Re: Small.. 1993 Cbr f2 problems?
I would check compression in those 2, actually if you're testing just test all four. Blade is right, white is usually coolant, how fast are they fouling? Are you leaking any fluids? Is there coolant in your oil? If there is coolant in your oil and you have bad or stuck rings the oil can slip past the piston and foul out the plugs, if there is coolant in the oil and it slips by the rings there will be a milky/crusty build up on your plugs and it will happen pretty fast, depending on how bad the rings are.
White - coolant
Black - brown and usually wet is oil. Either one is not good, but it happens.