Oil drain plug stuck

I just bought a 1975 KZ400 about 2 months back and right now I'm trying to change the oil on it, but there's a slight problem.....the drain plug is stripped. The bottom of the bike was extremely dirty, it looked like the dirt and grim had been collected over a long period of time, so I'm guessing that it's been a long time since it's had an oil change. I've tried spraying it with some PB Blaster and taking a pair of vice grips to it, but this sucker is on REALLY good!

Any advice?

The best tool to use would be a 6 point socket on a breaker bar if you haven't buggered up the plug with the vise grips. Even if you have though tapping the socket onto the plug with a hammer may actually help loosen it.
Once you get the socket and breaker on use a hammer and wack the handle of the breaker with a hammer, the jarring of the hammer will help loosen it better.
If worse comes to worse you could pull the pan and drill out the plug as big as you can without getting into the threads and use an easy out on it.
Good Luck

If you have rounded the plug too much you could try a big pipe wrench with an extensoin pipe on it for leverage and get an new plug.

I agree. A tight socket, long handle, tap with hammer.

If you rounded the head. there is nothing stopping you from filing the flats of the head until it fits the next smaller wrench (either metric or english) with a REALLY tight fit. I did that once.

And you're SURE that you aren't trying to TIGHTEN that bolt?
Being that it's up-side-down,it happens a lot!

Mine was stuck tight too... I finally got it loose by using a pipe wrench (stillson wrench) with a 2 foot breaker bar on the end.
As long as the threads aren't stripped, I can mill a new standard metric or english size hex on the old plug for you, send me a p.m.
Grant.