I have an 08 Concours (Non ABS) and several months ago, I noticed that after the bike had been sitting for several weeks, the brake lever would nearly reach the grip before meeting any resistance. It had been several years since I had done a fluid change, so I did a change and fully bled the system per the procedure in the service manual. Problem solved; nice firm brakes again. After returning from a 3 week car trip, the first time I went to ride the bike, the brakes were soft again! I re-bled the master cylinder, and bubbles were expelled once again, but normal brake function was restored. 3 days later, I feel the lever getting soft again. Thinking about it, the fluid replacement procedure in the service manual doesn't expel any contaminated fluid from the calipers, since the bleed ports are at the top of the calipers. Could this be the problem? Do I need to completely expel the old fluid from the calipers then refill & bleed the system again? Or is there something else I'm missing? (No sign of fluid leaks anywhere.) Thanks in advance for any suggestions!
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Recurring front brake system problem
- Thread starter Kirk
- Start date
Your symptoms sound like worn seals that are letting air into the system. Since you are not seeing fluid anywhere… I might start with a master cylinder rebuild. There is one at a place called Brake Crafters https://brakecrafters.com/products. If it is the calipers… Murphs has a kit available. Hoping it is not corrosion within the bore of the MC or calipers.
The Brake Crafters kit looks to be fit ABS only. Parts Unlimited has one via eBay…..https://www.ebay.com/itm/293797590337
I know of 2 other Members that have had the same problem.
Both went thru bleeding, rebuilding, part replacement, etc etc.
One solved it by tightening the banjo bolts.
The other still hasn't found a solution.
NOTE: He felt that the aftermarket Master Cylinder kits piston lip location was below the OEM and tried that too.
Ride safe, Ted
Both went thru bleeding, rebuilding, part replacement, etc etc.
One solved it by tightening the banjo bolts.
The other still hasn't found a solution.
NOTE: He felt that the aftermarket Master Cylinder kits piston lip location was below the OEM and tried that too.
Ride safe, Ted
I solved my air-getting-in problem with a Kawasaki M/C rebuild kit. All Balls kit failed, I have the warranty replacement kit for sale if you want to give it a go! My next problem is a soft lever that I just got narrowed down tonight. It is the left caliper circuit, ftom the ABS unit to the caliper. The caliper is ok, it was bolted off to test. Air is trapped in a high spot and so far I can't get it out. I've tried all my tricks, tomorrow I buy a pneumatic bleeder.
I had this trouble back in May. I even use a pneumatic bleeder and have never had any problem in the past. But this time I pushed the pistons all the way in to squeeze out all the old fluid. That was a problem. I didn't get any pressure at all until I removed the caliper and held it almost horizontal with the bleeder just slightly high. It still wasn't perfect until I rode it for a good while and bled it again. It's now back to perfect. If I have this trouble again, I'll try vibrating the caliper with a sander.
Have you ever checked the master cylinder for signs of wear, damage, or contamination? The condition of the piston seals and the master cylinder bore is essential for maintaining the proper brake function. In case of any issues, rebuilding or replacing the master cylinder might be necessary.
Are you fixing brakes?
I am trying this overnight tonight. What is the reason for holding it horizontally? It seems as if vertical is best as the holes between pistons are vertical if I recall correctly from the rebuild. I'll try anything at this point, just curious.
I don't know if I have an accurate explanation but what I was thinking at the time was to eliminate any air trapped in pockets or passages. Similar to adding coolant in a motor. Sometimes it helps to raise the front of a car or motorcycle to let the air escape while the coolant goes in. Also adding the liquid slowly will fill the pockets before trapping the air.
The only thing I know is it worked for me. Also, I figured out that pneumatic bleeder didn't help at all as it just sucked the fluid directly from the reservoir straight, out the bleeder nipple, never filling the caliper. So lots of hand pumping with the brake lever while holding the caliper horizontal was the only thing that got me any pressure. It took hundreds of miles of riding before all the air finally came out. I think a vibrating sander might help speed that up?
