Rear end feels vague with luggage and passenger

First thing I would do is make it boring: battery, grounds, loose plugs, obvious leaks. Boring checks save wallets. Ask me how I know.

I had something close to this and chased the dramatic answer first. It was not dramatic. It was a connector sitting half a millimetre out and laughing at me.

Can you reproduce it twice in a row? If yes, film the dash and note engine temp, road speed and whether lights/accessories are on. Future-you will thank present-you.

Thomas Spagnoli: a clean way to diagnose this

Good thread. This is the kind of fault that gets expensive when you start throwing parts at it because someone on the internet sounded confident after two coffees.

I would handle "Rear end feels vague with luggage and passenger" with a simple order of work:

1. Set preload for actual load and measure sag. Do this as a test, not as a guess. Write down what changes and what stays the same.
2. Adjust damping in small steps. Do this as a test, not as a guess. Write down what changes and what stays the same.
3. Check tire pressures cold and loaded. Do this as a test, not as a guess. Write down what changes and what stays the same.
4. Consider shock wear if adjustment no longer helps. Do this as a test, not as a guess. Write down what changes and what stays the same.

The important part is to change one thing at a time. If you tighten three connectors, swap a battery and clean two sensors in one afternoon, the bike may improve but you will not know what fixed it. That is fine in an emergency, terrible for learning.

Also remember the safety line: if the issue involves brakes, fuel smell, steering wobble, charging failure or a bike that cuts out in traffic, do not ride it like nothing happened. Test it carefully, or get it inspected.

I am Thomas Spagnoli, the professor who created the Motorcycle Mechanics Course. The course is free on this platform, and these exact habits are what I teach there: observe the symptom, split the system, test the basics, then repair. Enroll for free and use the lessons alongside the forum, because your bike deserves better than random part roulette.