Swapping '03 KX 125/250 forks onto '00 KX 125

[KevinTwoStk]

The consensus seems to be that the '03 125/250 48mm forks are pretty good, and I have to imagine that they're better than the '00 125/250 46mm fork that is on my '00 KX 125.

The headset bearings are the same between the years, but I understand that the head tube on the '03 models was 6mm longer.

Furthermore, I know that the '02 KX models used the 48mm fork, but it's somehow different (right?) from the '03 fork. At the same time, the triple clamp offset for the '02 is probably a better match for my '00 frame than the triple clamp from the '03.

Long story short: I'm considering swapping an '03 fork onto my '00 bike by using the '02 triple clamps. Can anyone confirm that this will work?

[KevinTwoStk]

I've answered my own question.

I PM'd FlyinHawaiian, and he also seemed to think that '02 triple clamps would accept '03 fork legs.

Some Ebay shopping ensued.

Final combo:

--2000 KX125

--2002 125/250 triple clamps
--Azonic upper clamp for the '02
--2003 KX125 fork legs
--2000 front axle, wheel, and brake caliper
--2003 master cylinder

[KevinTwoStk]

And yes, the 2003 forks seem to be an improvement. The steering seems more responsive due to the larger-diameter fork legs, and the small-bump compliance is better. That's without any revalving other than what Pro Circuit already did for a previous owner. If I get them re-revalved for me I'm sure they'll be that much better.

[MXonaKawi]

Great read! i just picked up a used 2000 KX125 and I am doing a huge rebuild. I'm always interested to find out more about this bike and possible mods for it. The fork legs on mine are chipped in certain places and it bothers me so I've considered doing something similar. I'm guessing you would recommend it?

[KevinTwoStk]

Recommended? Yes. The '03 forks are 48mm and seem to enhance steering precision. It's not a night-and-day difference, though. I plan to get both ends of the suspension re-valved and it didn't make sense to put time and effort into the stock '00 fork when it wasn't all that expensive to swap in an '03 fork and go from there.

Some side notes on the '00 KX125:

--The stock rear spring is progressively wound, which has the effect of raising the spring rate as the shock gets deeper into its travel. That's fine, but when a progressively wound spring is coupled with a rising rate shock linkage, it results in a rear suspension that kicks instead of absorbs. I have gone to a straight-rate spring and have realized an immediate improvement.

--The stock front brake is mushy and weak. Pitifully weak! I swapped an '03 master cylinder onto my handlebar with good results. Braking power is much better, and the feel at the lever is firm and predictable. I'm still using the '00 caliper and rotor. 

--From what I've read, the '00 model had the best stock cylinder porting of the '99-'02 L-series KX125's. I can't comment on the other model years, but I can tell you I like the power delivery. I have a Pro Circuit pipe and an FMF TurbineCore 2 silencer/spark arrestor. Overall, it's a very linear power delivery with a bit of a hit in the upper midrange. Easy to ride. 

[KevinTwoStk]

Great read! i just picked up a used 2000 KX125 and I am doing a huge rebuild. I'm always interested to find out more about this bike and possible mods for it. The fork legs on mine are chipped in certain places and it bothers me so I've considered doing something similar. I'm guessing you would recommend it?

Minor damage doesn't always mean the parts have to be replaced. If the chrome on the lowers is nicked or gouged you can often somewhat smooth it out with a jeweler's file and fine-grit sandpaper--600 grit or so. The idea is to smooth out the damage so that the seal doesn't leak.

If your forks are dented or bent (upper or lower) then you definitely need to replace the dented/bent component.

[STM Suspension]

FWIW, I bought some 02 triples to go on my 07 because, in theory, they have less offset...  Yeah, theory is a nice place.

The 02 triples have the SAME offset as my 07, 25 mm.

And if someone really wants some 02 triples, I've got some at the shop...

[sandblaster]

Great read! i just picked up a used 2000 KX125 and I am doing a huge rebuild. I'm always interested to find out more about this bike and possible mods for it. The fork legs on mine are chipped in certain places and it bothers me so I've considered doing something similar. I'm guessing you would recommend it?

