If the oil in the rest of the lubrication system looks OK and isn't milky (and the coolant is OK) then it's probably more than likely it is just normal condensation collecting inside the cap as it is a cold spot. You'd expect to see this sort of cold spot milkiness generally on a motor that was/is run on lots of short journeys or in winter time. Is it running OK?

I've just read your posts in the Ask Kev section... obviously your bike isn't running OK! Time to investigate I would suggest?

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