A front brake bleeding annoying issue.

Troubleshooting question: I've had this front brake reservoir issue since acquiring my bike last year. Previous owner/s messed with all fluids and I'm correcting them one by one. Purchased with 2600 miles and now bike has 7500 miles on it.

The one I can't get ironed out is the front brake lever mush feel. It only occurs after sitting in the sun all day at work. When I come out to my bike the front brake lever squishes in almost all the way. I pump it a few times to get it firmed up, but not as firm as I am used to on any other bike I've owned and maintained. If it is a cold, overcast day, it does not exhibit this problem.

I replaced fluid and bled front and rear brake masters last Summer but it did not help. I have always done my own brakes on all my cars and bikes all of my life and have never seen anything like this. I am suspecting there is an air bubble trapped in the upper banjo bolt or the master cylinder itself that is expanding in the heat from the sun. I cycled a full pint of brake fluid through the front lines, from the top down, when I did the brake fluid refresh. Keep in mind this problem was there before I did the fluid replace so it's nothing I did that caused it. But I didn't fix it either, using the same top down bleed method I have always used for almost 50 years.

Any thoughts on this or has someone had the same issue on the 8th gen bikes?

 

What bike?

 

2014 VFR 800

 

Sounds like you need a new master cylinder piston seal.

 

Thanks I will research that. I would expect some visible leakage if fluid were getting by and I don't understand the "only when it is hot and sunny" requirement for this to occur.

BTW, why doesn't my signature image show up any more? My Imgur link is still active.

 

I see

 

That's what I am seeing too, and it looks fine in my user setup, but I see your sig just fine.

 

My sig is an actual re-sized photo in the body of my signature field, not linked. Seems linking creates a lot of problems lately.

EDIT: Actually mine is a link too. But it is linked to one of my albums here at VFRW.

 

Putting the lever in the #1 position should give you the best result

 

Hi Suby.
Sad news about your brake issue especially on a relatively new 8gen with only 7500mile, very unusual. Perhaps the previous owner managed to get some dirt/grit into the MC and it has scored the bore or damaged the piston seal.
Agree with Terry and Mello's zip tie overnight thing!

But get it sorted one way or another ASAP you could have a potentially dangerous situaton in your hands!

As for why hot days cause the issue! Can only suspect that the Black MC will absorb a lot of sun heat causing slight expansion of the MC bore this might exacerbate an already marginal situation with the seal or a scored bore - just theorizing a little!

Can assure you, brake and clutch bleeding is a piece of cake on an 8gen. I simply siphon out all old fluid from the MC, fill it with new and start the bleed process, works like a charm, I do this annually.

Good Luck.

 

My 2014 has a squishy front brake too. I remember people complaining about the front brake feel on this 8th gen forum a few years back and I don’t remember anyone really solving the problem.

 

Thanks all : ) If there's a warm day this weekend I will try tying the brake lever and see if it looses pressure.
It's been a cooler year so far and not much sun like we are used too, so it hasn't been a problem most of the time. But I don't like the idea of my main braking force being suspect. When I did the bleed I thought I could see something shiny near the piston of the master cylinder. Odd looking and the thought occurred to me was it a trapped air bubble? It still looked the same after replacing all the fluid two times over. The clutch bled with no issues and works great.

The previous owner of my bike was evidently ham fisted and with no mechanical aptitude, based on the condition this newer bike (28oo miles) was in when it was delivered to me. Stripped and missing fasteners everywhere, bodywork misaligned at tab-lock points, failed attempt to get the oil filter off ( it was partially crushed ), antifreeze low and not Honda coolant, driver seat rubber cushions hack sawed off at different heights...on and on. I spent close to $200 just replacing the stripped or missing OEM fasteners : /

 

SubyRS: Yes, I've had a similar issue on my 2014 Deluxe when I ride to work and the bike sits in the sun all day - The front brake feels very stiff and numb on the first application, particularly when its really hot out (over 95F / 35C). I have even had it happen when I'm on the freeway for hours on a really hot day. I assume it is just heat expansion on the fluid with maybe a little bit of air or water vapor in the line, with the extra plumbing for the ABS system an added complication. It is noticeably less of an issue after a good bleed; I have SpeedBleeders installed to make it less of a hassle and always make it a point to bleed the system at the start of summer when the temperatures start to climb. Other than that, I have made it a habit to pump the brakes a few times when climbing on the bike after it has been sitting in the sun to clear that initial numbness.

-SlideRule

 

Wow thanks, so I'm not the only one. I did the zip-tie on the brake lever and there was no change in the pressure after a couple of hours in the garage. Still taught. I don't have the deluxe so my bike can't use that excuse ; ), and being such a low mileage bike all the components are new. I have the habit of going out to my bike after work and while taking the bike cover off, I pump the front brake 3 or 4 times before I even suit up and get on the bike.

 

Reading thru the comments of another thread it was pointed out that there are a couple high points in the brake line plumbing on the 8th gen - I double checked and sure enough the brake line coming from the front left caliper goes up over the fender and then down to the junction point on the right side, before heading back up to the master cylinder. It might be pretty tough for us to flush out a bubble that may be caught in this area. I'll try to pull the caliper and/or orient the brake lines to eliminate this high point next time I bleed the brakes. Brake line routing has changed significantly on ours compared to previous generations with linked brakes.

-SlideRule

 

That's interesting because an air bubble usually just travels along with the brake fluid movement. If you watch an air bubble in a clear tube you can't get it to stop moving with the brake fluid no matter what angle it's at, or up or down. Cycling a full container of brake fluid through both calipers should purge it all. But, this bike is having an issue that no motorcycle I have ever owned in 47 years has had....so I will look at that also. Thanks : )

 

That's not my experience with small air bubbles. I just bled the front brakes on my Gen 8. I put a clear hose on the bleeder oriented up for 4-5 inches and then down to a bottle. I watched a small bubble come out of the bleeder, travel up to the high point of the hose and stay there no matter how much fluid I pumped through the master cylinder. Maybe it would be different with a vaccum pump?

 

Sorry I've been in Jury Duty with long hours lately. I think what you are describing is cohesion in liquids.
An air gap will not move in liquid captured in small tubes unless some other force or modifier moves it along. This can be an open end and a pressurized end, or some contaminate that acts as a body to coheir onto along the walls of the tubing. If I put more liquid in one end and release pressure on the other end, the air gap (bubble ) will move along. Otherwise an air gap will stay exactly where it is at.

I took a pic of water in a 1/8" ID tube with several air gaps and open on both ends.
The bubbles do not move no matter which way they are oriented. (See pics attached.)
If I blow through one end they will move along, simulating bleeding the brake lines.

I've also done the brake jobs on every car and truck I have ever owned, and most have very high brake line loops to allow for suspension travel. There is no issue bleeding those lines. I don't see how the bridge tube over the front wheel could trap air at all. I am suspecting the master cylinder on my bike. I think there is an air bubble trapped on the piston. I will have time to look into it after the court case is done next week.

https://i.imgur.com/XFmqJ3E.jpg
https://i.imgur.com/bmwM9A0.jpg