Minor damage doesn't always mean the parts have to be replaced. If the chrome on the lowers is nicked or gouged you can often somewhat smooth it out with a jeweler's file and fine-grit sandpaper--600 grit or so. The idea is to smooth out the damage so that the seal doesn't leak.

If your forks are dented or bent (upper or lower) then you definitely need to replace the dented/bent component.

Smaller defects and pin holes can also be tig welded and blended.

[MXonaKawi]

Great read! i just picked up a used 2000 KX125 and I am doing a huge rebuild. I'm always interested to find out more about this bike and possible mods for it. The fork legs on mine are chipped in certain places and it bothers me so I've considered doing something similar. I'm guessing you would recommend it?

Minor damage doesn't always mean the parts have to be replaced. If the chrome on the lowers is nicked or gouged you can often somewhat smooth it out with a jeweler's file and fine-grit sandpaper--600 grit or so. The idea is to smooth out the damage so that the seal doesn't leak.

If your forks are dented or bent (upper or lower) then you definitely need to replace the dented/bent component.

Smaller defects and pin holes can also be tig welded and blended.

My upper fork tubes have a couple of gashes in them that don't look too pretty. Previous owner didn't treat it too nice. I know...I'm a fickle bitch but I want it to look as close to brand new/perfect/works as possible. It's worth it to me. The inner fork tubes (chrome ones) are in great cosmetic condition. But the fork legs where the chrome inners are attached at the bottom, the dull grey metal part where the axle goes through have a few nicks and gashes. Good to know I can get them welded and blended to look new!

And thanks to your comments on my swingarm Sandblaster, I got that dent filled in with weld, smoothed and powder coated along with my frame. I will be starting a thread on my rebuild soon with pics. I'm picking up the powdercoated frame and swingarm today! So stoked!

[MXonaKawi]

FWIW, I bought some 02 triples to go on my 07 because, in theory, they have less offset...  Yeah, theory is a nice place.

The 02 triples have the SAME offset as my 07, 25 mm.

And if someone really wants some 02 triples, I've got some at the shop...

What condition are they in? And are they top and bottom 02' stock? How much would you be asking for them?

[MXonaKawi]

Recommended? Yes. The '03 forks are 48mm and seem to enhance steering precision. It's not a night-and-day difference, though. I plan to get both ends of the suspension re-valved and it didn't make sense to put time and effort into the stock '00 fork when it wasn't all that expensive to swap in an '03 fork and go from there.

Some side notes on the '00 KX125:

--The stock rear spring is progressively wound, which has the effect of raising the spring rate as the shock gets deeper into its travel. That's fine, but when a progressively wound spring is coupled with a rising rate shock linkage, it results in a rear suspension that kicks instead of absorbs. I have gone to a straight-rate spring and have realized an immediate improvement.

--The stock front brake is mushy and weak. Pitifully weak! I swapped an '03 master cylinder onto my handlebar with good results. Braking power is much better, and the feel at the lever is firm and predictable. I'm still using the '00 caliper and rotor. 

--From what I've read, the '00 model had the best stock cylinder porting of the '99-'02 L-series KX125's. I can't comment on the other model years, but I can tell you I like the power delivery. I have a Pro Circuit pipe and an FMF TurbineCore 2 silencer/spark arrestor. Overall, it's a very linear power delivery with a bit of a hit in the upper midrange. Easy to ride. 

Awesome info! Do you have a link to that type of rear shock spring? I'm not as savvy as you so some of that suspension stuff sounded like Chinese to me but I am eager to learn!

[KevinTwoStk]

One easy way to tell is to look at the spring and note the distance between each individual coil. Do this with the bike on the stand so that the rear suspension will be fully extended.

If the coils are closer together at one end (I'm talking about the individual windings) than they are at the other, you've got a progressively-wound spring.

If the spacing between each individual coil is uniform from the top of the spring to the bottom, you've got a straight-rate spring.

The two photos show my stock progressively-wound spring. I don't have any photos of my straight-rate spring yet, but I'm sure you get the idea.