Suspension Tuning ?'s

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govols
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Suspension Tuning ?'s

Post by govols »

'05 kdx 220...rides pretty stiff. My rear shock had lots of preload. I reduced it to almost no preload. Back end is still stiff. Front end is just plain stiff after the initial 3" of travel. I weigh 148. I don't know where to begin because I know little to nothing on suspension tuning. I do have the "tech-spark" online service manual. All suggestions welcome. Thanks.
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Re: Suspension Tuning ?'s

Post by KDXGarage »

Are you the original owner?

Do you know if it still has the original springs?

How long has it been since you cleaned, inspected and lubricated the swingarm and linkage bearings?

How long has it been since you last changed the fork oil / shock oil?

Do you weigh 148 or do you weigh 148 in full riding gear?
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govols
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Re: Suspension Tuning ?'s

Post by govols »

No, third owner.
No idea if it has original springs. How would I check?
Just bought it and am refreshing top end now and have not inspected or lubricated any linkage bearings
Will be changing fork oil soon. Not sure about how to change shock oil
148 with street clothes
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bufftester
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Re: Suspension Tuning ?'s

Post by bufftester »

In stock trim the KDX is sprung for a 180lb guy in the rear, and a 130lb guy in the front (sounds like the description of one of my ex gf's :oops: ). You already have the top end out, no better time to go through your bearings, linkages and suspension. the linkage is the most abused/ignored part of the bike (ask ICRage http://kdxrider.net/forums/viewtopic.php?f=77&t=13644). Likely you need to replace fork seals anyways. Unfortunately no definitive way to tell what springs are in there. Best ballpark is to measure your static/race sags...that will at least let you know if you need to go up or down a spring (http://kdxrider.net/forums/viewtopic.php?f=102&t=1110 and http://kdxrider.net/forums/viewtopic.php?f=102&t=1109). I have the stock ones from my 2001 220 that you are welcome to have. If there are heavier ones in yours it will at least soften the front. Shock oil isn't too difficult.
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Re: Suspension Tuning ?'s

Post by KDXGarage »

Thank you for the reply. I suggest you check the swingarm and linkage bearings first.

Is there a color dot on the spring? If it was 2004 and earlier, I would just say stock is sky blue, but I think 2005 and 2006 were gray. KYB uses paint codes on MX shock springs, but I am not sure about the KDX ones.
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Re: Suspension Tuning ?'s

Post by gsa102 »

After cleaning and greasing the linkage bearings, check the sag on the rear end. You adjust the spring tension by screwing the nut on the spring in or out to get the rear to sag 100 mm with you on it. If the spring is too light or too heavy for your weight it will end up stiff when you adjust the tension to compensate.

After you set the rider sag, measure how much the bike sags under its own weight. You should be 25-30 mm if you have the right spring. You adjust the rest by the clickers on the top (compression) and bottom (rebound) of the shock. Set the rebound first because it also affects the compression. For the rebound, you want it as loose (fast) as you can get without feeling like the bike wants to kick you over the bars. The compression makes it feel soft or stiff.

Forks - put a ziptie on a fork tube and ride hard and fast. You should be using most of the travel if you are close to the correct spring rate in the front. It's easy to change the fork oil, take off the top cap, take the spring out, and dump it out. Put fresh oil in and pump it a few times to get air out, measure from the top lip with the fork compressed to set the oil level. Put spring back in and reassemble. You can vary oil weights and oil levels to adjust how the fork works. Also bleed the air out before you ride by the little screw on the cap.
This is my rifle, this is my gun, the YZ to go fast, the KDX is for fun!

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