What does a restoration involve?
This is up to you, your budget, and how far you want to go. If the bike is already in good running condition and all you are looking for is a repaint/powder coat to the frame and polish of the hardware, this is much less expensive than a bike that is a basket case restoration. Basket Case restorations typically involve sourcing many NOS and aftermarket parts to bring the bike back to life, not to mention additional mechanical work.
