maybe some pictures might help.
1. clean, make sure arms swing freely
2. clean, make sure no grease/oil on pads nor starter bell
3. the stock weight is fine, how are you adding weight?
4. Anything nee takes time to wear in to fit its applicatuon. The contact surface needs to increase especially when trying to spin a new motor with a kit.
3. ensure belt is in good condition and adjusted properly.
4. run start and jump on.
5. stretch springs instead of adding weight.
nothing is something.