I just did the top end on a 1980 KX 125 I recently purchased. It ran when I bought it and it smoked but at the time I figured it was just because it hadn't been run for awhile and I didn't run it very long. I probably should have. To make a long story longer the bike runs good but the smoking does not really go away or lessen. Could this be a bad crank seal and if so can it be replaced without splitting the cases ? Google searches don't show a whole lot on this subject for this model.