That is what I was wondering about!

Posted by: Yoken---------------------

Marcus,
I agree with you. The stock Showa is not a bad fork at all. It's in fact the best I've tried so far. The Kayaba of my old 99KX250 and the WP of the 02KTM520SX were far worst in stock form, IMO. However, by just softening the BV I'm afraid to have bottoming issues. I'm not a talented rider and I do land heavily quite often...

I've just checked the fork spring pre-load : 6mm! That doesn't seem excessive too me. I could back it off 3mm, but I don't think it is going to help much in breaking bumps though.

Please see attached pics. Is this what you've called in earlier posts "a shim stack on the bleed circuit" ?
I really don't understand how this works. How could the oil have enough pressure behind the needle to flow through those 6 ports and deflect the shim stack? The 2 exhaust ports of the needle circuit should be more restrictive for that to happen.
Plus, what's the point of having a shim stack in series behind a needle?... I feel a bit stupid to ask, but that thing has been driving me nuts for two days!

Posted by: kawamaha---------------------

this is for the compression adjuster. first it's a check valve so it does not influence the rebound damping when you change the compression clickers. you ask "How could the oil have enough pressure behind the needle to flow through those 6 ports and deflect the shim stack". Of course it has enough pressure. it is only a small amount of oil (the needle is just for low speed compression) so the shims need to open very little.
but for me it is more a gimmick than a serious thing

Posted by: russ17---------------------

try a set of .49 k/g first and start eliminating some of the 16.1's from the bleed stack. Then play with the base. This will give you a better idea of what the changes will feel like.

Russ

Posted by: marcusgunby---------------------

Yoken you really have 2 extremes of forks listed, the 99kx250 has a mid valve with no real lift and plenty of damping, the ktm is the opposite, it has alot of mid life and no real shim stack strenght, yet you notice both are bad forks, so this tells us we need the correct amount of damping, too little or much is bad, the advice given by russ etc will really help, i used to think every fork needed major work to get it perfect for me, then after about 5 tries on the kxf it was a stack very close to std that was the best.

Posted by: steve125---------------------

I hate passive bleed shims!!

Posted by: bclapham---------------------

i would tune with just the base valve on that fork. a big bike like a 450, if you take out too many shims its gonna ride too low and feel worse. Plus, its more likely gonna bite ya.

Posted by: Yoken---------------------

Thanks for your input guys!

Kawamaha, "gimmick" is exactly what I had in mind but I just didn't dare to mention it... I'd be curious to see how a bleed stack shows on a dyno though, if it does.

Russ17, you are the 2nd person to tell me to go stiffer on the springs. Interesting and quite confusing. I am not sure if I am fast/aggressive enough to use stiffer fork springs. With current springs, the bike won't turn unless I stay on the front break and sit on the gas cap! So I'm afraid to go stiffer at this stage. But I'll follow your (and Marcus') advise and will start by softening the BV stack and move from there.

For info, I put the fork back together on Friday and went riding yesterday. You can check a couple pics of the track at www.jbmotocross.com. That will give you an idea. Unfortunately, it was not a high speed MX track so I could not test the breaking bump issues... but here is what I tested :

FORK
Fork height: base of the fork cap 7mm above clamps
cartridge oil: Bel-Ray 5W
Valving: Unchanged (stock)
Spring pre-load: reduced from 6 to 3mm
Oil volume: 350cc ATF (stock std setting is around 382cc)
LSR 6 out
LSC 10 out
Dunlop 742F @12PSI

SHOCK
LSR 8 out
LSC 10 out
HSC full out
SAG 100mm
The rest (oil, N2pressure, valving,...) is stock
Dunlop 756 @12PSI

The bike handled pretty well. I had less vibration in the bars on small accelerating bumps (locals call those hardpacked bumps "riding over a wash-board"...). The fork didn't feel like diving more than before under hard braking (I guess because of the stiff BV stack). I still had to sit on the gas cap to turn but the front tire felt more planted throughout the turn.

Front and rear bottomed out a couple times when over-jumping the tables or hitting the face of a jump too fast and off the gas, but surprisingly it wasn't a bone-breaking experience...

So now I'm going to order some shims and will get back to you guys with some more test results... tuning is just as fun as riding!

Posted by: Yoken---------------------

Bclapham... I'm afraid I've been bitten already. Went down 6 times in 2 months! Fortunately with only bruises and scratches... you see I can land on my head even without messing up with suspension settings! Thanks for your concern though. I'll definitely go step by step and won't charge to the 1st turn before I get a good feel of what's going on.

Posted by: bclapham---------------------

the important thing we found for cornering was the rear spring. with a 200lbs pro on board, the rear would squat comming out of corners on hard accel, even tho the spring has the right sag numbers. we went to the next spring up and it was better- made the rear end a bit higher.

Posted by: marcusgunby---------------------

I too have found a 4 stroke will just not work well with a soft shock spring, it ruins turning and balance, i can go down a little on the forks spring rate.

How did you reduce preload on the springs, maybe it sounds like a little less(maybe 1mm preload) will work for you, you could also expriment with different ics springs-however with so many variables its easy to get confused.

