KX Guru Racing

KX500 crank comparison 85-04
Here is the interchange info from Kawasaki.
85-86 KX500 - 86MM STD STROKE - 13031-1182
1987 - 86MM STD STROKE - 13031-1231
1988 – 86MM STD STROKE - 13031-1260
89-91 - 86MM STD STROKE – 13031-1285
92-04 - 86MM STD STROKE - 13031-1340

The crank bearings and seals are the same from 83-04.
The fly wheel taper and 12mm nuts are the same from 83-04.
The only differences I can find is the weight and the clutch side shaft.
The 85-87 used a key and a nut to hold the primary crank gear to the shaft.
88 and up used a snap ring to hold the primary crank gear to the shaft with no nut.
Kawasaki rods had different part numbers over the years but, the after market rods and rod kits are the same as well as the stroke at 86mm.
Here is a pic of the 85-86 kx500 clutch side of crank.
Here is a pic of the 1987 KX500 crank.
Here is a pic of the 1988 KX500 crank.

The pic below looks just like a 89-04 KX500 crank.
This pic is of a 1992-2004 KX500 crank.
Trying to determine the difference between the 89-91 and the 92-04.
I have heard that the 89-91 kx500 crank shaft is lighter then the 92-04.
But, that will require some verification.

From what I can see, 85-87 kx500 crank shafts look identical excluding the set backs which vary for crankcase volume.
From what I can see, 88 is the only kx500 crank shaft where it uses the snap ring on the primary crank gear but has the holes in the crank halves..
From what I can see, 89-04 crank shafts look identical.
So my best prognostication is that 85-04 can all be swapped as long as you have the correct primary crank gear asy to match the crank you are using.