How do u get rid of mid stroke harshness on crf250 2008?


13 replies to this topic
  • bunnet

Posted August 19, 2010 - 02:42 AM

#1

Hey all

As the title says how do you get rid of the mid stroke harshness in the front forks on a crf250 2008.

I have the right springs for my weight front and back.

It is especially prominent over sharp rough breaking bumps, feels solid just a couple of inches in the stroke.

I have tried various clicker settings, i can improve other areas but not the mid.

I have contacted k-tech in the uk, they advised me the pressure spring is a 1.9 and has not changed since 2004, this comment goes against what some people are saying about the pressure spring being increased in stiffness??? anyway they recommended 1.61 pressure spring for me.

Any ideas......?

Edited by bunnet, August 20, 2010 - 12:25 AM.


  • Charlie C

Posted August 19, 2010 - 11:23 AM

#2

I'm not a suspension guy and hopefully I can get this thread started for you, but you may have to have the mid-valve modified. Hopefully someone that knows for sure will chime in and correct me if I'm wrong.

  • aaronbellmx355

Posted August 19, 2010 - 05:22 PM

#3

have you tried a lower oil level? or maybe try going to a lighter weight fork oil.

  • 1st4stroke41

Posted August 19, 2010 - 07:16 PM

#4

My brother is a Pro-Action dealer, I'm sure he could help.

  • tidtid

Posted August 19, 2010 - 07:27 PM

#5

Before modifying the midvalve try going down on the pressure springs above the compression stack, the short spring that are about 4 inches long. This will make the forks alittle softer all the way through and also make the spike at halfway less harsh. Go to racetech.com and do product search and it will tell what is stock and what you need for you weight, you can also go lower if needed. Going to a lower pressure spring will alow the forks to operate at a lower pressure.

  • bunnet

Posted August 19, 2010 - 11:52 PM

#6

Some good points here. Thanks guys!

I have tried lowering fork oil but only makes a marginal difference. not tried a lighter oil weight.

I have posted the same question in the suspension section and got the following answer

(Posted by: EDS
On: 08-19-2010 08:48 AM

best way to solve it is to replace the '08 spring seat and spring on the mid valve with the '07 components

'08 mid valve spring is waaay to stiff, resulting in basically no blow off, which leads to the harsh mid stroke

you may need to revalve the compression base valve as well to get the action that you are looking for....

pm me if you need more help.)

There is consistency in replies about changing the mid valve and also the compression spring. Compression spring seems like something I can do and not too expensive so I will look into that and report back!

THANKS again guys this forum is such a good resource!

  • Charlie C

Posted August 20, 2010 - 05:25 AM

#7

Glad someone who really knows this stuff chimed in! Thanks for helping him out!

  • 36MotoMarc

Posted August 20, 2010 - 10:55 AM

#8

He's not refering to the compression spring, he's refering to the mid-valve check-spring, on the damper rod inside the cartridge, backside of the rebound piston. the "mid" valve.

I pulled a shim from my mid-valve providing more float and less preload. It's way less harsh, but for me it blows through and bottoms too easily, not perfect for me.

Softer compression springs aren't all they are cracked up to be. That spring simulates the nitrogen charge in a shock, and going lighter on it can allow unwanted cavitation unless the valving is lightened up, also.

  • love mx

Posted August 22, 2010 - 10:58 AM

#9

what shim did you remove?

  • 36MotoMarc

Posted August 22, 2010 - 04:37 PM

#10

Oh man it was 2 years ago but I believe it was the second one in, counting from the piston. You'll notice an immediate difference but if you're fast and/or heavy it will blow through on overjumps and sharp hits. I beilieve I ran 350cc in the outer chambers, and I also added one identical rebound shim while I was in the cartrige, .10 x 21 i believe? Been awhile. This lets you run the rebound adjuster screw out farther without loosing rebound control. A lesser rebound screw setting also reduces mid-valve damping, as it bleeds both ways.

  • tidtid

Posted August 23, 2010 - 05:56 AM

#11

If you don't want to try the lower rate pressure spring and going to change the mid valve I changed to a race tech setup. It has more float but a little stiffer spring on the midvalve I used 3 to 4 shims.

  • love mx

Posted August 23, 2010 - 08:13 AM

#12

As per EDS suggestion I have ordered a 1.67 pressure spring (1.67 was recommended by k-tech here in the uk ) and a 07 mid valve spring seat.

I have no idea how to remove shims so doing this 1st.

Will update with results. Still might give you a shout EDS if this doesn't work. I was going to call, and see what you had to say. If you were going to do a revalve I would have probably drop them off to you but I figured I wouldn't learn anything from that so going for the DIY :bonk:

  • love mx

Posted August 28, 2010 - 12:55 PM

#13

UPDATE

I have changed to a 07 mid valve spring seat and it has made a big reduction on the mid stroke harshness. started of with 320ml of oil but was bottoming to easily so now running 400ml and it has reduced the bottoming. Happy with the results so leaving it at that.

Thanks to everyone who chimed in!!

  • Pete Payne

Posted August 30, 2010 - 08:54 AM

#14

going from 320ml to 400ml was one huge step





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