Question about 2010 kawasaki KX 450F Monster Energy

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Hi..Im looking to get my 2011 KX450F suspension working right for my weight of 70kgs The forks seem way too harsh/choppy over small bumps at speed..doesnt help with arm pump .....Wanted to set the race sag to 105mm on the rear... Strangly my bike sag is at 40mm NOW and when i sit on it, race sag moves only 60mm.. Service book shows.. Rear STANDARD shock spring, = 54NM-5.7KGF.. Adjustable RANGE is 126mm-138mm (thats the TOP of the BOTTOM adjusting nut ('C') to shock top mount bolt centre) Its already set to 118mm..from shop i bought it from..:tears There is at least 4-5 threads left to soften the spring if possible?... How critical is the adjustable range? can i just soften the spring LOWER than 118mm,but just run the forks around 10mm from the top to compensate? Or is that a definate NO??:smirk: Seems a bit strange that there is 40mm sag and 60mm race sag... I was under the impression more SAG in milimetres would indicate soft spring!! :excuseme: If the spring is replaced for a lighter one the service book shows that you STILL have to have 126-138mm adjustable range... Confused.. Im looking to learn how to balance shock to fork ratios if you can simplify the process?? :cheers 70KGS rider!!

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Your going to have to keep working through the manual, it has way more info than can be typed here.
If it feels too hard and youre out of adjustment, you need to try a softer spring.
you can try anything that works for you, forks up, down, more or less sag, there is no quick simple fix and what one rider says is good may not work for another, and a different track may change things completely.
harsh front- reduce the compression damping, high speed or low speed depending on how far the forks are compressing or lighter oil, if you go too light it may try to tank slap and need a steering damper.
If you use all the travel, then the springs are close to correct, it can even bottom out a little on the biggest jumps

One step at a time and take notes of each change, including how it felt and what the track was like.. this is the way to see what works, and give you the option to easily change it back if it doesnt

Posted on May 23, 2011


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Just want to raise rear shock

Firstly, the best starting point for a suspension set up is the manufacturers original settings. This allows you to go back to a baseline set up, no matter how much fiddling around you do.

Because everyone is slightly different and of differing weights, then a bike will work best when set up to the individual. The following rough guide for a solo rider has worked on bikes I've owned to give me a good suspension set up for road use.

Initially we'll adjust the preload on the suspension.
The front preload:-
1. Put a cable tie round the front fork stanchion (the shiney bit).
2. Get help from a mate and lift the front of the bike, so there is no weight on the front forks, and slide the cable tie down the fork until it rests on the fork seal. If you've got USD forks, then slide the cable tie upwards to the fork seal.
3. Put the bike back on the ground.
4. Now wearing all your riding gear, get on the bike gently and allow your full weight to settle on the bike in roughly a riding position. Try not to bounce the bike as you do it. You should now be sitting there with your tip toes lightly on the ground stabilising the bike.
5. When everything is stable, get your mate to slide the cable tie till it again touches the fork seal.
6. Carefully get off the bike.
7. The front of the bike needs lifting again until the weight is off the forks. Now measure the distance between the cable tie and the fork seal. Ideally the gap should be in the region of 30 to 40mm. If the gap is too large then increase the preload and repeat steps 2 to 7, if the gap is too small then reduce the preload and repeat steps 2 to 7.

The rear preload:-
1. With the help of that same good mate, you'll owe him a beer after all this lifting, lift the back of the bike so the weight is off the rear suspension.
2. Measure from the centre of the rear axle to a fixed part of the bike above it. Remember this measurement as R1.
3. Put the bike back down.
4. Now wearing all your riding gear, get on the bike and allow your full weight to settle on the bike in roughly a riding position. You should now be sitting there with your tip toes lightly on the ground stabilising the bike.
5. Measure from the centre of the axle to the same point on the bike as before. Remember this measurment as R2.
6. Now the maths. R1 minus R2 should be in the region of 30 to 40mm. If it's greater, then the rear preload needs increasing and repeat steps 4 to 6. If it's less then the rear preload needs reduciing and repeat steps 4 to 6. The R1 figure isn't going to change so there's no need to do 1 and 2 again.

