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Fork spring preload causing knifing ?

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I have a 2014 crf 250 with race tech springs and gold valves . The issue I am having is knifing on the front end and a feeling of a un Balanced front end . I have spent a day with my suspension tuner and he thinks that this issue could be caused by the 4mm preload on fork springs . What are your thoughts ?

148 pounds Novice rider set up for Mx

4.2 springs , 350cc oil. Com 14 felt best , reb 14

Rear shock 4.7

rear sag set at 102

Edited by AdamRm

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First thing ur springs r to stiff for u, that bike be better with a little more sag on the rear, at 105mm of sag I bet u could turn the spring round with ur hand, no preload on the spring at all. If uv had revalve and ur rebound is at 14, there's to much damping still in the fork. And 4mm of preload won't cause u any problems, I would say. Those springs be suited more to 70-80kg I would say softer springs and a revalve is what u need, so u can run bit more sag,

Edited by karlace

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U could also try moving forks through the clamps aswell

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First thing ur springs r to stiff for u, that bike be better with a little more sag on the rear, at 105mm of sag I bet u could turn the spring round with ur hand, no preload on the spring at all. If uv had revalve and ur rebound is at 14, there's to much damping still in the fork. And 4mm of preload won't cause u any problems, I would say. Those springs be suited more to 70-80kg I would say softer springs and a revalve is what u need, so u can run bit more sag,

The springs I have recommended by race tech . I did just noticed that the adjustment on the rear shock is all the way to the top as it can't be Loosen any more

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As Karl said your springs are off , rt is not close enough on spring rates

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I thing even a 45nm rear would be to stiff, I got somone 68kg on 45nm rear he's over 40mm static.

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I think if u drop ur sag a little more, that will help with ur problem, didn't ur suspension guy tell u the springs r wrong , if he spent the day with u

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Crf linkage does require very soft springs

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Did it do it before the Race Tech revalve? What was your last bike and how long have you had the 14 crf250? 

Edited by ActiveRide

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My suspension guy did the springs and revalve at the same time . My last bike was a 2010 with race tech suspension by the same suspension builder . I have had this bike 4 months 40 hours on the race tech gear. I did not feel the knifing with stick suspension

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My suspension guy did the springs and revalve at the same time . My last bike was a 2010 with race tech suspension by the same suspension builder . I have had this bike 4 months 40 hours on the race tech gear. I did not feel the knifing with stick suspension

 

2010 CRF250? The 14 CRF250 is a front end heavy bike or "stink bug" bike (the front has a lot of weight on it). I asked that question because if you came of a Yamaha or Kawi, it could feel twitchy.  

 

My best guess is Race tech tuners tend to disable or drastically soften the MSV or "midvalve" and run two stage base valve valving. Which on the CRF250 can be hard to make work.  Ask him about it and see what he says. If he says MSV's are the devil, or he softened the fork dramatically, suggest making it stiffer to him "I want to try it stiffer". If he says he didn't change it much, ask him to try the next stiffer fork spring or MORE pre load (which hopefully he was suggesting) Tuners can be jerks with big egos when a customer suggests something, so if he argues, just say you want to learn and just want to try it. Tell him you aren't happy. IT HAPPENS.. it doesn't mean he sucks, it's just not what you want, and tell him that you don't blame him! If he is reasonable he will respond and it will help him learn about the bike. If he balks, or blows you off. Find another tuner.

 

In the mean time take weight off the front. You can do this in a variety of ways. Run the forks lower in the clamps (flush with hex fork cap) or increase sag. 110..115. If you don't have someone to measure, just count turns of the spring collar try two turns softer. You might not like the way it feels in other areas, but you are just doing it to look for clues and to see if the knifing goes away. Good luck.

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He has no preload on rear spring already

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I'd start by getting ur tuner to put u on the right springs first

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