Space between frame and tank?

Hi all,

Any idea how much space there is between the top of the frame and tank? specifically for a '77 cb400f? im gonna try to re route some of the wiring in the headlight underneath the tank if possible? Anyone think this will cause me some kind of problem down the road?
TIA

I have one of these and, like most bikes, there is a pretty good amount of clearance between the frame and tank tunnel. "pretty good amount of clearance" is - well, pretty subjective! You can take some modeling clay and put it in a plastic bag and crunch it in between the tank and frame in the places you are interested in when installing the tank and then take it back off and see what you get. Be advised, rerouting stuff on motorcycles is not amateur hour. Cables, wires, fuel lines, etc may look like child's play, but re-engineering these very simple things so they do not give reliability issues is much more challenging than it looks.