My 86 Quad runner has been a champ since I got it.Like all atvs it gets ill once in a while.I last rode it 12/15, no problems and nothing extraordinary to report.This morning,in a heated garage where it resides on its off time,I cranked it up in 2 pulls.I went to go around the car and I had no brakes.I investigated this evening and here is the lowdown.I lifted the front wheels off the ground. Rear brakes are fine.
1)The master cylinder was full
2)The brakes would eventually grab if I pumped the brake lever enough,However I was still able to turn the wheels
3)the lever is squishy,and there is hardly any resistance when pulling it in.
4) All brake lines are visably good and no leaks seen on the floor

Just in case;it is a 230cc dual range shaft drive model with no rear suspension.Brakes are (1) rear drum,manual,and (2) front drums.It is an '86.

 

This happened to me once, The brake lever perch came loose and went upside down, I think that the little bit of air that was in the master cylinder got into the line, anyway... try bleeding them.

 

How do I bleed them?

 

make sure you reservoir is full and then pump your brakes until is feels firm and hold the lever in. on you caliper there is a bleeder, it looks kinda like a grease fitting and should have a rubber boot. while holding in the brake lever loosen it until fluid comes out, when your lever comes all of the way in hold it there and tighten the bleeder back in. you can now let go of the lever. check the reservoir and then do it again. if you are getting just clear brake fluid with no air then that side is done. you will know if it has air because it will kind of "spit" at you. anyway repeat this for the other side. make sure to have some brake fluid handy, and keep an eye on the reservoir. if it gets empty or low enough to suck air then you will have to start over. also make sure to keep the lever pulled in until you get the bleeder tight or it will draw air back through. I might help to have a buddy help you do thid because it can be a hard reach... hope this helps