I have a generator that can produce 150 watts, i have a dc motor that takes in 100watts, why is it that my generator wont run the motor?
I'm assuming "the exact numbers my generator says it needs to run" is a typo and you mean motor. 

Your issue is likely the start-up current required by the motor is way larger than the run time current. Motors need lots of oomph to get going, 100W is when up to speed only.