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+--- Thread: Front Brake Drag (/showthread.php?tid=4845)
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Front Brake Drag - 2017EX_imp - 03-26-2020
The end of a long saga with the front end of my 2017 CB1100EX has thankfully finally come to an end. From the start, I had an annoying front end vibration that appeared around 35 to 40 MPH, and smoothed out around 50. Numerous trips to the dealer mechanic, then changed to a mechanic at another dealer, as well as numerous calls to Honda U.S.A.. The second mechanic found my front rim ( spoked ) to be out of true-out of spec both up/down and side to side. A flat spot on the front tire was also found. The rim was trued to spec, front tire replaced, wheel assembly balanced. Vibration gone.
When I am not riding it, I keep the bike on center stand. Recently I bought a Pit Bull front fork lift stand, which when used in combination with the center stand, keeps both front and rear wheels off the ground. Using the center stand, I had always been able to hand spin the rear wheel. Even dragging the chain, giving the rear wheel a hand spin resulted in 2-3 revolutions before stopping. Now using the front fork stand, I discovered that the front wheel would not even make 1 revolution, and disc drag was very audible.
The first attempt to reduce drag and produce a more free wheel was a complete hydraulic flush/new Honda fluid. It was time for new fluid anyway ( the original fluid was then about 3.5 years old ), and did the clutch as well. No change in free wheel. So, I bought all new front end caliper seals, and dropped my bike off at the dealer for a thorough clean and caliper rebuild. My hands are not as steady as they once were so I leave handling caustic brake fluids to someone with better hands than mine.
When I picked my bike up, the mechanic had a grin on his face. He held the rear end of my bike down on the center stand, elevating the front wheel. I gave it a hand spin, and the wheel spun 5-6 revolutions, with only the normal ever so slight hint of disc contact. He said when he took the calipers apart, they were clean inside, including in the grooves under the original seals, and that the caliper pistons did not have any build up that would cause sticking. The brake discs he found to be true, and not warped, which came as no surprise because my bike is low miles, and the only possibility there would have been an unlikely factory defect. He said that he was scratching his head trying to figure out what was causing the drag, and then tried something. He said he stuck a wire in the fluid passageway hole at the bottom of the master cylinder reservoir. When he did that, he said he felt resistance that he cleared and flushed. Something had been partially blocking that internal fluid passageway. Was it a manufacturing burr, or a piece of grit introduced during manufacturing? We will never know the answer to that one. He said he felt that the partial blockage was causing pressure in the system that prevented the caliper pistons from fully retracting. New seals installed, and brakes bled.
Could I have continued to ride with it as it was? Yes, I probably could have, but I knew it was not quite right. When I first discovered the excessive drag situation, I contacted my old riding buddy Jim, and asked what the wheel spin was like on his 2014 CB. When he replied that he was getting 5-6 revolutions with just the normal slight hint of disc drag, my suspicions were conformed. At the very least, a story that might be interesting, and a diversion from thinking about the Corona Virus mess. At most, if anyone else has a similar situation, and wants to correct it, I have passed on one potential cause to look at.
RE: Front Brake Drag - pdedse - 03-26-2020
Thanks for the info, and glad you got it fixed. I've noticed not vibration that you refer to on my '17ex...but I am wondering if you had (still have?) the front brake squeal. Is that still there if you had it before all this work. My brain tells probably not related, but I've been in front of the computer screen waaaayyy too much lately and it's not working as well as it could...brain, computer is fine.
RE: Front Brake Drag - 2017EX_imp - 03-26-2020
(03-26-2020, 03:29 AM)pdedse_imp Wrote: Thanks for the info, and glad you got it fixed. I've noticed not vibration that you refer to on my '17ex...but I am wondering if you had (still have?) the front brake squeal. Is that still there if you had it before all this work. My brain tells probably not related, but I've been in front of the computer screen waaaayyy too much lately and it's not working as well as it could...brain, computer is fine.
