kawasaki FD620 Fuel in Oil

[Old Goat]

Hey buddy, one old goat to another here, you mentioned going through the fuel system when you first acquired the machine.
Did you perhaps change the fuel pump? These are relatively low pressure pumps approx. 3 psi, if say a 6 psi pump is installed it will lift the float needle and permit excess fuel in the manifold which will richen up the fuel mixture. A rich fuel mixture is akin to driving around with the choke pulled on which could possibly foul the spark plug in one or both cylinders. RR

PS; just noticed you mentioned it is original fuel pump, oh well maybe previous owner changed it or the pressure relief failed, would not hurt to check fuel pressure at the carb just in case...

Well it certainly would not hurt to check it out. Can't say for sure it wasn't changed before I got it. Just assumed I guess it would not be an item that would be changed inside 82hrs.

[Motormanrod]

Hey! Not shure if you fixed the problem yet but i would replace the float valve in the carb and adj. The valves. If the plug looks oil fouled you may have blown a head gasket at the oil return port look for a bent push rod while the covers are off cause the valve guides walk from time to time.