bottom end

hi
im fairly new to this , but my ebay bike is really hard to get movin, once it gets goin its fine , but im lookin for a bit more power to take off , so iwas thinkin either i can add more teeth to the back sproket or take some teeth from the front , or maybe i need a better clutch to grip a bit earlier an tighter ,
so if i change the number of teeth on the sprockets do i need to purchase a new chain ? or are there some other methods to acheive bottom end , i only have a tight area to ride in so power is much more important than top speed in my case
any suggestions ?

10 turn heavy duty springs and a few more teeth on the rear should do it

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