I have No back brakes on a 650 v twin artic cat atv.when I mash the pedal I have no back brakes.I have checked and tried to clean the capliers but I could not get on side out to clean.  

sorry I should have stated that it the foot bakes.  

if they are disk brakes,
check the brake fluid, and check the brake pads,  if these are fine then...
remove the caliper, once you have the caliper off, remove the piston inside.

clean the outside of the pisto removing any rust or build up.
the carefully clean the hole the piston came out of removing any build up or rust.

reinstall then bleed the brake calipers.  

I did that except I can not get on side loose to clean.
I am afraid that I will break it trying to get it out  

I have not got the right amount of brake fluid coming from master cylinder in to the hose that come to the caliper,I have some but not enought,I am not sure but I don't think that it is.  

Hey, had the same problem with two different arctic cats, my 400 and 650 v-twin. Both were 2004. The problem is the master cylinder that is bad. The piston in side actually freezes up and no way to break it loose. I had an extended warranty for both machines and they replaced the master cylinder with updated parts. Now fluid reservoir are seperate units. Works great now on both machines. Hope this helps. By the way if you dont have extended warranty on your machine you can expect to pay about 285 dollars to fix yourself.