Originally Posted by natedogg624
street engine into track bike, sure.
track engine into street bike, no.
This. Course, there's really no need for a motor swap at all unless the track motor is on it's way out... really all you need for the 06-07 motors is the keep the bearings fresh. Change them out somewhat regularly on a hard ridden track machine... Like yearly or so... I'm sure the street motor is in better shape, but you could always just swap track trim for street. Rather then dropping two motors and all that jazz... Unless of course, you've got track suspension and all...
In the end, it's really up to you. As long as the track bike is mantained well enough, there's really no need to replace it... Especially if it's practically stock. Now a fully built race motor is a different issue entirely... They are built to race, for a season or two... That's about it... the longevity of a fully built race motor is much shorter then a stock motor, which is more then capable as is for trackday junkies...