Welcome to the fold, what country are you in? Asia is a big place That naked 400 is a rare machine, a few came like that as standard and were used for rider training in Japan with a few modifications. I have only seen one ever in the UK. There should have been a small fuel filter in the fuel line as standard.Your leak sounds like dirt in the needle valve and drain the carb float bowl normally clears it.The red Suzuki with the red cam cover is the one with variable valve timing, not to many of them over this way. That one looks very clean.What model is the black Suzuki?
By the way, your English is very good. Better than some of ours
Interesting and very effective modification and it looks very like the training model in Japan.How did you get the Speed odometer to function, did you just use the wheel sensor and speed odometer cable from the XJR400?The FZ400 and FZS600 share the same disks and wheels as the XJR400.