Well today i was jus cruzin down the road in 6th gear at like 1/4 throotle when all of a sudden the rear tires just locked up. I thought it was my rear brakes but it wasnt. I can start the bike and it will run but when you let out the cluch it stals and acts like the rear brakes are locked. I can only mannage to shift it down to 4th but no lower and can ride in 4th but soon as i try to shif to 5th the rear wheels lock. Whats wrong wiht it? Any help would be nice