can i measure clutch stack hight with clutch in bike i dont have a shaft to do it on a bench or is there another way

why do you need to measure the stack?
Just asking. if you are replacing friction plates, just soak them, and install them. trying to analyze a stack is very difficult, even for those that do this stuff, and you do need specialized equpment, spare parts, and specialized knowledge. Leave it to say, if you buy OEM friction plates, soak and install them, you will be safe, if you start replacing metal plates, you need to measure the ones you are replacing, and purchase accordingly. The stack should not vary based on this.

if you have access to a granite table, and a height gage, measuring the stack on the table, minus the outer friction disc, and creating a mirrored stack height is the best and easiest option. Stack height on a worn clutch (burnt) varies only about a 1/2 thousandth of an inch from a new stack....it's the glazing and burnt surface that is the problem...

the book says measure stack hight free play (clutch is assembled) but i"ll trust your experiance thanks

The issue of stack height is primarily because these bikes have a slipper clutch, and the slipper function is controlled in great part by the stack height. The reality of it is to just assemble as MOB stated, then if you need to tweak the slipper action, then you need to replace a couple of the steels with thicker or thinner, depending on if you want more slip (thinner) or less slip (thicker). HTH, Steve