Under normal circumstances waaaaay too much computer screen time would not be a good thing. On the other hand it is probably good that we have computer screens as a diversion during this pandemic, and to stay informed. Before the caliper rebuild, I did not have a squeal per se. What I had was more like a ringing, something like when you tap a tuning fork. I have not noticed that since the rebuild, but then I was not looking for it either. Next time I ride I will pay attention to that and report back.
RE: Front Brake Drag - max - 03-26-2020
That's very well done 17EX, i find these repairs with an explanation at the end very helpful and the internet has been so helpful in finding answers and inspiration.
Very precise explanation and it shows the quality of the mechanic in question, i had a similar issue with my 2006 honda cb900 which has the same brake parts, the front brakes dragged initially and freed up with some use but the situation got worse over time, changed the brake fluid, no change, took out and cleaned the seals and pistons; no change.
The only parts left were the master cylinder, it felt "sticky" , it turned out that the rear seal had swollen and was too big in the bore causing the drag, i gradually dressed it up with wet and dry sandpaper and that freed it up enough to make it work as it should but replaced the whole assembly in the end, i also had the problem with my 1977 honda cb550 which developed a blocking of the small hole and came right after careful cleaning it, i could not get the pressure to build up before that because the air could not escape through it.
I did not even know that the small hole existed and only found out after a clear picture of it on the net.
This tiny hole is the only vent the fluid has to reset and relieve any air and surplus fluid from the brake calipers, it lives under the stainless deflector on the bottom of the reservoir and as soon as the first seal is pushed forward to engage the brakes is behind the seal which is why it has to be so small.
The bigger hole is only there to return any fluid that may pass the main seal on the front of the piston when pressure is applied and has no connection to the pressurized part of the system.
The second seal on the piston is there only to stop any fluid that is not under pressure from leaking out of the cylinder, it is never under pressure and just wipes the fluid back into the reservoir.
Here is a link to a video showing the repair of the main piston with a small trick i used to hold the spring pressure in to make it easy to repair;
https://www.youtube.com/watch?v=QM5Wh6GsLO0
Thanks for posting your solution.
RE: Front Brake Drag - the Ferret - 03-26-2020
wow sounds like a thorough mechanic. Good deal and congats on getting it fixed.
RE: Front Brake Drag - Gone in 60 - 03-26-2020
My motorcycle mentor, a wise old sage, left terra firma a few years ago. Now, he appears as a transparent apparition of himself, like Obi Wan or Yoda any time I get stuck with a motorcycle conundrum. He had taught me the trick of clearing very small passages like that, in the brakes and in carburetors, by stripping back a single strand of speaker wire and snaking it through. I had the same problem you described with my old Nighthawk, and that same passage cleared up with a wiggle of speaker wire.
RE: Front Brake Drag - dave - 03-26-2020
Great post; informative and well written. The rear brake on my VFR800 has the same problem. Can this hole be cleaned out without disassembling the master cylinder?
RE: Front Brake Drag - 2017EX_imp - 03-26-2020
Dave, All I can tell you is what my mechanic told me, that prompted me to post the problem and the solution. Max has actually done this fix before, so maybe he can answer that question for you.
RE: Front Brake Drag - Guth_imp - 03-26-2020
FYI, this is the content from a post I made over on the Hawk GT Forum many years ago...
I picked up my Hawk a couple of years ago. It's an '88 model, all stock, and about as clean as can be, just beautiful to look at. I was pretty happy to find it.
However, like yours, my Hawk had been sitting for an extended period of time and the brakes needed some attention. My front brakes ended up locking up - fortunately I could tell something was up and had slowed down to a crawl, the bike and I were both unharmed.
In my case, it turns out that the front master cylinder needed to be cleaned out really good. The fluid had started to turn to crud and the tiny return hole had clogged up. In addition the cylinder surface needed to be polished (I used some really fine steel wool attached to a short length of plastic tubing attached to a drill). I would have never suspected it when first looking the bike over. I've read of others here having the same problem as well. Just be sure to look everything over well before you really start racking up the miles. I know that I'll be sure to dig through things more thoroughly should I buy another used bike.
