rear brakes

Have you adjusted them, and did you get any oil or grease on the pads or drum when you reassembled them?

The brakes should be adjusted so that you feel some resistance when you turn the wheel. Not a lot of resistance, but it shouldn't turn completely freely. In other words, adjust the brakes to where you feel the pads begin to rub, and then back it off a hair.

I'm not familiar with that machine, but I would guess there is a wing nut where the cable attaches to the brake lever. Turn that clockwise to tighten it.

Look in your manual for details.

Take a picture of the rear brake assembly and post it for us.

Or, look through the forums for similar threads, someone has recently posted pictures of how to adjust brakes.

ADDED: Helmut gave you a link to a manual in your other thread!

OK, They're hydraulic disc brakes, have you bled them properly and filled the fluid?