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. They claim it's made by Kitaco (Kitako seems more likely) 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)
Tank Outlet
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.
Capping
A gas tank can often times be capped (for de-rusting, Kreem coating, etc) using a simple, brass, 3/8" NPT cap (note: not a plug, which is male-threaded). These are available at most hardware stores.
Fuel Hose
Honda fuel line seems to always be 8mm inside diameter (just over 5/16", which is 7.9375").