Motorcycle Repair: Yamaha Zuma wont start, fuel injector cleaner, oriellys

Question
Bought a Yamaha Zuma 1998, 50cc 2 days ago. The guy said it was in fine condition. 4200 miles on it. As i was leaving his hous it stalled on me at intersections when i let the throttle all the way off.
after work it would not start. the seller told me i probably flooded the spark plug, so i let it sit to dry overnight. in the morn it started up fine. drove it good amount then it dies as soon as i stopped it will not start now.
He had the bike in the garage for some months. i have been told that i need to to basic maintenance, replace battery and clean different parts.
can you plz list off the things i should check/ clean/ buy/ replace? i know very little about bikes. thank you!

Answer
Estevan, Unfortunately the fuel we get now doesnt last long. The octane is lower but is boosted up with things like propane which goes away in 30 days. Try this first put in a new NGK brand spark plug. The stock one is a BR8HS. Try one step hotter a BR7HS,pick up one at an auto parts store like NAPA or Oriellys or Auto Zone they are usually cheaper than a motorcycle shop. The carb could even have the jets plugged or restricted from a fuel gunk build up. The carb may have to come off and be cleaned and reset. If you dont feel comfortable doing this have a trustworthy shop do it. Also get a bottle of Lucas fuel injector cleaner and put in 1/2 of the bottle and fill the tank run this out then put in the other 1/2.It will be strong but will help break down the sludge and help it pass through the jets easier to be burnt. Start here first.