Help tweak my routine

[osiris85]

I've been lifting for about 1 1/2 years, I am 6ft and i went from 170lbs to 205..Now i am at about 195..Now that i have some decent size, I would really like some muscle seperation, and want to tweak my workout and hit it in a diff way..
here is current:

Mon: chest/shoulders

3 sets chest: 5-8 reps on compound exercises..8-10 on isolation

2 sets of shoulder: same as above

2 sets back 6-9 reps

Tues: bis/tris

3 sets bis: 6-9 reps

3 sets tris: 6-9 reps

Wed: legs/back

4 sets of legs: 10-12 reps

Thurs: repeat mon

Fri: repeat tues

sat/sun: off

I didnt list specific routines because I change them every two weeks..The reason I work parts twice a week is I dont wont to overtrain a muscle in one session, but I am starting to think twice a week may be doing just that..I am open to suggestions..

thanks in advance..