How can you build a bobber frame?
Depends on what you mean by "bobber". Traditionally, bobbers are
standard bikes that have had everything not necessary for going and
stopping "bobbed" off, or removed. Remove or cut down the fenders,
strip off the instruments, the big breather box etc.
If you mean how do you build a lowered rigid frame from a
swingarm bike, the easiest way is to remove the springarms and
replace with solid struts, or just remove the springs and weld the
Alternatively, hack off the swing arm assembly entirely and
weldon a rigid tail. For that you need a tube bender and a welder,
plus a grinder etc. (If you're asking such a basic question I am
assuming you don't know your way around a grinder ot welder too
much. Stick with struts.)