Heads up on new KX forks

marcusgunby · Dec 16, 2002

I stripped the KXs KYBs and to my horror found swarf and rust in the base valves-this bike hasnt been ridden, the base valve have been sitting in the oil-how do the shims get rust on them-who knows??

steve125 · Dec 16, 2002

Marcus I assume swarf is muck, grunge or crap? Yes! I bet that is real common even in new forks if moisture is present.

bclapham · Dec 16, 2002

steve, where i came from in the UK, swarf usually meant bits of metal left behind during the machining process. who knows what it means in Leicestershire though, the people accross that way were always a bit weird, although they did used to roll into our town once in a while for some good fights!

russ17 · Dec 16, 2002

carefull! Not much thread on the midvalve post either to boot its a coarse thread.

marcusgunby · Dec 16, 2002

russ i have done one midvalve previously on a KX 03-you are right the nut has little spare threads and needs careful work.Notice it has a 2 stage midvalve and a single stage base valve-different.

russ17 · Dec 16, 2002

Yeap! I thought it was a kind of a cool arrangement.

Eddy V · Dec 17, 2002

Marcus,
Do you have already some advice for improving the forks if this is necessary because we have only done the break-in and are now blueprinting the engine.We have some problems with truing the crankshaft.It's 0.2mm out of balans and very difficult to move.

dbrace · Dec 17, 2002

ive seen heaps of fork springs and damper rods especially, with rust on them (say goodbye to your cartridge bushing). makes u realize just how important that first fork and shock service is.

DEANSFASTWAY · Dec 17, 2002

Did a set of 03 YZ250 forks and thecartridge rod was all pitted up but there was no real evidence of water in the oil. Springs were rusty too . Iguess if theres real water content in there it will sink to the bottom like at the B/V but if its like misty it will stay up top.

Bud-Man · Dec 17, 2002

The water most likely came from the moisture in the air. Hot-cold cycles will cause condensation and the water drops will cause corrosion. If they fall into the oil then they will sink to the bottom and likely settle on the base valve as water is heavier than oil. Seems like the corrosion is more common on bikes that sit a lot or are stored. I'm guessing that it's because the bikes that are ridden get oil splashed all over the fork internal frequently enough to protect them. Things get a lot worse when you put a pressure washer into the picture as it's easy to blast water past the seals.

Marcus, what did you mean by swarf? Was it dirt or metal pieces. If it was little metal shavings then it was likely a poor job of de-burring or cleaning at the factory. (I'm noticing a lot more of this in other things besides motorcycles these days.)

marcusgunby · Dec 17, 2002

Eric it makes ence what you say about the water going to the bottom of the fork. The swarf was little metal slivers-it maybe from the cartridge turning as i tried to spin the base valve out(good thread lock on them) but since some of them were actually in the base valve i think its from the factory.
I was horrified to find more bad stuff in there than on much older forks.

marcusgunby · Dec 17, 2002

Eddy V i have been experimenting with 2 different setups-one uses a standard midvalve and softer base valve with a higher oilo height to prevent bottoming(100mm airgap) the other is totally different to std, it uses a singel stage midvalve with alot less lift and a much softer base valve with std airgap.Havnt had a chance to test them as it just keeps raining all the time:(

holeshot · Dec 17, 2002

I've taken one fork on my '03 KX125 apart to replace a seal, and removed the cartridge rod and base valve (I found out late that you don't need to remove those parts to replace a seal). Aaaargh. I made a cartridge rod holder from PVC pipe (per Motoman 393's site) and everything came apart clean and easy. I'm not having any problems with the forks, so I didn't feel the need to investigate further (and I wasn't too sure as to what I was looking at anyway).

dbrace · Dec 19, 2002

please let us know your results marcusgunby im keen to learn. btw its sunny here in brisbane australia but then again the tracks r waaaaay to hard and dusty. cheers.

marcusgunby · Dec 29, 2002

Well i got some testing in at last-a bit of a surprise really, the 2 different setups didnt feel as different as i would expect-both were plush and resisted bottoming well-the more modified fork(single stage midvalve)was slightly plusher on smaller ripple bumps(it also has a much softer base valve) however the 2nd fork hasnt really bedded in so may improve in this area.In future im thinking of just modifying the base valves on this fork as it takes a bit less time(and shims) and the performance isnt much different.