Now we'll go onto the black art of the damping adjustment.
If the bike feels unstable, loose and rather bouncy, then the rebound damping needs increasing. Just try a little at a time until you find the setting best for you. If the bike feels hard and bumpy, then reduce the rebound damping. Again, just adjust a little at a time. Make a note somewhere how much you've adjusted things.
If the bike has a tendency to bottom out under braking, then increase the front compression damping. If it feels too rigid or tends to hop under braking, then reduce the front compression damping. If the back of the bike bottoms out in depressions or feels unstable in fast corners, then increase the rear compression damping. If the back end feels rigid and harsh, then reduce the rear compression damping. Remember to make a note of all the adjustments you've made.

If it all goes wrong, return the bike to standard settings and start again.

hope this helps


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hi lilsilence, thank you for using fixya. below is a line from, answered the same question for a 2003 which is the intro for speed sensitive suspension.

Several ways to go here. Remove half of the fluid in each fork and addback a 10wt. This will approximate a 7.5wt. Going to a 10wt. willreduce bottoming but will give you some harshness. Depending on yourweight and riding style it is difficult to give you proper advice, justgeneralities.
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Draw out half of the fluid with a piece of tubing attached to a saryngeand put back an equal amount of 10wt. Adjust the level from there tosuit your comfort.
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1 Answer


front and rear. Panniers were full tankbag was full no topbox riding solo. THE BIKE originally shipped 20 weight oil for the forks. That was much to stiff for me. I talked with them and they suggested trying 15 weight and that 10 would probably be too soft. I tried the 15 weight and it was improved but still pretty harsh especially on small bumps. A friend with lots of experience related that he uses Silkolene 2.5 weight in his sport touring bikes (such as his Honda Hurricane and Ducati ST4). I installed 4 weight (actually aircraft hydraulic fluid, previously known to old Beemer riders as Aeroshell 4). I LOVE IT!! Compression damping is just fine. Rebound damping might be a tiny amount too little, but not enough to matter. Even dive under heavy braking is reasonable....much less than with the stock springs. ,It is difficult to get the right oil viscosity for everyone. Typically I ride 2up with wife, 400# plus gear, plus luggage, easily 440-450# total load. Even under those circunstances I may try W15 next time, but for sure not less. The Dutch WP is working with BMW, supplying the shocks and spring for the new K1200 S /R /PowerCup models. WP engineers (like Hyperpro) have designed a retrofit to the Front Springs for the Capo, as well as a rear shock. BTW, by coincidence those front springs are progressive too. They recommend from 5 to 20, depending on the typical bike loading. I suggest a look into the WP website, good stuff there. Here I am pasting some info from WP: ...the progressively wound Pro-Line front fork springs of WP Suspension play a fundamental role in the operation of your front fork. The springing and damping characteristics of your front fork can be fully optimised if the correct springs are used. Many motorcyclists know the problem of too soft front fork springs which can result in bottoming of the front fork when braking or too much movement and poor handling of the front fork during braking and acceleration. Original front fork springs can also be too hard which causes the front fork to shock the steering and the entire bike to feel uncomfortable on uneven road surfaces. With the WP Pro-Line front fork springs you are taking the first step towards optimum road holding at an attractive price. The springs, progressively wound from high-grade silicon chrome spring steel, ensure that your front fork will respond better (improved comfort), and react more controllable when compressed under braking (more stability, resulting in greater safety). In most cases motorcycle manufacturers use linear wound front fork springs which are often in the beginning but also at the end of the stroke, either to soft or to hard. Progressivity is lacking. With progressively wound WP springs you can solve this problem, once and for all. __________________ ,,,

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