ready to tear into trans 96 RS A

So I finally got a new master cylinder on the boys bike. rebuilt the clutch slave and adjusted the linkage as good as I could. If I slam the shifter down into first and keep pressure on it, I can use first gear. if I take the pressure off the shifter for even a split second its jumps right out of gear. I'm prepared to tear it down, I just need to know what I should be looking for/at to adjust or replace?

As suggested in your other thread, pull the clutch cover. Check to see if there are any worn parts. The 96 has a different shift segment than later models. There are more pieces to wear out including the cage that holds the pins. The segment from a 2001 is one piece eliminating the cage and is a direct replacement. I replaced mine as suggested when I lost fourth and fifth gear. I think your problem is somewhere in the shift linkage behind the clutch and this would be IMHO the best place to start.

Here are links to the breakdowns so you can compare.

1996= http://www.yamahapartshouse.com/oemparts/a/yam/50043abbf8700209bc78d0be/shift-cam-fork

2001= http://www.yamahapartshouse.com/oemparts/a/yam/5004469ff8700209bc78fb10/shift-cam-fork