If you want to leave the motor stock, then you're limited to two choices for hill climbing power (short of losing more weight, though you're lighter than me). Get a bigger sprocket (48T if you're slightly lacking, 54T if you almost stall quickly), but you'll lose out on top speed and use more gas for cruising around [higher RPM], or get a shift kit (I avoid the shift kit honestly, it costs more than the motor itself, but the gearing range would help a stock motor immensely). However if you're willing to modify, all you need is a dremel and some sandpaper to get some extra juice
...for what it does for you so what if the shift kit cost's more money than the motor?
...it's like buying a $2.00 pair of shoes and spending $8.00 on laces, ...if the shoes fit really nice and you like the way they look, who cares that the laces cost more than the shoes?
...these bikes are like a cross between a tool and a toy and the money i spend on tools i consider an investment and the money i spend on toys is for my enjoyment so for me it isn't about the cost of individual parts that's important it's how much fun do i get when i play with my toy.
...i don't have a shift kit yet but it's on the list, unfortunately my bike is a single speed beach cruiser so i can't add the shift kit until i'm ready to add a different, multi-speed hub, ...so for me the shift kit is gonna be an expensive upgrade, well over what i spent on the motor.
...but it WILL get done, i'm really getting tired of pedaling off the line, lol.
anyway, that's just my take on this whole topic.
, bozo