Seeing as you're in the third-world (like me), you might be able to find something similar to what I'm using on my XR650R.
I run a Mitas C-02 in the rear (http://www.justbiketyre.co.za/produc...einf-c-02.html
) and a Metzeler MCE 6 Days Extreme (http://www.justbiketyre.co.za/produc...extremefr.html
) in the front and they're both coping with the weight and power just fine. My tires have thousands of road miles and just as much dirt/mud/sand and they still look great!
Best of all, they're incredibly cheap! Rear is about $70 and front is about $52. That's cheap down here in Africa!