Motorcycle Repair: bike sat, wont start, cb750f, spray bottle

Question
I just purchased a 1977 cb750f. Has sat in garage for over 3 years. Won't start, just cranks. Owner says he cleaned fuel tank, changed filter,cleaned screen. How can I check for spark and fuel?, any basic maintenance tips and tricks that may be partial to this model to start without spending a millin dollars at a garage. Any help greatly appreciated. THANKS

Answer
Take a plug out and ground it on the head when you crank the motor you will see spark.I think you will have to clean the carbs.I use a spray bottle with gas in it to spray into the carbs.If it starts after spraying gas in the carbs you need to clean the carbs.