I always look for:
- Are the covers ragged out? Like barely any paint, big gouges, decent sized dents? Are they aftermarket or recently replaced? Small normal wear is fine.
- Bolts being mismatched is a good one. I dont mind hardware store bolts on say a small cover like for a powervalve but bolts for case halves, clutch, ignition cover watch for. Also cylinder head bolts and such are ones to look for as well.
- Chain, guides, rollers. Drive system overall. Is it ragged out? Chain worn badly? Sloppy? Sprockets look trashed? Rotors also falls into this caregory.
- Plastics. Do they look like they got slid down a mountain full of rocks? Minor scratches and tiny cracks I wouldnt worry about.
- Wheels. Take a stand with you. And roll the wheels. Look for warping side to side or dents, cracks. Loose spokes? Check for bearing slop as well.
- Check the frame over for cracks as well or any good dents. If it has a skidplate, TAKE IT OFF, and look under it. Also look for any welds or paint corrections.
- Suspension. Roll the bike and slam the front brakes. Do they stick? Do you have to manually pull up on them to come back? Also check for leaks or any wear items like shock bumpers missing or trashed. Knicks in the lower fork tubes, dents, etc.
- Air Filter. Check it over really good. Also pull it out and stick your hand down the airbox for grit or dirt.
- Engine. Listen to it closely. Some bikes are louder than others but problems will show them selves easily. Any leaks? Work done? Get receipts if anything has been done! Any maintenance logs as well.
Thats about all I got. Dont count tires, or little basic stuff like grips and seat cover cause I usually switch those out anyways and they are cheap enough.
GL!