89 yz250 forks and shock valving

Discussion in '2-Stroke Discussion' started by sr5bidder, Nov 18, 2009.

  1. sr5bidder

    sr5bidder Rookie DRN Member

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    I tried to ask over at TT but no luck
    I'm looking for wisdom on valving for the woods.

    I see the valving stack on the front fork parts fitche, but need to know if its as simple as removing X number from X stack or adding.

    I have no idea on the rear shock there is no exploded diagram and it needs new seals (availible from race tech) and I have never had a rear shock apart,,, lucky for me I have a friends bike to learn on :laugh:



    any help would be great
    :
  2. dirt bike dave

    dirt bike dave Sponsoring Member

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    Not sure about shims for your stack.

    As a general rule on MX bikes of that vintage, you will want to significantly reduce the high speed compression damping, especially on the forks.

    That change alone should make a big improvement in the woods.
  3. sr5bidder

    sr5bidder Rookie DRN Member

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    agreed but it looks as though there are two stacks, one atop the other at the bottom of the fork any idea's witch does what?
  4. julien_d

    julien_d Rookie DRN Member

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    New bike, or new forks? My buddy has an 89 yz250. I've found the forks to be pretty decent for the woods just after a rebuild. The valving is stock AFAIK. He had a shop here do the seals, bushings, and oil. That bike is a blast to ride in the woods if you can hang onto it, it has a nasssssty hit.
  5. sr5bidder

    sr5bidder Rookie DRN Member

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    AFAIK??????

    as you may well have expierence,, it's an 89 and who knows what has been done to it, it beat him pretty badly on saturday they are kyb 41mm usd stock, guess with all this info and help I can only tear into it blindly and take a few shims out and keep a note pad handy. I know he did the seals himself and is a noob so maybe he's go to much oil in them???

    thanks JD
  6. dirt bike dave

    dirt bike dave Sponsoring Member

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    Too much oil will increase bottoming resistance and stiffen the fork as it nears full compression.

    If it is way overfilled, he won't be using full travel and it will be overly stiff after the first few inches of travel.

    Oil level is a useful way to fine tune the suspension, but the damping is where the big improvements will be made.

    I'm not sure which part of your shim stack is the high speed part, but when you identify it, i'd be tempted to take several shims out and give it a try.
  7. julien_d

    julien_d Rookie DRN Member

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    AFAIK = as far as I know.

    The bike my buddy has was set up for MX and was raced frequently before it was retired and sat in some guy shed for a few years before it was given to my buddy. Yes, given. It was in shockingly good shape when we picked it up. He had hinted at passing it on to me since he was running an older KTM 300 at the time, but the YZ was in much better shape than his current ride so he kept it. Fork rebuild, top end, all bearings and bushings replaced, and it's a wicked machine.

    The 41mm usd's were decidedly lackluster for MX use. Simply too spindly. But for trail riding they have proven to be pretty smooth. On his bike, the clicker settings on the rear shock along with preload on the rear spring seem to affect the front suspension greatly, so check that for sure. If there's any grab or sticky feeling when compressing the front the bushings will likely need to be checked/replaced. I've seen some info somewhere on those forks for shim stacks, I'll have to see if I can locate it again.

    Here's my buddies bike before/after rebuild. I liked it better in purple/white personally, but he's a freak.... It's sporting yz125 plastics now, and a hacked up graphics kit from a blaster.



    http://www.bikepics.com/members/factorfreejack/89yz250/
  8. sr5bidder

    sr5bidder Rookie DRN Member

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    JD I like you and all but I'm on your buddies side on the before and after I'd have to say your the freak liking the purple and all,, that thing looks sweet in black and white!!!
  9. julien_d

    julien_d Rookie DRN Member

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    lol, yeah. It does look sweet in black and white. It's just that he wasn't patient enough to search for black and white plastics for the 250, so he bought later model yz125 plastics and we frankenstiened them on there. Would look MUCH better if the plastics fit properly, and the graphics weren't hacked up quad graphics. The frame was powder coated black, and the engine was sprayed with high temp graphite. We're gonna have another go at it one of these days with plastics and graphics...

    Nothing changes the fact that the bike is a blast to ride. The biggest problem is keeping the front end down.
  10. sr5bidder

    sr5bidder Rookie DRN Member

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    well we got the steering stem aprt (pita) removed the valving from the forks, from the top of the valves there was the nut, cup washer, spring, coller,shim, valve (looks like the one racetech pistures except dark gray color), large shim, very small shim, large shim, medium large shim, medium large shim, medium shim, medium shim, medium small shim, small shim, thick washer, then the valve body. Picture below...from the valve body we decided to remove shim #4..no testing has been done yet





    [​IMG]
  11. julien_d

    julien_d Rookie DRN Member

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    I know this was forever ago, but did you go any further with this? I'm wanting to play with the valving in my yz250 forks to make the more plush for single track. I never got around to asking you how it turned out.



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