Well if you want just a backyard bike, I'd suggest going with this setup. Its perfect for a backyard ripper. Also a very fun bike haha I just took off my mod 50 parts (zokes, +4 swingarm, billetware frame) to go back to a stock bike as a backyard ripper.
-Rear shock (any good aftermarket company - Ishock, Elka, Works, Fox... etc)
- Tall Bar Kit ( Really helps the handling of the bike, better suited for an adult)
-Tall seat or Stock seat with gripper cover ( either or really, just preference of the rider)
- HD springs for stock forks ( Really helps for jumps/bumps for an adult rider)
-88 kit ( not needed but you can get some cheap kits that will wake up your stock motor)
Really thats all you need for a good backyard bike. Hope this helps