What is interesting is that when I first got home from Seattle where I had bought the Hawk, my buddy (who had a truck and drove) had backed into our driveway so I could just roll the bike out of the bed, down the ramp, and then into the garage. Of course it was a beautiful warm June day and a number of my neighbors were outside and watching everything. After loosening and removing the tie-downs, the bike would not budge — at all. The front wheel was completely locked up. Since my neighbors were watching I couldn't throw my normal pissy-fit. Realizing it might take me a while to figure out what was going on, I went inside to get a couple of cold beers for my buddies who had travelled to Seattle and back with me that weekend. I figured it was the least I could do, especially as I wasn't exactly sure how long it would take me to come up with a solution that would not make me look like a bigger idiot than I already did — or one that would risk eventually dumping the bike over. By the time I got back up in the bed of the truck to check things over again, the front wheel rolled just like normal again, easy peasy.
The eventual front brake lock-up event made for a good story as well. I had been working to get everything working just right on the bike and had already rebuilt the carbs. The front brake issue was the next big thing that I was trying to take care of. I had had the bike out for a few short test rides when I was working on the carbs and I could feel pressure building up in the front brake lever if I rode far enough (and I was not going far at all). On that day when I started looking into the brake issue I cold feel the lever had almost no travel at all so I slowed the bike to a crawl. I mean really slow.
What was funny was that one of the other projects I had on my list was to replace the tires as those that came with the bike were pretty old. So when the front brake locked up completely I was not exactly aware that it had happened until the bike itself got super squirrely. By the time I had figured it out it was too late, the bike was already starting to fall to the left (fortunately I was almost hugging the curb on the right side of the street by then). Since I knew the bike (my brand new to me dream Hawk!) was going down, I ended up sacrificing myself and brought it down sort on top of my like one of those rodeo cowboys bringing down a calf by it's horns (although I was much more gentle with my motorcycle). The bike ended up fine, without a singe scratch on it. I nicked my helmet up just a tiny bit as I ended up doing a full roll like a kid in gymnastics class. It all happened in super-slow motion. My leather jacket didn't even have a mark on it.
I looked around to see if any of my neighbors had seen me and no one appeared to be outside. I managed to get the Hawk upright and the kickstand down. Then I walked back around the block to my house to get a wrench so that I could crack the bleeder valve open just enough free some pressure on the calipers. Then I pushed the bike back home. I figured out in my case that it did not take much heat at all to cause the brake fluid to expand. With the tiny return orifice closed off, the only place the fluid had to go upon expanding was into the caliper's piston cylinders. Eventually things would get bad enough that the front wheel would lock up.
It was a very good lesson learned, and as it turns out, my experience has proved to be helpful more than once in helping people diagnose braking problem where they ended up in the same situation as 2017EX (and myself of course).
RE: Front Brake Drag - max - 03-26-2020
Nice realistic story Guth and no doubt repeated many times over by owners of these mature bikes, initially i had no idea the tiny hole existed in my old honda so i understand why it's hard to find.
Dave, as far as i can tell it seems easyer to at least unbolt the m.c. since the tiny hole ( there are two holes just like in the front master cylinder) is under the part honda calls a "connector" which is the plastic elbow that is bolted to the m.c. and connects to the reservoir.
Since this part has to be removed all the fluid has to be drained from that supply hose.
Once the connector is unbolted the small hole should be in that cavity together with the bigger hole i talked about previously.
The banjo bolt may be left as it is and no additional bleeding required depending how good you are.
All these master cylinders appear to be the same over the years.
Here is a link to a clip that shows how the rear brake caliper is supposed to operate;
https://www.youtube.com/watch?v=nFcrdAEVAQY
And one on how to disassemble what's inside although you may not have to do that but just to show what the m.c. looks like in there;
https://www.youtube.com/watch?v=3LUL55mJzOw
If a copper wire is not strong enough you may be able to sharpen a single bristle from a steel wire bush or a small needle to do the job, just be careful to not produce a burr on the inside of the cylinder that could damage the rubber seal when it wipes past it.