i'm new...sorry

so my buddy brought over his bike(1971 suzuki ts 90) that was given to him for free, it ran 6 months ago when his brother was riding it...now it won't start up...i took off the carb(mikuni) and cleaned it, was pretty clean to begin with..put new gas in it...he said his dad put a new spark plug in it 6 months ago...i had it started for around 5-10 seconds this morning a couple of times, but it seemed like it flooded out....being new to bikes i have no freaking clue what i am doing, so any help or suggestions would be greatly appreciated.