My bike is one of the type that has a grease nipple on the steering head and it gets a couple of squirts with the grease gun each service.
Recently I thought I had a leaky fork seal, again.
A bloke told me that it was not fork oil on my fork. He reckoned that on hot days the grease in the steering head bearings sort of liquifies then runs down the lower triple tree and since the sidestand is on the lefthand side ends up on the left fork tube.
I guess it sort of sounds feasable however steering head bearings don't get very hot.
Wondering if anyone else has had this?.

have a look where the dust cover on the fork is.

usually if a seal is leaking the dust cover will be moist and might have a buildup of dust & crud around it plus a leaky seal will usually also run down the lower fork

Do you get the oil on your knees / pants after riding? that is usually a good indicator of a seal gone bad (thats what mine was doing!)

No Rob, the obvious signs are/were not there.

To anyone lucky enough to have a grease nipple on their head stem, grease it yourself. Make sure you keep pumping untill you witness grease exiting from the ends, then clean off any surplus. Only then you can give a couple of shots every year or so depending on the amount you travel.  Harley are notorious for only using the minimum amount in these bearings and i was surprised how many pumps it took the first time i filled it. ( shitloads) 

I was told by a local Harley mechanic that he has seen many new bikes on days of old that had never had the stem area filled right from new.