Yesterday, as I started on a short ride, I noticed that the play in my front brake lever was less than normal but I didn't think it was an issue. I was in town on a street with little traffic. As I was approaching a stoplight, I started losing RPMs. I checked the front brake lever and it was hard as a rock. I stopped at the light and was going to pull around the corner and off the road, but when I released the clutch the bike didn't move and subsequently tipped over, pitching me on the grass just past the curb. I was pleasantly surprised with the outpouring of the offers to help from this relatively big city's residents. The guy behind me helped to get my bike back up as my distance from the curb somewhat limited my ability to do it myself. Anyway, long story short, (including cop blocking traffic and wife bringing the allen wrench I didn't have), I was able to remove the rotor cover and then the bleeder on the caliper to release the brake pads. Has this happened to anyone else and what did you do to identify the problem and resolve the issue?
Your problem is the return hole in the brake master cylinder is clogged. Remove the cover and there is a little tab in the bottom of the master cylinder that covers the return hole. It is very tiny and easy to get clogged up. Take a small wire, single wire from wire brush works, and poke it down the hole to clear it. Also a small guitar string or a welding tip cleaner works well.
Then clean it good and bleed the brakes. Have you been bleeding your brakes regularly to keep fresh fluid in them? If not, you should do that every year or two.
That small hole is called a compensating port. I once had the same problem with brake lock up that was caused by a replacement brake lever handle not fitting correctly. Had to remove the handle and grind some off so it didn't cover the compensating port when fully retracted. If the lever doesn't fit right in, it will be a problem.
Ride safe, and smart. Asphalt is like #1 grit sandpaper. Dave
Weirdest thing. Did all of the cleaning up of the calipers and installed new pads. Drained the master cylinder, flushed it with 12 refills until it came out clear. Also cleared the tiny return hole in the bottom of the cyclinder.
Hooked the hose up, via the banjo bolt and could get no fluid to come through. Tried Mity-Vac, same results. Finally pulled the banjo bolt at the FULL master cylinder and not a drop came out when I pressed the lever. Trying desperately to find either a new master cylinder or a rebuild kit. I go on a long-distance ride on Monday, so I am in a bit of a jam. Have ordered both the master cylinder and rebuild kit but am not confident that they will get here on time.
Corkster52 wrote: ↑Wed Aug 18, 2021 9:29 pm
Weirdest thing. Did all of the cleaning up of the calipers and installed new pads. Drained the master cylinder, flushed it with 12 refills until it came out clear. Also cleared the tiny return hole in the bottom of the cyclinder.
Hooked the hose up, via the banjo bolt and could get no fluid to come through. Tried Mity-Vac, same results. Finally pulled the banjo bolt at the FULL master cylinder and not a drop came out when I pressed the lever. Trying desperately to find either a new master cylinder or a rebuild kit. I go on a long-distance ride on Monday, so I am in a bit of a jam. Have ordered both the master cylinder and rebuild kit but am not confident that they will get here on time.
If you've got the new parts coming anyway, why not pull apart that master cylinder and see if there is something obvious blocking it? Pull the piston out of the master cylinder, clean out any gunge, make sure all the ports are clear, give it a good cleaning. You might get lucky and fix the problem without parts.
WingAdmin wrote: ↑Thu Aug 19, 2021 9:08 am
If you've got the new parts coming anyway, why not pull apart that master cylinder and see if there is something obvious blocking it? Pull the piston out of the master cylinder, clean out any gunge, make sure all the ports are clear, give it a good cleaning. You might get lucky and fix the problem without parts.
I was hoping the same thing! I didn't know the extent of the damage until I dismantled it after returning from vacation. Turned out that the piston seals that I received the afternoon before leaving were the wrong size. They sent me the seals for the left side, which are smaller than the ones to fit the larger right side pistons, but the old ones looked in decent shape so I kept them...but I was fooled into thinking they might have been the "smoking gun" as I flushed 10 times through the master cylinder but was still getting some amount of gray material coming up through the suction port of the master cylinder each time I pumped the lever multiple times.
