The photo at the left shows a comparison of two versions of KYB fork tubes found on Yamaha YZ and YZ-F motorcycles.  On the left, the early design tapers out to 55.6mm for the upper triple clamp while the later design has no abrupt taper and measures 53.6mm diameter.  As indicated by the red arrow in the second photo, the flange on the 53.6mm diameter fork cap matches the diameter of the WP fork tube.

KYB cartridges from 53.6mm diameter applications can be used with WP fork tubes directly without any modifications.  KYB cartridges from 55.6mm diameter applications must have the flange turned down using a lathe so that the caps will fit through the KTM/GasGas/Husqvarna triple clamp.  A final diameter of 2.110" to 2.120 (53.6mm to 53.8mm) should be your target. 
If your fork cartridge caps are 55.6mm to 55.8mm diameter and you have purchased a conversion kit from Dialed Manufacturing, we can turn your caps down to fit your bike free of charge.  You'll have to cover the shipping cost.  Please clean and dry all parts, then contact [email protected] for more information.

When measured as shown, a 2009 YZ450F fork assembly is a good example of the shorter Yamaha KYB Cartridge application.  A rough measurement of 37-7/8" (962mm) to the bottom of the fork lug (or the rebound clicker) can be used to identify short Yamaha KYB forks.

A 2012 Kawasaki KX450F cartridge in combination with WP21KKIT-L is a direct fit into a 2023 GasGas MC350F or KTM 350SXF.  The same is true with any 2014 or later Yamaha YZ450F or YZ250F cartridge.  Rockstar Husqvarna models are also good candidates for these combinations.  Measured the same way as the short KYB fork above, this long KYB is very roughly 38-5/16" (973mm).

     There are at least two different length versions of the KYB SSS/AOSS cartridge which differ by approximately 10mm at full extension.  It is important to choose the correct conversion kit to match the fork cartridges you want to install in your KTM, GasGas or Husqvarna motorcycle.  Motorcycle applications with KYB forks are listed below, sorted into two cartridge lengths.

KYB cartridge applications with lengths we have not measured:

• 2006 - 2007 YZ125, YZ250, YZ250F, YZ450F  (a customer stated that these are longer tubes)
• 2010 - 2011 YZ250F
  
• 2012 - 2013 YZ250F

     To complicate the matter, standard Husqvarna motocross models from 2021 onward have a 10mm lower ride height than their KTM and GasGas equivalent.  This means that the upper fork tubes are 10mm shorter.  This does not apply to Husqvarna "Rockstar Edition" models.  Your fork tube length can be confirmed by measuring the length of the upper fork tube and referencing the table below, or checking the OEM parts diagrams.

     The two conversion kits available from Dialed Manufacturing differ by 10mm in length.  The kit for long KYB cartridges (WP21KKIT-L) is the primary product for all Austrian bikes and it is the easiest route that most customers should choose. 

The intent of the kit for short KYB cartridges (WP21KKIT-S) is to provide customers with the option to use the cartridges from older Yamaha four strokes and all Yamaha two strokes.  These shorter cartridges are often less expensive as old bikes are parted out.

It is important to note that we have not measured or tested every combination of parts, but have sampled and cross-referenced to come up with what we believe to be accurate information. Some blind-spots are the early Yamaha and Kawasaki 48mm SSS / AOSS fork cartridges:

• We have hands on experience with 2008 later Yamaha as well as 2009 through 2012 Kawasaki KYB forks.
  
• We have not confirmed if the WP fork lugs used on Austrian off-road models with spring forks are compatible with our kits.  Our kits are designed specifically for the 2021 and later models with XACT air forks.
  

Dialed Manufacturing conversion kits are designed to work with the springs from the motorcycle application you sourced cartridges from. 

This means, if you buy a complete set of donor forks, you can use the OEM springs from that fork and the cartridges together for your conversion.  If you buy the springs separately, buy springs to fit the make, model & year your KYB cartridges came from.

Some aftermarket springs from vendors like RaceTech are slightly shorter than OEM springs.  They require spacers or shims to set the proper preload.
If you use aftermarket springs, please follow up with the vendor for correct fitment.  It will be identical to assembling a KYB fork.

Some standard spring lengths are listed below.  Aftermarket springs may be up to 5mm shorter to allow zero preload.

• 2008 - 2021 YZ125 & YZ250             (454mm springs)
• 2014 - 2024 YZ250F and YZ450F   (497mm springs)
• 2010 - 2013 YZ450F                           (470mm springs)
• 2007 - 2012 KX450F                          (470mm springs)
• 2009 - 2012 CRF450R                       (460mm springs)