Aluminum shifter pedal upgrades, & larger splined shift selector shaft upgrades:
'93 & earlier KX125/250/500 shifters OEM and AS3 Performance or Apico (aftermarket cold forged shifters) are aluminum and a direct fit to the stock KDX shifter shaft's reduced spline diameter, as the KX shafts vs spline diameter are the same dimensionally.
You can't get a Hammerhead brand shifter specific to these '83(?)-'93 KX125-250-500 models, but a KX100/KX112 shifter will be exact fitment on the splines although I'm not certain the length will be the same, as they are for smaller riders. I personally didn't notice any difference in the length of the shifter while riding a 2022 KX112, which is an absolute missile of a mini professional motocross bike, fyi!
- Screenshot_20240624-104901.png (1.61 MiB) Viewed 16552 times
- Screenshot_20240624-104854~2.png (1.75 MiB) Viewed 16552 times
-------------------------------------------------------------------------------------------
If you want a larger diameter longer lasting spline for use with the larger diameter spline 1994+ softer (aluminum vs steel) shifter pedals, the shift shaft in the KDX200/220 engine has to be upgraded to the '94-'02 KX125 shift selector shaft with some light mods. Here's 2 bent small / reduced spline size stock KDX220 shift selector shafts, with a '94 & a '98 KX125 full spline size shift selector shafts:
- Screenshot_20240625-234722~2.png (3.58 MiB) Viewed 16462 times
'94+ KX125/250/500 2-stroke and KX250F '06-'18 shifter levers/pedals use full sized splines (same diameter as the rest of the shift shaft - unlike the reduced spline vs shaft diameter on the KDX and '93&earlier KX), and the KDX can be retrofit to a later (possibly as many different models as the 4 different KX125 part #'s '94-'02) KX125 shifter shaft, more details coming soon as I've just purchased a 1994-1995 version KX125 shift shaft.
Art Simmoneau has modified a 1999-2002 version to fit the KDX200/220. He uses the inner fork portion from the KDX shift shaft after removing it by grinding two wrench flats on the retainer/flanged portion of the pin's "head," grinding a pair of parallel wrench flats down to the pin diameter on the pin that retains this inner moving fork/pawl piece, and then grabs it with a wrench and rotates it 90 degrees (it's basically riveted in place on the welded on outer pawl/fork that's welded to the shaft) so that the inner fork/pawl piece will just slide off instead of being held captive. Then he grinds the other fork/pawl, the KX125 fork/pawl piece that's welded onto the end of the shift selector shaft, down slightly to match the profile of the KDX welded-on portion, then slides the KDX inner removable piece back onto the KX125 shaft, and rotates the riveted pin back 90 degrees so that the remaining portion of the flange retains the moveable piece again despite having two wrench flats ground onto it. Art then tack welds the back side of the riveted pin onto the welded-on fork/pawl piece just so that it won't rotate ever.
The EARLY-'94 version KX125 shift shafts (fits '94-'95 models) just have this riveted pin, but with no "head" on the pin to grind down and rotate parallel to the slot for removal, so this piece is able to be easily swapped out.
Also, I purchased the '94-'95 KX125 version (& a '98 on the way), in hopes that it or the 1996-1997 version may be directly swapable into the KDX engine, but have not yet verified. 1998 was a 1-year-only KX125 shifter shaft (looks almost identical to '99-'02), and 1999-2002 is the last one that's a possible option. 2003+ or 2004-2005 (2008 internationally before the end of the KX125 2-stroke) has a different design on the welded-on fork/pawl piece on the inner end of the shaft, so this is less suitable.
This comes from the factory with a round head, Art came up with the clever solution to grind wrench flats on this to be able to remove the KX125 fork/pawl and slip on the very slightly shorter KDX version, and then rotate the pin with the wrench flats 90 degrees so that it again acts as a retainer as it's designed, and then tack welding the riveted backside to keep it from being able to rotate out of it's now necessary orientation:
The inner portion of the welded on fork piece has a large ovalized slot (that a pin travels within) that needs to be ground out taller in order to facilitate the same amount of travel range as the KDX part that is welded to the KDX shaft. The length of the "ears" the welded on fork piece also need to be shortened up as you will see when holding it up to the KDX part that they protrude a millimeter or two further towards the front of the engine. Very basic grinding to adjust these.
- 309176212_10221498594469686_8618900838234012222_n~2.jpg (511.71 KiB) Viewed 16433 times
The 99-02 which Art used did require grinding wrench flats on the head of the pin in order to remove the forked piece that rotates on the shaft, in order to facilitate the grinding of the slot in the welded on portion larger than what it is to match the KDX part. I'll check the next time I'm in the shop to see if the earlier versions need this slot ground out taller or not.
KX250F 2006+ billet CNC'd Hammerhead shifter vs '94-'08 KX125/250 2-stroke forged aluminum Hammerhead shifter:
- Screenshot_20240626-095949~2.png (3.97 MiB) Viewed 16431 times
Art stated he prefers the KX250F version aluminum shifter, as it's slightly longer for his large boot size, and cam better accommodate a larger boot size 10 or 11 US and up, but also, Hammerhead sells replaceable offset shifter tips that are 10mm and 20mm further forward and swap directly onto their billet & their older forged shifters with removable pins (the "Moose Racing by Hammerhead" versions have a permanently riveted on tip). Art also stated that the KX250F shifters '06-'18 require a bit of grinding in order to seat properly on the splines, I thought he was saying they sit too close to the case, but now after receiving one I realized that the bolt threads are drilled in a slightly different (offset inboard) position which leaves these shifters 1mm more outboard so that they don't get full spline engagement unless you are to grind a little bit on the actual shift shaft where it is slotted for the bolts to slide through as a fail safe retention method, which is how you cannot pull the shifter off without completely removing the actual bolt so that if it comes slightly loose, so that it doesn't fall off on the trail. You wouldn't need to do the shaft 360°, only the portion where the bolt touches. I did consider perhaps just grinding the threads on the bolt itself closer to the head where it never has to thread into the other side of the pinch clamp portion of the shifter pedal. This would however allow the shifter to accidentally slide out a bit further if not fully tight, although even the stock shifter and KX shifter can move in and out a bit, so this should not be an issue.
*Avoid the cheaper Moose (my smaller '93& older KX Moose shifter isn't holding up so well in terms of spline wear), Tusk, and various "Amazon" and AliExpress brands, as these will surely be more likely to break off in a lay-down crash.
-------------------------------------------------------------------------------------------
