Assuming the engine ticks all the boxes, turn to the chassis. Does the steering pull to one side? If you take your hands off the bars, does it start weaving? How are the brakes? Does the suspension feel plush and controlled, or is the bike bouncing about over bumps and ruts? Are there any thuds when you brake (loose steering head bearings can cause this)?
Flag up anything unusual in your mind – it might help to stop halfway and take some notes on your phone or a notebook. Then, when you get back, go through your list of queries with the owner to see if they have any explanations. Then you can take a view on whether you want to haggle a discount based on what you've found, whether you're going to walk away, or if you're happy with what you've seen and ready to buy.
- Find the ad for the Kawasaki Z650 pictured above here.