Help with WP Extreme 50mm...

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Aug 28, 2000
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#1
After riding a track the other day for the first time I noticed the forks on my Husa were blowing right through the stroke, more or less, and bottoming...not hard but hard enough for my puny airs!

I pulled the forks off this morning, removed the spring, removed the cartridge, emptied the oil...got about 500ml dumped out and maybe another 50-100ml on the bench & rag from the cartridge. The manual said I should see about 750ml, is this right? If so, I was down on fluid some to begin with.

The previous owner had cut the springs down about 1 1/2" and replaced with PVC shim of about 1 1/4" . I have the stock springs that he gave me too, that's how I know how much was cut down, the stock ones are 1 1/2" longer. I am wondering if this isn't adding to the harshness some? I am considering putting the stockers back in and maybe 20mm of preload shim. I am 205 lbs. now (down from 245!) and raising the oil height to 120-130 mm, stock is 150mm. Mostly riding trails, and some jumping, nothing huge....yet.

Also, if I am changing to Mobil 1 ATF, do I need to totally disassemble the cartridge and clean it before I refill with the new? Or will the little residule fork oil mix okay with the synthetic? This is my first time tearing into forks so I didn't want to get too carried away just yet. :eek:
 
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#2
WP 50's

If you are bottomimg with the shorter( and stiffer!) springs in, then putting the longer stockers in will make it even softer. The questions to answer are how much preload on the springs, where were your clickers set at,what oil weight was in the fork(stock is 5wt) and what do you want the fork to do. I would leave the stiffer springs in with around 5mm preload, try a 7.5 or 10 wt. oil, and play with the compression clicker on the left fork leg. Rebound is on right. There is a world of difference in feel from full soft to full hard on clicker.

01 520 mxc
98 200 mxc
 

DanS

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Dec 6, 2000
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#3
You might not want to go higher than 140mm on the oil. 160mm-140mm is listed as the range. I would think that by cutting the springs shorter it would make them harsh especialy if they were stiffer. I put new springs in my '99 300exc and they were longer and stiffer than stock. Had to cut the spacer in half to get 8mm's of preload. Made a big difference in how the forks work. Very plush on small high speed hits yet soak up big landings without bottoming. I use Moble 1 ATF (about 7.5wt) at 140mm. Try getting the right springs and see how that works. After that you may want to consider having the valving redone.
 
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#4
Thanks!

I went ahead and just cleaned everything up, did not take the cartridge apart this time. Is there any trick to this for next time or pretty straight forward?

I put the stiffer springs back it for now and filled with ATF to 130mm. My manual said you can go as high as 120mm.

This was really just a "get aquainted" disassembly of the forks. I feel better about tearing into them in the future and proceeding with the cartridge & possibley some shims & valves.:scream:
 

DanS

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#5
Must be a different version of the fork than what my KTM has if your manual says you can go to 120mm. Raising the oil level will only affect the last part of the stroke before it bottoms. MX-Tech is supposed to have a low flow piston and valving setup that really improves the WP forks. They are doing my shock right now. I would still try springs for your weight that are the right length.
 

Jeremy Wilkey

Owner, MX-Tech
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#6
Scott,
The fork on intial view are very old and antquidated, however upon spending lots of time with them, I was riding a 99KTM 125 SX this spring I've come to have a much deeper respect. The 21mm Cartridge is small but the design made it very leak free and hence efficent. The adjuster mechaims is very well designed. The area of the rod, cartridge, and bleed orfice are such that the adjuster controls about 20% of the displaced fluid making the fork very adjustable. IF WP had put basevalve bleed adjustment the fork would have been opne of the best ever.. Amazinly even with 21mm cartridges. The slap down action was awesome..

I used to bash the Extreme fork till I was forced to make it work.. When I was I really realized I was not seeing outside the box..

Regards,
Jer
 
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#7
Mods?

Jeremy,

Thanks for your input, as always. Do you actually modify the cartridge or are talking about making it "work" with alternative valviing? My love affair with this bike is on & off, so not sure whether I will keep it another season or just jump on KTM or something with more modern suspension. I do love that Ohlins shock, even stock it feels great. Can you help me out with parts for these...provide a shim stack, valves, seals, etc.? I was surprised at how simple they are inside, glad I made an effort to tear into them.

There just seems to be a lot stiction in the forks once mounted up. I've been careful not to over tighten the t-clamps or the fork protector clamps, but just not real plush feeling in general, even with the softer, stock springs I reinstalled last night.