Posted by: Yoken---------------------

Interesting remark! Although I don't carry the speed and rage of a pro rider - not even close - I do feel in some turns that the rear end rides pretty low. As long as I keep my body way up front I'm fine. However, when I get tired and my butt moves back an inch or two on the seat (it doesn't take much really) then the rear end sags and I can no longer hold a tight line in the turns. I put that on the account of the stiff BV stack and high oil level. I never thought about going stiffer on the rear spring... I'll see how it feels after I soften the BV.

Marcus, to reduce the preload I backed off the rebound clicker ass'y 3mm on the damping rod. In stock form, the clicker ass'y was threaded all the way onto the rod and that's in that position that I measured 6mm preload. The clicker ass'y is not threaded all the way to the bottom so I figured I could back it off 3mm and still keep about the same thread surface in contact with the rod. Also, I made sure that the small "D"-shape rod (that connects the adjusting screw to the needle inside the damping rod) would not disengage with clickers full in or full out.

Posted by: russ17---------------------

Quote:

Originally Posted by Yoken

Interesting remark! Although I don't carry the speed and rage of a pro rider - not even close - I do feel in some turns that the rear end rides pretty low. As long as I keep my body way up front I'm fine. However, when I get tired and my butt moves back an inch or two on the seat (it doesn't take much really) then the rear end sags and I can no longer hold a tight line in the turns. I put that on the account of the stiff BV stack and high oil level. I never thought about going stiffer on the rear spring... I'll see how it feels after I soften the BV.

Marcus, to reduce the preload I backed off the rebound clicker ass'y 3mm on the damping rod. In stock form, the clicker ass'y was threaded all the way onto the rod and that's in that position that I measured 6mm preload. The clicker ass'y is not threaded all the way to the bottom so I figured I could back it off 3mm and still keep about the same thread surface in contact with the rod. Also, I made sure that the small "D"-shape rod (that connects the adjusting screw to the needle inside the damping rod) would not disengage with clickers full in or full out.

Yoken this is not the way to reduce the spring preload.
Although you have kept the d-shaped rod in contact with the adj screw and needle. I would be a bit concerned if you didn't tighten up the locking nut tight against the center bolt assembly. I have seen individuals try and keep a gap between these too, which resulted in either a new rod or a center bolt because it pulled the threads, This might not be your case but if it is, I wouldn't ride it.

Russ

Posted by: marcusgunby---------------------

Yoken interesting way of chaing preload, liek russ says a little scary, i guess it might be ok as it does have alot of threads.

Posted by: steve125---------------------

I wouldn't chance it either, not for just 3mm of preload. You would be hard pressed to feel that anyway.

Posted by: Yoken---------------------

Thanks guys, now you got me worried and I'll have to check those lock nuts again before I ride... I must say that the WP of my old KTM520SX was a lot more convenient to adjust preload. Adding or removing spacers under the fork cap and fine-tuning at the track with the external adjuster was pretty cool!

Steve125, I think you can feel the difference between 3 and 6mm preload when you ride. I remember playing with the external adjuster of my KTM520. A couple turns - which was about 2 to 3mm of preload...if I remember well (Marcus please correct me if I'm wrong) were very noticable especially when accelerating on choppy hardpack terrain. With less pre-load the ride was more "comfortable" with less vibration transmitted to the bars... but I'll have to confirm this on the Showa though... it's not WP!

Now to increase preload, I guess the easy way would be to use spacers underneath the spring. But how do you guys reduce it ? I can't think of too many options :
- shortening the spring ?
- cutting another groove on the cartridge 3mm above the stock one and move the stopper ring up ?
... or do I really miss something ?

Posted by: bclapham---------------------

dont worry about the preload, just bolt up thefork as it should be and then tune with the valving. remember, if you stiffen the rear end it will put more bias back onto the fork. like everyone says, not using all them threads is asking for trouble. IMO, once you start messing with the mid and preload and all the other bits etc etc you have more things changing than you can keep track of. I spent a day testing with a pro on a 05CRF450 and a factory suspension tuner- once we had a baseline spring setup and valving, its amazing how much fine tuning was done with sag adjustments and moving the forks up and down in the triples, we revalved both ends twice at the track, but the clickers always stayed in the same spots. If i remember right, we went one up on the main spring and one down on the ICS.

Posted by: marcusgunby---------------------

I think you can feel 3mm on a showa but there is no easy way to reduce it that i know of-so i tend to stick with what it has and tune from that.

Posted by: steve125---------------------

I agree with Bruce, better to work with rear sag and fork position in the clamps, than the internal hassle for just 3mm of spring preload.

Posted by: russ17---------------------

Quote:

Now to increase preload, I guess the easy way would be to use spacers underneath the spring. But how do you guys reduce it ? I can't think of too many options :
- shortening the spring ?
- cutting another groove on the cartridge 3mm above the stock one and move the stopper ring up ?
... or do I really miss something ?

As bruce mentioned the ICS .It's purpose not only effects the overall spring rate, but effects spring preload also.

As others have stated I would get your numbers right with the rear spring (ie. sag) first.
Here is a good article:
http://www.mx-tech.com/articleread.asp?ArticleID=20
Russ

Posted by: Yoken---------------------

Thanks again to all of you for your valuable input. I just received the shims I ordered from MX-TECH... ordering was just easy, fast and trouble free!

So I plan on making my first revalving step this weekend (softening the bleed stack and the BV). Also, I'll follow your advise and screw the center bolt back where it belongs... I'll get back to you guys after my next ride.

Have a great week,

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Fork shim stacks for 05 CRF450

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