If it is just clean the carbs and check the valve clearances then go ahead. If it involves engine rear main seal or anything electrical, then walk away.
Electrical. Maybe throw away the Bosch or whatever and use Japanese stuff. He may have mentioned a fire, but it was working and just wanting to tidy up. We'll wait and see; he's not a man with a lot of free time, so it shouldn't demand much of me.
https://www.2fiftycc.com/index.php?resources/categories/zzr250.40/ https://www.2fiftycc.com/index.php?account/upgrades