As mentioned, the 400 is fairly light as non-dirt bikes go at 366 lbs. Swapping out the exhaust and battery to after market ones can easily shed another 10 lbs.
BUT most of the weight that you feel is more a function of how you are holding the bike than anything. For instance, if you try moving the bike in neutral with it perfectly upright it will feel WAY lighter than if it is leaning off to one side as you instead of the tires are then holding up more of the weight. I ran into this recently when someone was helping unload my 400 from a hitch carrier. I was undoing the straps and they were like dang this is heavy. I looked, chuckled, and straightened the bike from it's tilt to one side. Then they said oh that's not bad at all. #physics
Another example is this middle aged lady lifting a much heavier Harley from the ground easily because she is using leverage and technique instead of just trying to muscle it.
Bikes are inherently stable in forward motion, which is why many drops happen at extremely low speeds. For instance, a new rider breaks too hard to a stop and throws themselves off balance. As the bike isn't moving it provides little resistance to the rider pulling on it right themselves and then the rider throws down an off balance foot and struggles to hold up the bike. This struggle has little to do with the bike weighting 340 vs 360 or even 450 lbs, but instead the fact that the rider is trying to catch themselves and the bike with an off balance, ill positioned foot. Yes as the bike tips farther and farther over the weight difference add up, but that's not the real reason you are falling over. In a normal stop on a heavier bike any person can (and often does) hold the bike up with one foot.
