[rpduc]

Street and dirt{all japanese}

I believe the distinction is dual chamber forks like those on most (?) "modern" Japanese MX bikes and the Marzocchi 50mms like I have on my MC250 have the compression adjuster on top. My Duc S2r 1000 (not dual chamber) has rebound on top. I suspect your Japanese street bikes also run dual chamber forks if the compression is on top. Though I know little about Japanese bikes the OP best consult his manual since he likely has one of each with single chambers on his EC300 and dual chambers on his YZ250.