HONDA 350 RANCHER WITH REAR DURM BRAKES. BRAKES ARE VERY BAD WHAT IS THE SOLUTION

I'm not a honda guy, but braking systems are pretty much all alike. First off, do you know if the rear brakes are mechanical (cable) or hydraulic (fluid)? If it's mechanical, the cables may be rusted and not allowing free movement of the brake mechanism. Pentrating fluid in the cable might work, but if they're bad off you might want to replace. On a hydraulic system, it could be a bad master cylinder or wheel cylinders. Then there is the possibility the brake shoes are toast or there is hydraulic fluid on the shoes from a leaking hydraulic fluid from the wheel cylinders. Some braking systems also require periodic adjustment. Someone might have more specific info on your model.

to ATVQS.

I owned a 04 model once. The front brakes on it was hydraulic drum and the rear was cable operated drum. It tells in the owners manual on how to adjust them on the front (have to remove wheel and red plug). They adjust like you do rear drum brakes on cars. The rears are adjusted via a cable on the rear with wing nuts. If that doesn't help, you might need to get a service manual for proper repair. Oh, to the Quad Squad.