I have and ongoing issue with my 86 230s quadsport. the rear brakes lockup after riding my quad about 20 minutes ,i have replaced the rotor/brake pads rebuilt the rear caliper /rebuilt the master cylinder and it still is locking up!!!!!! once the rear brakes cool down then its fine for a little bit
PLEASE HELP!!!!!!!!

 

Did you have this same problem before you done all the replacing mentioned above? If not, maybe something isn't the right part.

 

Do you have the original pads? Where did you buy the replacements? Did you lube the caliper slides real good? The reason I asked about your old pads, and where you bought the replacements is because I tried to replace the pads on my z400, this last weekend and the pads that I bought from a ebay seller, were about 50 thousandths of an inch to small on the hole spread for the caliper pins, slides. I did not use the pads because they did not want to fit right.

 

You may also want to try replacing the hose, some times they get split on the inside and the pressure from the master cylinder will hold flap on inside of the hose closed and not relaese pressure form caliper.

 

Are you using the proper DOT brake fluid?