From the looks of it, your caster is out, looks to be in the 2-3 degree range. That'll do it, then add no sway bar which'll add to the body roll while trying to keep it straight. while you're at it and check your Toe in as well, if that way out it'll get ... well ... lets say a 'little' squirrely at speed.
If you have adjustable arms, either shorten the uppers, or lengthen the lowers to bring the caster back to 4-6 degrees (I'm at 5-ish and she's a lot more stable than my first test run at 2 degrees ... which was a two fisted, full strength, hell ride I never want to redo). You want to roll the axle forward on it's axis a little.