i had a bad shake on my 88" bitsa when i hit potholes/bumps in the road, i also had to slow down to a crawl to get it back under control, this fault was allowing both my front wheels to flap from left to right and back again rapidly continuously
my problem was a track rod end came loose in one of the drag links, the one from the steering box drop arm to the relay in the chassis member was the one that was at fault for me, this was pretty dangerous as if i hadn't have sorted it my steering would have come apart
mine was so violent that i couldn't control my steering wheel and was rather scary
get it sorted as soon as possible or you're likely to be crashing, ignore all these oil leaks as they're just a red herring in my opinion, sort them out after getting the steering safe
it's a two man job to check all the joints, one man in the cab waggling the steering wheel, you underneath feeling all the joints for movement that shouldn't be there
under no circumstances should you be driving this motor until you've found and rectified this problem