Devon TRF Group Forum

Big T · Expert

WRF250/450 rear shock, possibly YZ/YZF?

trackman · Clubman B

Hi do you know if the shock is the same as a 2008 model because I think mine is to hard for me 12.0st ,cheers John.

Jerry atterick · Expert

If you go to Yam parts, as in Fowlers for example, you can x ref all Yam part numbers.
Similarly any of the after market spring manufacturers will x ref weight of rider / spring rate etc.
I think, but dont quote me, Yams are set for 10.5 stone rider.
Either way, when you set up your sag, if the spring is too hard, you wont get the required 100 - 110mm sag.
(Thats back of the bike not belly)
MX about 100, trail riding 110, similarly softer spring for trails and harshness on trails, back off compression and rebound less so.
At the end of the day you want a comfortable ride on the trails, if you want to go down them flat out then you will need to set up as MX.
But there again thats for ****s, Id never do that. Tee hee.

devondan · Champion

Part numbers here : www.partzilla.com/parts/search/Yamaha/Motorcycle/2003/WR250F+-+WR250FR/REAR+SUSPENSION/parts.html

kiwi · Clubman B

I got a spare rear spring could do at half that price

Jerry atterick · Expert

Other things to think about - feeling harsh / solid / dead ride.
Suspension linkage not 100% free and lubed.
Springs, when old, effectively case harden and loose a percentage of an even spring.
Shock settings too hard.
Rear shock absorber gas pressure too low, Ive had brand new race bikes that have been delivered at 50%, so worth checking.
Rear shock oil needs replacing at times, ie when serviced (Stating the obvious), everyone changes the fork oil but not so often the rear.
Front end as above.
I know its stating the obvious but a lot of people overlook the "back to standard and perfect" before moving onto "the problem".
Its no coincidence that if you ride an old MX bike, you think "This is awful, the new ones have moved on so much".
No, when new, they were a lot closer to modern than you would think.
Its mostly down to a sum of the above.
Anyways, hope you sort it.

Big T · Expert

Jerry atterick wrote:
Other things to think about - feeling harsh / solid / dead ride.
Suspension linkage not 100% free and lubed.
Springs, when old, effectively case harden and loose a percentage of an even spring.
Shock settings too hard.
Rear shock absorber gas pressure too low, Ive had brand new race bikes that have been delivered at 50%, so worth checking.
Rear shock oil needs replacing at times, ie when serviced (Stating the obvious), everyone changes the fork oil but not so often the rear.
Front end as above.
I know its stating the obvious but a lot of people overlook the "back to standard and perfect" before moving onto "the problem".
Its no coincidence that if you ride an old MX bike, you think "This is awful, the new ones have moved on so much".
No, when new, they were a lot closer to modern than you would think.
Its mostly down to a sum of the above.
Anyways, hope you sort it.

Thanks - without being an 'expert' myself, the main issue I have is that I have had to preload the rear spring almost to the end of the thread in order to get the sag about right. In my mind, this will restrict the amount of additional compression available, as well as still being soft over the rest of its travel. I don't have any specialist tools for checking pressures, nitro-charging etc, so may have to get somebody to do this for me. I've been having a play on a local MX track, and the suspension compresses right down over jumps. Although most of my riding is trails, I'd like to firm it up for occasional track use (as a compromise, as I wouldn't want to be swapping things around too much).

Big T · Expert

A friend (lighter than myself) has just had his YZF sorted as it was too firm for him, leaving a spare (stock?) spring which I could compare to what I've got. Is there an identification mark on these springs anywhere or is it necessary to rig up some device to measure spring rate?

I've just checked some measurements, based on instructions from here: http://motocrossactionmag.com/mx-education-how-to-select-the-correct-rear-shock-spring/

STEP FOUR: HOW TO CHOOSE A SPRING RATE BASED ON THE STATIC SAG NUMBER

Static sag should be between 30mm and 40mm on big bikes (125, 250 or 450). If you have more than 40mm of static sag, your shock spring is too stiff. That may sound wrong, but it is right. If you have less than 30mm, then your spring is too soft. Its that simple to determine whether your shock spring is right for your perfectly toned and trained torso. Lets recap:

(1) Set your race sag at 100mm.

(2) Measure how much your bike sags without you onboard.

(3) If it sags more than 40mm, go to the next softest shock spring.

(4) If it sags less than 30mm, go stiffer.

(5) If you are on the cusp, make a judgment call.

After setting 100mm race sag, I only have 9mm static sag, confirming I need a stiffer spring.