I had this problem, remove hands from bars at low speeds and the bars would shake violently, thought it was due to topbox etc, turns out one fork leg was bent pretty bad,
Doesn't sound too promising if one had less oil than the other,
Their easy to remove and check-
Put on the centre stand and prop front up with a jack
Take off the brake calipers,
Remove front wheel
One side at a time loosen the lower yoke fork clamp bolt
Then the upper yoke fork clamp bolt whilst holding onto the fork
Slide down and out of yokes and see if their straight.
As others have said its not a good idea to mask a problem without knowing the reason for it!