What type of motor oil in Yamaha maxim?

You need a 20w-50 or something close to it. Also you DON'T want to use an energy conserving oil, like you use in your car. It will make your clutch slip as it has agents to make it too slick for wet clutches. I use a Diesel oil as it doesn't have the slick agents in it.
You can usually find a 15w-40 Shell Rotella at Walmart and it works just fine for my bike.