Just went to look at a 1999 Yamaha XL700 . Everything seems ok, 146/152psi on the compression test. Only thing that bothers me is a little two stroke oil in the bottom of the hull. All lines to the oil pump look good and in tact. Anything to be worried about?
You probably have a leaky oil tank or simply overfilled at some point and never cleaned the bilge. you can premix it if you have a concern! you can also leave the oil pump hooked when you premix it! really!