Forks deflecting, not staying planted

[Berm-Saw]

2006 crf250r

 

Trying to get this old thing dialed in. The forks aren't wanting to play nice. Doesn't wanna go where I point it regardless of playing with sag and fork length in tripple clamps. Defanitly does not feel like I'm riding on rails.

 

150 pounds street cloths

 

.43 in the forks, also have lighter comp springs. Only about 320cc of oil

 

4.7 shock spring.

 

Fc recommended .43 and 4.9...already ditched the 4.9 shock spring for a 4.7 Sag numbers weren't good with the 4.9. Now in order to cure this I think I need lighter fork springs. Maby.41 as I don't have very much oil in them so I can be using more of the stroke. Bike isn't really rideable on a mx track at the moment. Its pretty horrible.

[Serg528]

Has it been revalved yet, ive had good luck with .42 with my light riders. you did good changing comp spring. 1.6 im assuming. 22mm offset triple clamps help alot with 06 crf250r if turning is your issue. again if not revalved do that first.

[tom02cr250]

Revalving it softer will help alot. Did you try opening up the compression clickers a few clicks? What are they set at?  Is it rebounding too fast? 

[Hans Schmid]

When's the last time they had a service? 

[mlatour]

As Monk suggested, when were they last serviced and,

especially the ISC piston rod seals which in this model of fork seems more prone to wearing out.

bad seal: cavitation, lack of damping

 

Also, have you measured the spring preload ?

1-2mm makes a noticeable difference on how the front end handles.

Edited April 6, 2017 by mlatour

[mog]

The valving is stiff std

[Berm-Saw]

I have revalved comp assembly. But don't know by who or what the purpose was intended for.

Serviced the ics and changed all oils last spring. They are fresh

Comp clicker is opened up a lot I know. Gonna fool with the rebound more before I spend money I guess

[Berm-Saw]

Slowing the rebound helped. Next question would be would I benefit from softer springs since I have comp almost all the way soft, reb all the way hard, and the minimum oil in the forks. I don't think I'm worried about it being to soft since I just pretty much ride off road and not mx tracks much. Also I could just add some oil.

[tom02cr250]

Yes you'd benefit from softer springs and softer revalving 

[mlatour]

My friend rides a 2007 CRF250R, he's about 5'6" & 130lbs at most,

usually riding MX only but now wanting to ride trails on occasion

last winter I converted his suspension to the same settings as my CRF250X,

meaning with .42kg/mm & 4.8kg/mm springs, X valving specs and lighter ISC springs as well.

 

This past summer his shedule didn't allow him to trail ride but, the few MX tracks days we did,

it was discovered the softer settings were a great improvement for MX'ing as well.

(experienced rider but recreational motocross riding, 'vet' track style / mostly tabletops)

 

 

Edited April 6, 2017 by mlatour

[Berm-Saw]

 
Also, have you measured the spring preload ?
1-2mm makes a noticeable difference on how the front end handles.

How do I check this?

[Berm-Saw]

My friend rides a 2007 CRF250R, he's about 5'6" & 130lbs at most,
usually riding MX only but now wanting to ride trails on occasion
last winter I converted his suspension to the same settings as my CRF250X,
meaning with .42kg/mm & 4.8kg/mm springs, X valving specs and lighter ISC springs as well.
 
This past summer his shedule didn't allow him to trail ride but, the few MX tracks days we did,
it was discovered the softer settings were a great improvement for MX'ing as well.
(experienced rider but recreational motocross riding, 'vet' track style / mostly tabletops)
 
 

Would I need to buy shims to revalve to X specs?

[mlatour]

Link:

https://www.google.ca/search?q=measuring+fork+spring+preload&ie=utf-8&oe=utf-8&gws_rd=cr&ei=AAXnWO6JNYHSjAOZ05WQAQ

By memory, about 7mm of preload was common for both CRF's I've tinkered with,

I've reduced mine in the 4mm range since I mostly ride low speed / rocky trails and looking for a plush ride (no jumping/hard landings)

You might have to cut down the spring perches or remove some spacers (if applicable).

My YZ also had a front end washout issue until I reduced the preload.

 

As for the valving, by memory you remove a few face shims

and yes you'll need some 14.2 and 16.1 shims as the 250R uses a 18.1 final clamp shim.

 

I'll PM you a list of both my 250X and friend's 250R modified stacks if you want.

[ossagp]

Good information.

[Berm-Saw]

Link:
https://www.google.ca/search?q=measuring+fork+spring+preload&ie=utf-8&oe=utf-8&gws_rd=cr&ei=AAXnWO6JNYHSjAOZ05WQAQ
By memory, about 7mm of preload was common for both CRF's I've tinkered with,
I've reduced mine in the 4mm range since I mostly ride low speed / rocky trails and looking for a plush ride (no jumping/hard landings)
You might have to cut down the spring perches or remove some spacers (if applicable).
My YZ also had a front end washout issue until I reduced the preload.
 
As for the valving, by memory you remove a few face shims
and yes you'll need some 14.2 and 16.1 shims as the 250R uses a 18.1 final clamp shim.
 
I'll PM you a list of both my 250X and friend's 250R modified stacks if you want.

Didn't find any specific info about the 06 crf forks in that link. The preloaded spring is the main spring right? Where are the preload spacers exactly?

Appreciate the offer on the valving specs but honestly I don't know much of anything about revalving. I'm gonna see if FC will help me out on the price if I only send them the parts they need for a revalve.

[texasthierry]

3 hours ago, Berm-Saw said:

 if I only send them the parts they need for a revalve.

 

If you dig to this point you are pretty close to do the all job yourself...

[mlatour]

To measure the preload, roughly explained:

remove the forks from the bike, loose top caps, dump the outer tube's oil

mount the tube verticaly by the axle lug in a vise using soft jaws

measure the total length of the extended fork, from top of cap to where the lower tube ends

 

remove the bottom rebound clicker assy, disconnect the rebound rod from it

the fork will now extend more, re-mount them in the vise, 

extend it and gently lower the upper tube until it just sits on the spring without compressing it,

re-measure the total length and deduct the earlier measurement, example, 887mm - 880mm = 7mm of preload.

 

If equipped, some large diameter aftermarket preload spacers are sometimes installed at the bottom spring seat 

(often included when buying Race Tech springs)  I've also read that bottom spacers are not the preferred way to tune fine preload.

 

Otherwise, there are thin washers/spacers in the upper spring perch assy you can remove, 

if not applicable, you can machine down the ends of the spring perches a few mm's reduce preload. (that's what I did)

 

Early CRF-X & R had very similar but slightly different spring lengths, something like 495mm vs 500mm,

meaning installing softer OEM 'R' springs in an 'X' can automatically increase the preload by 5mm

If you still have them, compare the length of you old versus new springs.

Edited April 7, 2017 by mlatour

[Berm-Saw]

Thanks. I may get back to you on the shim settings. FC is gonna cost arm and leg.

[Berm-Saw]

Where do I buy shims, and everything else I would need for a DIY revalve?

[mog]

Mx tech or race tech