Fuel System
From GummyCarbs
OEM Japanese Fuel Hose
Honda seems to use the "red stripe" fuel line. This can be found at Sudco's site. According to Sudco's site, it's made by Kitaco (likely a shortening of Kita and Company) in Japan. It's available in 3.5mm, 5.5mm, 7.5mm, and 8.0mm inside diameters.
Sizing
Sizes are generally given in terms of:
- Inside Diameter (I.D.)
- Outside Diameter (O.D.)
- National Pipe Thread (NPT)
- Air Force Navy (A.N.) (typically for brake systems, not fuel)
Tank Outlet Size
Most Hondas I've seen use 3/8" NPT outlets on their tanks. Some bikes use custom adapter plates. Later Honda CB750's use what appear to be Harley-Davidson style, 22mm outlets.
Tank Capping
Most gas tanks can easily be capped (for de-rusting, Kreem coating, etc) using a simple, 3/8" brass NPT cap (note: not a plug, which is male-threaded). These are available at most hardware stores or from McMaster.
Fuel Hose Size
Honda fuel line seems to always be 8mm inside diameter (just over 5/16", which is 7.9375").