All two strokes throw a bit of oil down the exhaust, so if you pipe top barrel joint is poor it will leak out. This is normal. By all means check the oil pump adjustment, it may be over adjusted by a previous owner thinking more oil the better. ITS NOT. Look in the workshop section I'm sure its all in there.
Also remove the oil pump, and check that the driven shaft oil seal is not sliding down out of the pump body. This lets two stroke oil leak into the gear box.
Years ago i found out the hard way that cheap oil is a false economy. Oil is a lot cheaper that top end rebuilds. I ran an LC on some Fina crap the rep gave me. It was fine in the old air cooled 250, but the LC seized twice before i changed to Motul synthetic. Never seized again!