How to make stock fork stiffer xr650r


6 replies to this topic
  • dydko

Posted February 28, 2006 - 01:39 PM

#1

Plese help me ?
I've read that is possible to make the BRP fork much more stiffer than stock
by cutting factory springs and mouting the spacers. Im looking for instructions how to DIY , pictures links anything . Help me
Thanks

  • Modsport02

Posted February 28, 2006 - 04:23 PM

#2

uhh thats ghetto as hell, just buy stiffer fork springs and oil!!

  • Old_Man_Time

Posted February 28, 2006 - 04:59 PM

#3

Here is your link:
http://www.off-road....ech/2002spring/

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • JackAttack

Posted February 28, 2006 - 05:45 PM

#4

uhh thats ghetto as hell, just buy stiffer fork springs and oil!!

What is "ghetto as hell" about cutting the springs and adding a spacer?

It appears the dude lives in Poland and is probably running a supermoto bike.

If you don't have something positive to add then go back to the wr450yamaha forum. :thumbsup:

  • sorenlaf

Posted March 01, 2006 - 07:28 AM

#5

Plese help me ?
I've read that is possible to make the BRP fork much more stiffer than stock
by cutting factory springs and mouting the spacers. Im looking for instructions how to DIY , pictures links anything . Help me
Thanks


That will work. Any time you shorten a spring it gets stiffer.

If it's a straight wound spring, the effect is linear. Half as long is twice the spring rate.

E.g. if is a straight wound spring, 10" long, with a spring rate of .8kg/mm and you want a spring that's .9kg/mm, you need to shorten the spring to 10" (.8/.9) or 8.9"

There is a downside to this, if you shorten the spring too much, it will "coil lock." That's when the spring compresses to the point where the coils hit each other (which is how a progressive spring works; the soft end coil locks, leaving only the stiffer end).

If it's a progressive spring, then it matters which end you remove coils from, and the above relationship doesn't really hold well. The plus side is that you can probably get more benefit and lose less travel by removing the soft coils - these are the ones spaced closer together.

Basically, you need to measure all the "free" space between the coils. That free space must be greater than your suspension travel **AND** your spring preload (not the spacer distance, just the preload - basically how much you need to compress the spring to get the fork cap on), or it will coil lock. I suspect that you should have some buffer above the coil lock point, but I have no idea what that would be.

You may also cause the spring to fatigue sooner, as it's going to be compressed more than the designer intended. Probably better to just replace the spring.


--Soren

  • hill5150

Posted March 01, 2006 - 12:04 PM

#6

Just have a professional do the revalve and springs, it will cost you 400.00.It's worth it...................Plus you don't have to worry about contaminating your cylinders unless you have an operating room....

  • dydko

Posted March 01, 2006 - 12:41 PM

#7

Thanks You all for your replies.
Now I now that the best way is to buy new springs, but as JackAttack noticed Im living in poland and the BRP is rather rare bike in our country and the only one way to buy springs for it is to buy it in US. I will try to change the oil if it wont help I would buy spring from US.
Thanks





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