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2015 KTM250sxf New Suspension Causing Knifing

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I just had my 2015 ktm250sxf resprung to my weight, 145lbs. The forks were revalved as well, according to my suspension guy I have a 4,4 (front) and 50 (rear). The only other change he made was raising the forks in the clamps quite a bit. looks like they are raised about 1/4in or maybe 1/8.

 

NOW HERE is where the issue is. Before having the suspension work done I was confident on my bike even though it was a harsh ride. Now the front end feels like it wants to knife, "jack knife". I've been ridding Florida sand for 15 years and never experienced it this bad. Even on the straights the front end wants to wobble and dig in. If I drop low into a whoop/roller the front digs in and knifes throwing me off. It feels like I used to have a steering stabilizer, and now I don't. I am constantly fighting the bars to stay straight and knife and wash out, which is causing arm pump and zero confidence in my bike. I'm thinking it might be because the forks are raised in the clamps, and or I'm just not use to soft suspension.

 

Any which way I would appreciate any input seeing as I spent a bit on the suspension work and hate it compared to 20lb heavier stock sprigs. It is very frustrating to want to go back to my old set up. If I am missing any info need to help solve this problem let me know. This is my first post and issue with my bikes over 15 years.

 

Thanks everyone!

Edited by elyk2391

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Seems like an easy experiment would be to lower the forks in the clamps. Generally you would want them lower when riding sand. All of the symptoms you listed can be a result of having the forks higher in the clamps.

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Would flush with my clickers be appropriate? I was reading that raising the forks in the clamps would stabilize it more so thats why I left it.Any other suggestions on how I can stabilize the front? Wouldn't lowering my forks throw my sag off a little? Thanks for the help.

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Why are you not asking the tuner about a solution? That is the first thing I recommend. LOWERING the forks in the clamps will increase stability,,,not raising them. Free experiment.

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I spent 4hrs with the tuner trying to figure out why it wanted to knife. Only thing we didnt change was fork position.

So you are saying if the clamp is flush with my compression dials I will have more stability? There is about 8mm sticking out of the top of the clamp.

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8mm is way too much for sand ,was it like that before?

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Yes, lower the forks in the clamps for more stability. If you are still having the front tuck under after that, I would put in one of the Oem heavier springs. See if you are possibly under sprung....

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It was flush before the adjustment. The springs are correct for my weight. Ill drop the fork so they are flush again. Anything else that may help stability so bars don't knife?

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Increase sag in the rear. If that doesn't work install one of the stiffer fork springs like the addict mentioned. You may need to reset the sag if you do.  All changes require some additional adjustment. Susp seems to always be a work in progress.

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It was flush before now you have 8mm showing ,this is a massive change,put them back to flush

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If relocating the forks back to flush tops doesn't completely solve your knifing issue, you may have too much rebound damping holding the front down. You may want to back off the rebound clickers to experiment. Make one of these adjustments at a time to avoid confusing the issue.

Good luck!

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George, what should I ncrease my sag to? 110 ?

Experiment to suit the "feel" you like, maybe a single revolution of the preload at a time then ride to see the result. In the end, what you like best determines the number. Good luck. Motorock makes an excellent point also.

Edited by YHGEORGE

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Thanks every one. I feel confident I'll be able to fix the issue this weekend at the tracks.

Thanks to all that had great input. Really like the idea of one revolution and a

Ride 5 laps. Then change one more revolution, and obviously only make one change at a time.

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Just to make sure my suggestion was understood.

1. Reposition the forks to flush with the top of the triple clamps, as Mog suggested. Meaning, the top of the silver outer fork tube, not the black upper-most part which should still extend above the top triple clamp.

Make no other changes.

Ride and evaluate.

If you like it, you're done.

If it still knifes.

2. Back off your rebound "CLICKERS" one or two clicks.

Make no other changes.

Ride and evaluate.

Repeat as necessary, one adjustment at a time.

Keep careful notes.

Sorry, I'm only vaguely familiar with WP forks. It sounded like you were going to adjust the spring preload. Backing this off will only increase knifing tendencies since it softens the initial fork travel resulting in a lower front end. This is the opposite of what you're trying to accomplish. This can be TIGHTENED for more preload to give you a higher front end to reduce knifing. Again. Single changes. Ride. Evaluate. Repeat.

Just wanted to make sure.

Best of luck, and please let us know how this turns out.

Edited by motrock93b

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I appreciate you clarifying, and i did adjust so i have 2mm sticking out of the top clamp instead of 8. I also increased my sag 5mm. Ridding tomorrow so I will be sure to let everyone know if that solved the knifing issue. Thanks for everyones input.

In simple terms I figured the higher the front end, the more stable, and the lower the front is the better for cornering. Have to find the equal medium.

Edited by elyk2391

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In simple terms I figured the higher the front end, the more stable, and the lower the front is the better for cornering. Have to find the equal medium.

 

Don't we all!

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Also sounds as if the rebound is too slow on the fork, go out counterclockwise with the red knob a couple of clicks to see if it improves.

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