They're threaded in place. You need a special freewheel puller (park tool sells them, among others.) To remove the old one(which is reverse threaded) and it can be torqued beyond belief. The new one spins on by pedalling action, so no need to torque that one.
change out the hub
it turns the wheel
Depends on what you want them for. If you want to do grinds, put them on the left side front and rear wheel axle end. If you just want to give a buddy a ride, put both on the rear wheel. For flatland tricks, maybe both sides, both wheels.
There are two different hub designs for BMX, freewheels and freehubs. You need to know what you have if you want to replace the sprocket by the rear wheel.
Where ever he put it last.
they can range from 46teeth on a chain wheel all the way down yo a 22tooth chain wheel.
U don't
duck tape
The key components of a BMX brake system are the brake lever, brake cable, brake caliper, brake pads, and the braking surface on the wheel rim. When the rider squeezes the brake lever, the cable pulls on the caliper, causing the brake pads to press against the wheel rim. This friction between the brake pads and the wheel rim slows down the rotation of the wheel, ultimately controlling the speed and stopping power of the BMX bike.
Yes you can.... you can put any hub, spoke, and rim combinations together...maybe a few ecceptions but you can deffinetly do that... just bring the parts to your local shop and have them lace it.
put my mum on the seat and grind
The BMX bikes that you buy at Target and or Walmart are not the same BMX bikes that are used in BMX Racing and BMX Freestyle. Real BMX bikes are lighter, they have diiferent size sprockets among many other things. Feel free to google the National Bicycle League or the American Bicycle League to get more information.