my 4k ke70 had same problem, a month later block filled with coolant, my head gasket was slowly going, have you done a compression test?
get ya carby rebuilt would be the go, you can do it yourself and it will cost you not lots, i got my stock carby rebuilt and it cost $300! bastards, anyway now I'm getting rid of that one for a nikki carby.
Hope it helps man
o and check for bubbles in your radiator, if their is some you got blown head gasket.
Travis