My Roadglide wobbled like that at 40mpg on deceleration. It was a “head bolt adjustment”. This phenomenon began after a dealership dropped the bike off of a lift. You can only tighten the head bolt so tight and as it tightens the bike will have trouble leaning over into a turn and then dive. Thankfully my challenger does not act this way.
The death wobble is not the same problem. The death wobble is in the rear end. This is called a tank slapper and is caused by an under inflated front tire or a loose steering head nut or bad bearing.
