whats the biggest rear tire i can put on my stock 109,without doing any work done to the rear?

HELLO FELLOW M109ers, I am glad to have found this website. I am a small engine mechanic that has been riding motorcycles before I learned how to ride a bicycle, my dad started me out on a suzuki 80 at the age of 4 1/2. I havent stopped since in 2006 I purchased a silver m109r new, and I just...