I disconnected the hose to the brake at the master cylinder and I saw a lot of gray material. I removed the master cylinder and pulled the plunger/piston and it was really dirty and the majority of each of the 2 seals (which actually work as cups) had more gray stuff in each of them. I cleaned them up and cleaned the bore of the master cylinder, along with clearing both the suction and return ports in the bottom of the master cylinder, hooked it all back up with the hose disconnected at the caliper, and pumped the lever...nothing came out. Then I looked at the banjo bolts that connect the hose on each end and some of the gray material was in them as well, cleaned them and suspected the same might be happening inside the hose....so I tried as best I could to blow compressed air through the hose and some air came out. Decided ****, I'll bet the hose is partially plugged..so AHA..I had a new hose that a friend had given me 3 years ago in Ohio, still in its original package! Jerry-rigged the new hose into place and NOTHING but a few drops came out of the disconnected bottom end of the hose.
I also got online to see if there were any "how-tos" that might be beneficial. I found one video (skip to 1 minute so you don't have to hear the rest) about doing a bench test of a master cylinder. I did the same test he did and passed just like his. [url]
Something about this whole issue still sounds fishy to me though, because after I released the pressure on the frozen brake that dumped me, 2 blocks later on the ride home, the front brake came back to normal.
I have ordered an entire master cylinder but I don't think I will receive it until after Monday, which will cause me to miss the only GATHERING I have taken part in If, by chance, my situation changes I'll be there
Any further suggestions that anyone can offer would be greatly appreciated! This old man has been pulling my hair out on this
Ended up, due to timing constraints, installing an aftermarket (Chinese) front brake master cylinder. It is a smaller size and does not (at least so far) have the stopping power that the OEM does, but it will do for the short term. Had lots of friends helping me on this issue and like to thank them all! Headed to Wise VA for the GATHERING!!
I decided to flush and bleed my clutch too since I already felt like I'd been bathing in brake fluid for 5 days. I tried using the Mityvac, but could not get it to work. The speed bleeders worked pretty well though.
One "trick" I did learn about on YouTube (at 4:20) was to crack the banjo bolt just a little to speed up the bleeding process without needing to open the bleeder. I could hear the air being released as I did it
Now, if I can just figure out how to adapt the 2 prong connector coming out the bottom of the Chinese master cylinder so I will have, at least the brake light, working when I apply the front brake. There is a 4-wire connector that was connected to my OEM master cylind
Darn...dumb and dumber I guess. Turns out the 2-pronged connector was for older bikes that had just 2 wires to connect. As soon as I removed the screw for the added connector my wiring nested right where it should be....including the notch for the post on the bottom connector!
I can attest to not leaving home without a PHONE when you take tour two wheel stallion for a test drive after the repair. My brake locked up 4 blocks away. No phone, no tools and stopped in the middle of the street. Talking about being embarrassed!!!! Had to walk back home in 94 degree weather. Drove back with 10mm wrench to free the bleeder. Rode the bike back and then had to walk back to get the car.
Now, i can attest to the fact that you have to use the strong steel wire to clean the return hole. Compressed air did not work. Had to tear it apart twice. Once it is cleared you can bleed it properly.
maugliavus wrote: ↑Mon Sep 04, 2023 3:21 pm
I can attest to not leaving home without a PHONE when you take tour two wheel stallion for a test drive after the repair. My brake locked up 4 blocks away. No phone, no tools and stopped in the middle of the street. Talking about being embarrassed!!!! Had to walk back home in 94 degree weather. Drove back with 10mm wrench to free the bleeder. Rode the bike back and then had to walk back to get the car.
Now, i can attest to the fact that you have to use the strong steel wire to clean the return hole. Compressed air did not work. Had to tear it apart twice. Once it is cleared you can bleed it properly.
Phone!!!- Don't leave home without it!!!
And for a Goldwing...never leave home without a 10mm wrench!
The guy behind me helped to get my bike back up as my distance from the curb somewhat limited my ability to do it myself. Anyway, long story short, (including cop blocking traffic and wife bringing the allen wrench I didn't have), I was able to remove the rotor cover and then the bleeder on the caliper to release the brake pads. Has this happened to anyone else and what did you do to identify the problem and resolve the issue? 
If, by chance, my situation changes I'll be there 
Turns out the 2-pronged connector was for older bikes that had just 2 wires to connect. As soon as I removed the screw for the added connector my wiring nested right where it should be....including the notch for the post on the bottom connector!
