S50 won't start
 

2007 s50. I got the bike from a friend who was having some trouble with the bike starting. After some diagnostic testing I found that the battery is good, the stator is good, and the reg/rec is good. I just replaced the spark plugs and tried again with the battery on a full charge. I hear the solenoid clicking and the engine is trying to turn over but it does not fire up. The choke is fully pulled out too.

Does it sound like I need to replace the starter next? Should I look into an engine flywheel problem? What else can I try?