Head shake whilst under hard acceleration over a bump.
The stock SV does that as well. Go ride the A823 up to Knockhill here
http://maps.google.co.uk/maps?ie=UTF...,339.6,,0,6.57 and you are starting from slow speed as you cross the give way over the B914, then you are accelerating immediately into the first two bends, second bend is faster than the first one, so you can accelerate between the two, but it's on exit from these bends before you can properly get the hammer down. There are a few bumps and ripples in the tarmac as the road straightens out and climbs the hill. Under full throttle my SV would start shaking it's head as it straightened up, then get itself out of shape 2 or 3 times as it was under full throttle all the way up the hill. The bike was stock at that point other than a couple of teeth up on the rear sprocket.
As there is not a lot of weight on the front forks at this point, as the bike is trying to lift the front wheel, and squash the rear tyre into the tarmac, I always put that head shake down to the rear shock tying itself in knots.
Impossible for someone else to say without riding the bike, but from your description, is it not your rear shock adjustment you need to be looking at in this case? I'm no suspension expert, I can ride a bike and tell you what it feels like, but I can't necessarily tell you why that is.