Bought a few used bike and I learned from a guy named Ayah Pong (search him in Facebook he provides inspection services). Also some background engineering knowledge from my job as a technician.
Basic basic checking
1. Check starting motor smoothness. It shouldn’t take more than 2 efforts to start when using the electronic starter with a good battery. If you hear grinding sounds when starting and fails to start… just avoid the bike.
2. Test ride. Check front brakes, should not be squishy, firm and progressively feedback as you apply more pressure. Rear brakes gives less feedback but logic is the same.
3. Test ride. Check gear shifting smoothness. Missed gear shifts or abrupt drops back to neutral big red flag.
4. Static test. Pump the front brakes check the front forks for oil leaks. Touch the forks see if there’s oil.
5. Static test. Check if the condition of the overall body and disc rotors tally with the mileage of the bike. Suspiciously low mileage? Disc rotors should tell the truth. It’s not uncommon for touch up paints to be in high mileage bikes, it’s normal. What’s not normal is repairs to hide accidents. I’m afraid I’m not super knowledgeable in this. But obvious suspects, super shiny new radiator with new hoses? More than something just hit the radiator..
I just ask the owner if he jatuh bodoh before. Also do a CTOS total loss claim if you want on the chassis number (ask to share Geran)
6. Static test. Bring along multimeter. Set to DC, check battery condition should be 12.1x (at least 50%charged) above depending whether the owner drive long or short distance usually (Google charge state to get more detail). A lithium battery will be higher voltage at 50% SoC. Then after that, start the bike. The reading should be around 13.1x to 14.xx. It should rise and fall as you rev it up. Number between 12-13V indicates a weak charging output. Anything lower than 12V or stuck at >14.6V should be suspect as the alternator system is problematic. Usually either the stator coil or rectifier.
7. Major service evidence. >40-50K mileage. Ask if valve clearance has been done before..
I’m not a mechanic, just some basic understanding of electronics and stuff I learnt from my own bike service manual and also sifu online. Hope it helps.
True, but i'll check visual(underseat wiring) and static test checklist before requesting test drive. If its not good, I dont even bother to test drive, otherwise, they claim damage is done by me. haha