Fork mod

i don't know but i'd really like to know why they did away with the drain screw at the bottom of the forks, on my 91 there was a nice little drain screw on the bottom of the forks, went to change the fork oil on my 99 and well there was not drain screw

Because just changing the oil does not get rid of all the contamination. If you take it apart you will find enough grunge clogging up the works to bother with cleaning it properly.

how often do you need to change fork oil?

i rode my bike a little over two years then it sat in the garage 11 years. when i started ridin it again i knew i had to take a look at the forks left one had a little leak. took em off drained the oil (the little screws at bottom) i thought oh boy black gold, texas tea. anyway i flushed about a quart each thru them of some 15w i bought by mistake, until it came out clean, drained them and filled to 120mm for me with spectro 10w. seem fine and left fork quit leaking after first good day of riding.