You need a lever from a 1989 KX125. It will mount on to the existing boss. The oem lever can only be bought complete with its KX boss for around $100. There should be an article on it here justkdx.dirtrider.net
ok any 98 to 02 kx lower knuckle will work, if you have a hybrid in a kx frame before 03 you can either use the 250 kx top lever for more length or the kx 125 lever 96 to 06 for the shorter version, 03 and later frames you will be suited for the 02 and back lower knuckle and the 03 and newer top half do to its shape it fits the frame better, however on either the nut which holds the lever on needs to be drilled slightly to countersink it as the 250 lower knuckle is just a shade narrower.
I did the mod with a KX125 starter off **bay. Must use KDX knuckle, and I had to file the KX lever a bit for clearence. I was happy, BUT....the shorted lever slams my arch into the footpeg. I've tried to "learn" a new kick, but after hurting my foot, I went back to stock. Just be aware!
After all the effort I put into fabricating a hybrid kick starter I am back to OEM. I scored a cheap used OEM kdx kicker on *bay. It came together with the knuckle, but like all old kickers it was very sloppy. Once they get sloppy, they tend to bend the washer and circlip that keep the pedal from slipping off the knuckle. I put a brand new washer and circlip, and within 3 kicks they were bent again. So I tossed them in the trash and got a big fat washer at the hardware store. It is about 5mm thick and its I.D. is just slightly bigger than the knuckle post. Top of this fatty is flush with the top of the post, which is where I welded this puppy. It ain't coming off now! While I was in there, I put a blob of weld on the contact surfaces between kicker and knuckle 'cuz it was badly worn. Then 5 minutes with a file to shape the blob into a flat contact surface.
IMHO the OEM kicker is much more comfortable to use, and doesn't destroy my boot. It is still a sloppy fit on the post, but who cares!
I still have a new Fredette kick start lever, and now my wife will NEVER use it because she sold her KDX, and went over to the Orange side. I need to look at it closely, cuz if it will work on my orange 300 bike, I might just try that.....but then, I've yet to use the kicker to start my three hunny.