KX Bottoming Help

[MikeKX250]

The bike is a 99 KX250, I weigh 205lbs. with my gear on. I ride mostly rocky, rooted woods with some occasional big jumping. I have all of the clickers set very stiff, but the bike still bottoms too easy and rides hard on the rocks since the adjustments are set so hard.
I went from a .41 progressive fork spring to a .43 straight rate. On the the shock I went from a 4.8 progressive spring to a 5.2 straight rate. How can I get more bottoming resistance without stiffing the ride and costing too much money? What is the cheapest way to get more bottoming resistance?

 

[marcusgunby]

You dont state if its your forks or shock or both.On the forks you can raise the oil level in 10mm increments, on the shock you can set the N2 pressure to 175psi and get a stiffer bump rubber.
Your setup is almost impossible to sort out as rocky rooted woods work requires a soft setup and then you go and do big jumps-you will have to decide which type of riding you do most and set the bike up for that.

 

[MikeKX250]

It`s mostly the rear that bottoms, will adding more nitrogen change the way the shock rides every where else too?

 

[marcusgunby]

The only thing to help on the rear without affecting the rest of the stroke is the stiffer bump rubber.Increasing N2 will help bottoming slightly and may also affect the smaller bumps but less so.Ive read woods riders are the hardest to cater for and i can see the problems you face.I think the only true was to fix it is to have 2 sets of suspension.Roots ,rocks etc requires very little damping to work well i would guess and then when you jump it bottoms hard.

 

[MikeKX250]

I`m not looking for an "XR" like ride over the rocks and have no bottoming while doing 10' jumps. I`m just looking for 1st more bottoming resistance 2nd a little softer over the small stuff. Right now I have all of my clickers set to almost the hardest settings so I don`t bottom as easy. There has to be some sort of happy medium, I know the bike won`t be super plush. How about the Race Tech gold valves would they help me?

 

[Hondaxrguy]

Mike, I'm curious how you are able to bottom your bike so easily. From your description, we are pretty much identical riders. I also ride mostly offroad, but do some MX for fun. Have you ever serviced the suspension? Are you running stock valving? With stock valving, my bike was acceptable on the rocks/roots, and great for MX. I've jumped 40+ft without bottoming either end. That was with the factory settings for everything. I've managed to bottom the forks once, with the clickers all the way out when I jumped, and landed the front end on the face of a whoop. I've never bottomed the shock. At least not hard enough to know it. It seems like something in there's not right.

Jeremy

 

[MikeKX250]

I replaced the piston in the shock last winter and along with changing the oil and recharging it. This helped with the bottoming a little but the back still seems to bottom too easy. Whenever I do a lot of jumping I find a lot of rubber on the rear fender.

 

[russ17]

It is my opinion like marcus said that you need to choose what you ride the most. If you want the optimul preformance out of your suspension.I to ride woods ect but accationally like to do a little mx from time to time.I have tried to get a happy medium between the too but it always seems that you suffer in one way or another in terms of control or handling. Also last winter seems a awful long time between service.

 

[DEANSFASTWAY]

Hi Mike From what Ive seen the KX 250 rear tire almost always rubs the fender . I too have set up a few of these KXs the same way (Springs any way) Mike ,When you say you replaced the shock piston did you replce with a std type piston or was it different flow or brand? Its real hard to find a good setup for those varying conditions we have in the east. I dont know about RI but in Jersey a typical Hare Scramble varies from bombed out crater sized 5th gear sand whoops to small rocks and tree roots in the woods .Its really hard to find a good Universal Combination that is effective everywhere Sometimes a compromise is made and riders opt for the softer plusher setup and some buy a cheaper steering dampener to help keep tracking straight in the real gnarlies . But your springs sound about right. Maybe just the setup Preload fork height oil levels etc needs some tweaking. Does your bike seem to ride level or is there more of a rearward basis ? I would also suspect that maybe you should check that shock out also maybe its blowing past the piston ring we almost always replace the o ring under the piston ring , They wear out quickly and beleive it or not they make a big difference . There are more expensive things you can do but I dont know your budget or intent for example you could try longer aftermarket bottoming cones for the forks There are also different pull rods for the shock linkage but I dont really think that is what youre after. Also sometimes the shock bumper can look fine but it is really worn out . As Marcus stated you could get a trick firmer one aftermarket that may help. Usually I like to set up a bike a bit firm and then turn out the clickers to soften up in the loose stuff but firm doesnt always mean real stiff springs. Keep us informed as wed all like to hear your resolution . GOOD LUCK

 

[MikeKX250]

It is the stock piston, I could live with setting it up stiff then backing off on the clickers to soften it up a little, as long as that wouldn`t make it bottom easy.

 

[marcusgunby]

Mike like others have said the KX will always leave a black mark on the fender-its the design of the bike.A fast local here used to leave a mark from the airbox to the tip of the mudguard, however he never felt it bottomed that hard.Go for the stiffer bump rubber and fresh 7.5 wt oil with N2 set to 175psi and then run the clickers alot further out.Dont forget the rebound will need to be set a bit faster as well due to the thicker oil.

 

[MikeKX250]

Thanks a lot guys. i know this has been covered before, but what do you think about using Mobil1 ATF in the shock?

 

[Rcannon]

Marcus, if you dont mind, I am not understanding how the higher N2 pressure helps with bottoming??? It just does not make any sence to me. Thanks!!!!

 

[marcusgunby]

Rcannon the higher N2 pressure will mean that the final pressure the shock is under(when compressed) will also be higher so adding to help the main spring.Its not really like spring preload in a fork im thinking, as that only really makes a difference on the first 1" or so of travel.
If you want to read up on pressures vs volumes do a search on google for boyles law-it states that if we decrease a volume by half we double the pressure.Do that help any?if not post back.

 

[Rcannon]

OK, I get it. I remember that law from my Physics class. It is funny how that stuff sounds so interesting...NOW. Not then. Thanks Marcus and everyone.

 

[MikeKX250]

What about using Mobil1 ATF for suspension fluid?

 

[Hondaxrguy]

Mike, many people are using it. Do a search and you should be able to find lots of info about it.

Jeremy