ec300 06 front sprocket loose on countershaft splines

[hillbilly]

Anyone had problems with excessive wear of splines on countershaft where sprocket fits. Just rebuilt engine, (failed main bearings) and when fitting new sprocket noticed there seems to be a lot of slack between two components. Dont really want to tear down engine again to fit new shaft. Had an 03 450 a couple of years back and that had same issue, might expect it for older bike but this 06 not done much work. Laid up 2 years and trail ridiing only befoe I go it. Any ideas? Maybe thats how they are? Tried 2 new sprockets and both same, visually splines don't look worn either.
Any info appreciated