CRF250X - My Fork Stack Mods, need advise


40 replies to this topic
  • H-B-R

Posted January 10, 2014 - 01:49 PM

#21

important is use soft fork spring with more preload, bike will start stiff and finish soft.

 

 

Does the reverse apply - heavy spring with minimal preload starts soft and finishes stiff?



  • bowser

Posted January 10, 2014 - 02:12 PM

#22

Does the reverse apply - heavy spring with minimal preload starts soft and finishes stiff?

 

no, think about it this way

a light spring of 0.42N/mm with zero preload needs 0.42N to start and continue to move each mm of travel, meaning as soon as the spring has 0.42N it will start to move.

now dial in a some preload in the same spring giving it an equivalent rate of 0.50N/mm, meaning it will take 0.50N to start moving but once it does it will continue to move with only 0.42N of force.

 

now think about a heavy spring of 0.50N/mm, it take 0.5N to start and continue to move, is impossible to get it any lower by having zero preload



  • trekxrr

Posted January 10, 2014 - 08:37 PM

#23

trekxrr your from Aus, have read several of your posts on dirtbikeword.net.
You posted a similar BV stack on the CRF250X 2008 thread, recall you where using Goldvalve G2R valves at the time.
Does your stack need Goldvalves to work?

Never used G2r valves ,this setup is with stock valves!

  • cardinale199

Posted January 11, 2014 - 03:07 AM

#24

thanks  bowser i cant explain better cause my english is not good



  • H-B-R

Posted January 11, 2014 - 06:52 AM

#25

no, think about it this way
a light spring of 0.42N/mm with zero preload needs 0.42N to start and continue to move each mm of travel, meaning as soon as the spring has 0.42N it will start to move.
now dial in a some preload in the same spring giving it an equivalent rate of 0.50N/mm, meaning it will take 0.50N to start moving but once it does it will continue to move with only 0.42N of force.
 
now think about a heavy spring of 0.50N/mm, it take 0.5N to start and continue to move, is impossible to get it any lower by having zero preload


Thanks, makes perfect sense.

  • cardinale199

Posted January 11, 2014 - 10:40 AM

#26

thats why i prefeer soft spring and 10-14mm preload on woods.



  • bowser

Posted January 11, 2014 - 01:54 PM

#27

thats why i prefeer soft spring and 10-14mm preload on woods.

 

I'm the opposite, the primary purpose of the spring is to hold the rider up and use valving for damping. 



  • cardinale199

Posted January 11, 2014 - 10:19 PM

#28

remember spring are load sensitive, damping is speed sensitive , very different feeling



  • Van Wick

Posted January 12, 2014 - 03:30 AM

#29

i also use a 20mm plate exchange of oem 30mm bigger

 

What effect does modifying the BV base plate from 30mm to 20mm have on the fork action?


Edited by Van Wick, January 12, 2014 - 04:11 AM.


  • cardinale199

Posted January 12, 2014 - 11:25 AM

#30

not a big difference , only better oil flow,thats why new fork come with little plate



  • Van Wick

Posted January 12, 2014 - 11:48 AM

#31

not a big difference , only better oil flow,thats why new fork come with little plate

 

I'll machine some new 20mm x 2mm base plates and give it try.

 

Cardinale199 On the Fork and Shock stacks you gave me to try in post #4, what clicker settings should I start at?

 

Fork

Comp:

Rebound:

 

Shock

Race Sag:

LS Comp:

HS Comp:

Rebound:

Shock Bladder PSI: ???


Edited by Van Wick, January 12, 2014 - 12:23 PM.


  • cardinale199

Posted January 12, 2014 - 01:27 PM

#32

fork comp 12

fork rebound 16

 

race sag 105-110

low speed comp 12

hs comp 2,5turn

rebound 16 out

10 bar  around 150psi



  • EnglertRacing

Posted January 12, 2014 - 03:42 PM

#33

yes u can flip hs stack also , i prefeer using 12.30x3 but wil be similar, i also use a 20mm plate exchange of oem 30mm bigger

important is use soft fork spring with more preload, bike will start stiff and finish soft.

0.46 4mm
i prefeer 0.44 10mm


Weird I prefer .50 springs with 3mm preload
On a lighter 09crf450r that I use for everything, desert, trails, moto.


I think the op should try some .48 or even .50 with minimum oil level.

  • cardinale199

Posted January 12, 2014 - 11:16 PM

#34

this treadh start for 250x thats why i suggest 0.44

on your bike i like 0.47 with 12mm preload then 0.50 with 3mm but every rider like different feeling.



  • Van Wick

Posted January 13, 2014 - 02:58 PM

#35

fork comp 12

fork rebound 16

 

race sag 105-110

low speed comp 12

hs comp 2,5turn

rebound 16 out

10 bar  around 150psi

 

Grazie Cardinale199, apprezzo tutti i consigli



  • cardinale199

Posted January 14, 2014 - 12:35 PM

#36

have funny riding

and give a feedback to all



  • gman255

Posted January 14, 2014 - 03:01 PM

#37

VanWick- your stacks are using the oem 1.5 IC spring?



  • heart_of_darkness

Posted January 14, 2014 - 05:43 PM

#38

I think the rebound clicker functions as a free bleed in both the forks and shock. so backing the rebound further out also softens the compression. If you're intentionally running the rebound too fast, that sounds as if your compression stack is too stiff.

Maybe try a conventional two stage stack with much softer high speed valving.

31.1 (12)
23.1
29.1
27.1
25.1
23.1
Etc. on down to a 12 or 14 clamp.

Try matching that base valve to your mid valve stack but with 0.25 float. That's similar to what I'm now using.

  • Van Wick

Posted January 14, 2014 - 10:46 PM

#39

VanWick- your stacks are using the oem 1.5 IC spring?


Yeah still running the stock IC Spring.

Believe you can change them out for small bump compliance. I'm trying to dial my suspension in for rocks, more slow technical riding which is more hi speed and mid valve. Main issue was deflection.

Any benefit in changing out the ICS for these conditions?


  • YHGEORGE

Posted January 15, 2014 - 09:02 AM

#40

Yeah still running the stock IC Spring.

Believe you can change them out for small bump compliance. I'm trying to dial my suspension in for rocks, more slow technical riding which is more hi speed and mid valve. Main issue was deflection.

Any benefit in changing out the ICS for these conditions?

Tuners have used four different IC springs on my CR used for woods riding. I could tell no substantial difference.







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