it's possible but not totally straightforward. here are some top tips from greasy125:
greasy125 wrote:
you'll need a complete ET4 wiring harness. you'll also need the ET4 gauge panel, the CDI and antenna.
the ET4 and ET2 have different brake lever perches for the rear brake, and the rear brake cable is different, too.
you'll also need the battery tray and relays for the ET4.
i think that the front shock is different too.
the battery cover rear seat latch is different between the 2 and 4 as well.
while the 4 motor will bolt right up, the swing arm is different. i think that the 4 is a little more robust design.
and finally, you'll need the ET4 key set, too.
oh and all the stupid little clips and clamps and such that are different...
all in all not an impossible feat, but it's quite time consuming. i did the boogie using a pretty complete ET2 minus the motor and a wrecked ET4 and it took me two pretty big evenings.