Changes to make from progressive to straight??

KawieKX125

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#1
Well, after trying 2 sets of progressive springs in my 99KX125 and not being entirely satisfied because of harshness and bottoming, I found a stock set of springs from a 2001 KX125 to try. They are .41's in the front and a 4.8 in the rear. I am switching them out this week(Tomorrow) and I wanted to know what other changes I would have to make to the oil height and the preload to make them work properly? I am 140 without gear and ride supercross style tracks. I am a novice rider, but at this point with the stock springs from a 250, I bottom HARD over almost every jump with the clickers maxed. I need good bottoming resistence.

Right now I run 5wt bel ray fork oil at 90mm height with 7mm preload. Will this work properly with the new springs? Should I change oil height, weight, or preload?

I am rebuilding the shock too(for the second time). What oil weight should I use? Right now I am running Pro-Honda SS-7 5w oil. Should I go with stock N2 pressure or different?

Thanks for your help and once I get the bike dialed with these springs, it will be time to revalve myself(or mess it all up!). Also, are these springs the right rate for me? On the charts they look stiff, but after riding a 2001 KX, they seem fine for me.

Thanks again!:)
 

marcusgunby

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#2
kawi glad to hear your trying the straight rates.It sounds odd that you are bottoming so hard on your present set up as those 250 springs should stop that.yours is a 99 KX i seem to remember- i wonder if any wear is causing bottoming.wear will cause the oil to bypass the shock/fork pistons so they will not have the bottoming control they should.You can have wear on the shock body and shock piston ring.Make sure on shock/forks that the shims sit flat on the face of the pistons-surface them if not.On the forks ensure the midvalve shims are not warped(very common).Make sure the O ring on the base vave(fork) is in good condition as well.Look for wear on the midvalve piston ring as well.The springs should fit your weight for SX.I have 0.415 front 4.7 rear on my CR but i weigh more and dont ride SX(so it cancells out).I would start at the same proload/oil levels as too many changes are not good.You could try mobil 1 atf(slightly thicker than a 5wt) as it might suit you.On the shock i would run 175psi.Hope this helps and good luck.
 

KawieKX125

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#3
Good thinking Marcus!!! I never even thought of that. I might as well try them, then if it still bottoms, I will do all seals, etc. The odd thing is that whe the clickers are soft, the bike is AWESOME over bumps, it just bottoms over everything. It is also VERY hash on landings. Not plush at all. I will look into the stuff you mentioned when I tear it apart. Thanks for the advice!