Super stiff suspension and lowering

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4/14/2018 12:14 PM
Edited Date/Time: 4/14/2018 12:15 PM

I recently purchased a used 2009 Kx250f that the previously owner installed full SFF air Tac suspension and shock from a 2016 kx450f. There are a couple things...the bike is a little tall for me by a couple of inches even after I shaved the seat down and the other thing is the suspension is very stiff and not plush at all....I am thinking of converting to traditional spring forks for a plusher ride...I have messed with the air in the suspension and nothing seems to help. My sag is set at 101 and the static sag is 35. I weigh 190 lbs with street clothes on. Would anyone suggest lowering the bike for the height challenges? Any suggestions and opinions welcome?


4/14/2018 10:26 PM

Lowering links make the initial stroke of the shock stiffer. Try one and back the compression out a bit. If heights an issue then id say go for it. A lot of people get lowering links to work for them.


4/15/2018 9:37 AM

The best way to lower the bike is to have spacers put in the shock and forks, limiting how far they will extend. Of course this involves taking them apart, but just lowering one end of the bike will have negative effects on the bike's handling.


4/16/2018 12:15 PM
Edited Date/Time: 4/16/2018 12:19 PM

You said you messed with air pressures in the fork. So what have you tried?

Even though the forks are designed for a 450 and you have them on a 250f, given your weight i'd suggest starting with the stock recommended air pressure settings for the 16 KX450f:

Inner chamber : 165psi
Outer chamber : 14.5psi
Balance (bottom) chamber : 175 psi.

Make sure you are setting the pressure with the front wheel off the ground, and follow this procedure:
1. Let air out of the balance chamber
2. Let air out of the outer chamber
3. Set the inner chamber pressure
4. Set the outer chamber pressure
5. Set the balance chamber pressure.

If you feel that the initial part of the stroke is too stiff, try:
1. Lowering the outer chamber pressure 3-5 psi.
2. Raising the balance chamber pressure 5-10psi.

Also, dont forget that you have compression and rebound damping clickers on the left fork leg to use. Most people get too caught up on messing with air pressure and don't even touch the clickers. My suggestion is to start with the stock 16' KX450 air settings, and work with the compression and rebound clickers to get the feel you want. Start with the clickers in the middle of the range (12 out) and work from there, making 2 click adjustments at a time. If you still feel the fork is too stiff, then make slight air pressure adjustments to soften the initial part of the stroke up (add a few psi to balance chamber).


4/16/2018 7:12 PM

By the way. If you are thinking about getting rid of those air forks, please let me know. If they are in great shape i may be interested. Looking for a set to put on my KX125.


4/17/2018 12:34 PM

I am thinking about switching to traditional spring setup. These forks and the shock are in immaculate condition with only about 20 hours on the entire setup. Let me know and maybe we can work something out $$$.


4/19/2018 6:13 AM

I have the same problem. I have a 15 kx450 and i cannot get the forks to move. Ive talked to alot of suspension companies and they all say you have to revalve. This doesn't make sense to me due to lack of movement in the first inch of travel. Has anyone tried playing with the shim stacks themselves?