This may very well be why some people talk about a pressure bleeder instead of a vacuum bleeder. Hmmm
The only thing I know is it worked for me. Also, I figured out that pneumatic bleeder didn't help at all as it just sucked the fluid directly from the reservoir straight, out the bleeder nipple, never filling the caliper. So lots of hand pumping with the brake lever while holding the caliper horizontal was the only thing that got me any pressure. It took hundreds of miles of riding before all the air finally came out. I think a vibrating sander might help speed that up?
This may very well be why some people talk about a pressure bleeder instead of a vacuum bleeder. Hmmm
Another thought about this. The reason I had trouble getting pressure back is because I pushed the pistons all the way in to their seats, eliminating almost all fluid in the caliper. After getting back to full functioning pressure, I notice the firmness of the lever is much better than it was prior. So I have to assume that the fluid that came out of the caliper was old. How old, I don't know. Does the fluid in the caliper mix with new fluid when flushing the reservoir and lines?
I'm also thinking that gravity bleeding may be a thing. I've read about it but never tried it. It would make sense to have the caliper horizontal, setting with the inlet clocked 180 from the bleeder nipple, the bleeder is above, and they are vertical to each other. Open the bleeder, fill the reservoir and wait till fluid comes out. Just thinking out loud.
I'm also thinking that gravity bleeding may be a thing. I've read about it but never tried it. It would make sense to have the caliper horizontal, setting with the inlet clocked 180 from the bleeder nipple, the bleeder is above, and they are vertical to each other. Open the bleeder, fill the reservoir and wait till fluid comes out. Just thinking out loud.
Laker, You gave me an idea.
I think I know a simple way to supply pressure without the danger of introducing more air into the system.
I sent you a message.
Ride safe, Ted
I think I know a simple way to supply pressure without the danger of introducing more air into the system.
I sent you a message.
Ride safe, Ted
After some discussion with Ted on his ideas I came up with a new theory. Pressure bleeding from caliper should work but here is a different approach.
*After purging the caliper of all old fluid and with the caliper still bolted in place and very thin old pads in place, blow the pistons out with compressed air to full extension.
*Fill the caliper with fluid with a syringe through the intake port until it comes out the bleeder. Caliper is horizontal as in post 13. Close the bleeder. Reinstall the brake line. Bolt caliper back in place.
*Now pry the pistons about half way in towards fully seated, but don't push all the way in because that's what started the problem in the first place.
*This should effectively reverse pressure bleed the air out of the caliper.
*Finally bleed the reservoir and brake line with a vacuum bleeder.
*I'm sure there will be some air remaining but at least you should be able to get some pressure for future bleeding after vibration or riding.
I'll prove this out this winter. But worth a try now if you can't build any pressure.
*After purging the caliper of all old fluid and with the caliper still bolted in place and very thin old pads in place, blow the pistons out with compressed air to full extension.
*Fill the caliper with fluid with a syringe through the intake port until it comes out the bleeder. Caliper is horizontal as in post 13. Close the bleeder. Reinstall the brake line. Bolt caliper back in place.
*Now pry the pistons about half way in towards fully seated, but don't push all the way in because that's what started the problem in the first place.
*This should effectively reverse pressure bleed the air out of the caliper.
*Finally bleed the reservoir and brake line with a vacuum bleeder.
*I'm sure there will be some air remaining but at least you should be able to get some pressure for future bleeding after vibration or riding.
I'll prove this out this winter. But worth a try now if you can't build any pressure.
Here's an update on the original problem. I installed a master cylinder rebuild kit as many of you suggested. I wanted to wait a week or so to confirm, but the problem seems to be resolved. Brake lever is staying firm now over 1 week and counting. All I really needed was the new rubber seals that fit on the piston. I didn't install any of the other parts in the kit. (Too bad someone doesn't offer just the seals without all the other parts.) Thanks again for all your suggestions!