Join Date: Jun 2009
Location: Gilman, Iowa, USA
Model: 1989 GL1500
You should be able to diagnose if it's your master cylinder or the calipers. To diagnose which one it is:
1. Put cycle on center stand
2. Put a small jack under the engine to lift the front wheel slightly off the ground
3. Rotate the rear wheel by hand - from what you say above it should be dragging
4. Crack the rear bleeder open and then close it.
5. Try rotating the rear wheel again
6. If there is no change your problem is the caliper. If it now rotates freely it's the master cylinder.
7. Same goes for the front - if it rotates hard first crack the bleeder on the left front caliper. If it's free now it's the rear master cylinder. If not, move to the right front. Crack the bleeder - if it rotates free it's the front master cylinder. If not, it's the caliper.
I just went through the pain of removing the rear master cylinder and didn't follow the above list. If I had I would have figured out it was the rear caliper and the right front caliper sticking, and not the rear master cylinder. I got to remove my entire exhaust system and the caliper for no reason...