I'm rebuilding my 02 cr250. I thought I'd replace the right side crank seal while I have her torn down. It was puking a lot of spooge and was using up some gear oil. My question is should I replace the collar as well as the seal? It looked like some oil was getting past the seal but I couldn't really find anything wrong other than the collar look like it might of had some wear. I couldn't find any specs on the I.D. of the collar. There are some wear lines from the oil seal. You can't feel them just see them.

Its usually the main bearing being loose and leting the crank wobble and suck in the oil. Check the main bearing for up and down play. There should be zero play.

I check that at the connecting rod and the crankshaft. I couldn't feel any play at all, they both felt tight.

im not sure about your bike, but mine i was able to just turn the collar around as it was symetrical. but if you cant feel any thing i wouldnt worry about it