I have a 1980 xj650, rode home after buying. It ran out of fuel, now i can not get it started. I've check plugs, spark, fuel flow to carbs, even changed the oil. The cylinders smell of gas and the plugs were wet. Any ideas are appreciated. Thank you.

It may be possible that when it ran out of fuel that it grabbed any **** that was in the bottom of the tank and put it into the carbs, which may have gunked them up and they might need to be cleaned.

To verify that it IS or is NOT fuel or Carb related, get some starting fluid and shoot it into the air filter box ( or along the pod filters if the original box has been removed) to see if it starts. If it DOES start, you have a fuel issue either with the carbs being gunked up (idle jet or main jets), or the floats could be stuck open (again with gunk from the bottom of the tank) and thus flooding out your motor (you said it smells like gas). Usually if it smells like gas and the plugs are wet, something is wrong with the ignition since its not burning it. So if all of the above is OK, check the timing under the points cover, you may have to set the gap (on most older bikes its around .30-.40mm) But since you rode it home I doubt thats it.