well that's definitely a problem - wanted to be sure you weren't just seeing a little overflow from expansion.
If it were me - I'd clear out the radiator - blast it with a hose from behind.
pull the radiator hoses and blast the block out with a garden hose, see what kind of nastiness comes out - check the thermostat.
Been a while since I've touched one of those "newer" cubs - so can't remember too many details of them.
I assume it's got a water pump - be sure the belt's good.