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YZ fork spring pre-load.

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I'm working on my '01 YZ250 and it was recommended for me to check fork spring pre-load.  The manual really doesn't say anything about it.  I think you compress the spring a little when you screw on and tighten down the fork cap and spring seat parts on the dampening rod.  I think you also compress the spring a little when you tighten the fork cap down on the tube.  If this is correct, then do you add those 2 amounts?  I was told it should absolutely NOT be more than 4 mm. and I think mine has been more than that but I've never actually measured it.

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If you have OEM springs you shouldn't have any IIRC. Said something in the manual about available preload spacers added to the bottom of the spring. Never used them myself.

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Just take the uncompressed spring and measure it ,then with the cartridge on the bench ,fit the spring and measure it again

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Just take the uncompressed spring and measure it ,then with the cartridge on the bench ,fit the spring and measure it again

I'll try that but don't you also compress it a little when you screw the cap onto the fork (with the spring, of course) ?

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Yes that's the way to get the correct measurement

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OK, I measured spring free length - a no brainer.  Next I put the spring on the dampening rod assy., put the fork cap parts on and tightened it up so I could measure the installed length.  No problem.  What I don't find too easy is when installing the spring in an assembled fork tube and tightening down the cap, it's kind of hard to tell when you are actually compressing the spring and/or when the cap is simply screwing down to seat itself..  

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I think I understand what you're saying, however I think you're overthinking it. Since you're pulling the outer tube up to the top cap, it should have no effect on the preload of the spring.

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I think I understand what you're saying, however I think you're overthinking it. Since you're pulling the outer tube up to the top cap, it should have no effect on the preload of the spring.

I know I have been accused of over-thinking things sometimes BUT when you're screwing down the cap, the bottom of the spring is stationary.  It's on it's bottom seat.  When you screw the cap all the way to it's stop, part of that last 1/2" to 3/4" DOES compress the spring.  I can feel the lower fork tube starting to get a preload tension when I screw the cap home.  I look at that as part of the total pre-load.  

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When screwing the top cap on to the damper rod should be considered in your total preload. Screwing the top cap to the outer tube should not.

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When screwing the top cap on to the damper rod should be considered in your total preload. Screwing the top cap to the outer tube should not.

K- Thanks.

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