xsr

Hello there I have a question regarding xs400 fuel tank. My xs400 is 1980 special model, I want to fit different tank something square ish type of tank. Will the xs400 tank from normal model fit specail frame? Or maybe tank from RD200 looks very similar to the tank from xs400 square type tank. Also I want to fit 2 in to 2 exhaust, my bike came with 2-1 motad exhaust, where can I find 2-2 pipes? Will pipes from another model fit xs400? Thanks in advance Gaz