On the shock i have gone more radical-ive had to drop the std 4.9 and goto a 4.4 spring-ive reduced LSC and used a smaller claming shim-its worrying how far ive had to go (softest stack i have ever used in a KYB) but the results are good-nice plush ride-no kicking under breaking and hardly any bottoming even in the think mud i was riding.I think the KX linkage must be very progressive.

Mattski · Dec 29, 2002

what do you mean by a smaller clamping shim?(shock)
Is this the smallest shim on the stack?
did you decrease its diameter or its thickness?

marcusgunby · Dec 29, 2002

Yes the clamping shim is the smallest-it sets up the whole stacks strength so if you looking to get rid of a big amount of damping the clampshim is the obvious choice-its the diameter you alter as its thickness doesnt matter as it sits up against the plate so it doesnt flex.

holeshot · Dec 29, 2002

Originally posted by marcusgunby

I think the KX linkage must be very progressive.

This is my impression also. It seems to move easily through the first half of it's travel and then quickly becomes real stiff, giving the impression that it's bottoming. I need to work this out before I do anything else (or should I say Marcus will work it out). I've never had a rear shock apart, so I will have to bring it to a suspension shop (RG3 probably).

Mattski · Dec 30, 2002

Does this mean that if you were to remove the smallest shim in the stack that the dampening would decrease over the whole range, and if you were to do the opposite and add a smaller shim (if possible) that this would increase the dampening?
What can be done if a smaller shim can not be fittedto the bottom of the stack?

marcusgunby · Dec 30, 2002

Ive heard only good things about RG3 so i think you will be in good hands.

 

I forgot to say i did a good experiment with the shock on the KX-2 different bikes

one with a softer spring and stiffer damping(mine)-the other stiffer spring softer damping(daves)-mine was a better combination-the stiffer setup wallowed slightly and didnt feel as planted and despite the stiffer spring it bottomed easier.

Eric82930 · Dec 30, 2002

Matski
You have it backwards. If you remove the smallest shim then the stack will sit on the bigger shim above it which will make an overall increase in damping force because the whole stack has to bend around a bigger shim.

Eddy V · Jan 3, 2003

Marcus,
Can you give us some values of the shims you use in your modified stack in your kx shock?

russ17 · Jan 21, 2003

Originally posted by marcusgunby
Well i got some testing in at last-a bit of a surprise really, the 2 different setups didnt feel as different as i would expect-both were plush and resisted bottoming well-the more modified fork(single stage midvalve)was slightly plusher on smaller ripple bumps(it also has a much softer base valve) however the 2nd fork hasnt really bedded in so may improve in this area.In future im thinking of just modifying the base valves on this fork as it takes a bit less time(and shims) and the performance isnt much different.

On the shock i have gone more radical-ive had to drop the std 4.9 and goto a 4.4 spring-ive reduced LSC and used a smaller claming shim-its worrying how far ive had to go (softest stack i have ever used in a KYB) but the results are good-nice plush ride-no kicking under breaking and hardly any bottoming even in the think mud i was riding.I think the KX linkage must be very progressive.

russ17 · Jan 21, 2003

Well marcus ! did that second set of forks eventually bed in. I was going through some old post. Just wondering.Man I still can't get this quote thing down.

russ

marcusgunby · Jan 21, 2003

Russ this is hard to beleive but i havnt rode it since-weather has been crap, bike is at karl prestwoods having a pipe made-should have dynos by the end of the week.

Heads up on new KX forks

marcusgunby

steve125

bclapham

russ17

marcusgunby

russ17

Eddy V

dbrace

DEANSFASTWAY

Bud-Man

marcusgunby

marcusgunby

holeshot

Crazy Russian

dbrace

marcusgunby

Mattski

marcusgunby

holeshot

Crazy Russian

Mattski

marcusgunby

Eric82930

Eddy V

russ17

russ17

marcusgunby

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