My Yamaha Yzf 600 '97 motorcycle just broke down?

[Saverain]

I was driving it on the highway, kind of pushing it and black smoke started coming out of the exhaust, may for about 5 minutes. I pulled over and everytime I tryed started it it would smoke and then shut down. I left it on the side of the road and had someone pick it up. I haven't looked at it since, but what oculd be going on? I just put in a quart of oil and there was engine coolant in there and it didn't go past 100 degrees on the temperature guage, I put on the fan while riding because it was getting there, maybe I shouldn't of. What should I do to get it back up running?

[emucompboy]

Check the oil level and make sure it's between the two lines. Too much oil is bad.
You're going to have to clean your spark plugs.

[guardrailjim]

Possible blown head gasket - coolant leaking into the cylinder would blow smoke out of the exhaust pipe.
The coolant could seep past the rings and down into the crankcase.
Coolant isn't combustable, so that would cause the no start symptom.
Pressure test the radiator to check for a head gasket leak.