K7 750- Front brakes not disengaging after stops - GSXR.com
 
LinkBack Thread Tools Display Modes
post #1 of 14 (permalink) Old 08-04-2013, 08:58 AM Thread Starter
Novice
 
Join Date: Apr 2008
Posts: 34
K7 750- Front brakes not disengaging after stops

I've developed some weird issue this year and looking for recommendations.
So I have a low mileage K7 750, about 4,000 miles
Didn't get ridden last year because of extensive OCONUS travel.

Fluid is as clean as it gets.

So the issue is; When riding I can use the front brakes a few times over the span of say 1/2 mile and then the front brakes will not disengage. They'll slowly start gripping until its just locked onto the rotor. I'm then forced to bleed a little bit of the brakes to release pressure. No bubbles.
Saturday and then this morning I took the calipers off to inspect. Nothing popping out.

From what i can decipher the fluid is coming down the line when engaging, but is not making its way back up when the handle is released. I had no issues taking the pads out on the left side and moving the pistons back and forth, I was able to do the same on the right side. But at the same time I can't seem to get all the pistons to move back in, in order to place the pads back in.

So I'm speculating that their may be an issue some where from the caliper going back up the line to the handle.

I'm a little stumped at this moment as to the issue or next steps.

Other facts, I did replace the stock handles with aftermarket units.




Last edited by Nichepi; 08-04-2013 at 09:48 AM.
Nichepi is offline  
Sponsored Links
Advertisement
 
post #2 of 14 (permalink) Old 08-04-2013, 09:39 AM
C3K
Lifetime Premium
 
C3K's Avatar
 
Join Date: May 2010
Location: AL
Posts: 4,112
Sounds like the caliper is sticking. have you cleaned the calipers? I used plain dish soap, water and a baby tooth brush and thoroughly cleaned each piston on each caliper. The build up on the pistons will limit the travel and cause them to stick.



Quote:
Originally Posted by OUTINFRONT View Post
You ain't got a chance in hell good luck.
C3K is offline  
post #3 of 14 (permalink) Old 08-04-2013, 09:47 AM Thread Starter
Novice
 
Join Date: Apr 2008
Posts: 34
yes I did, brake cleaner and several other products.
I posted some additional pictures.

Additionally based on your statement, I had gone back and was able to push the pistons individually back and forth with no major effort. The issue appears to be pressure buildup. Where fluid is not getting sent back up the line.

Last edited by Nichepi; 08-04-2013 at 09:51 AM.
Nichepi is offline  
Sponsored Links
Advertisement
 
post #4 of 14 (permalink) Old 08-04-2013, 09:55 AM
Racer
 
Join Date: Dec 2009
Posts: 924
It sounds more like you have a plugged compensation port in your master cylinder. There is a small hole in the master cylinder piston that allows fluid to return to the resivour from heat expansion. The first part of the piston movement covers that port to let pressure build. When released, the piston retracts, and opens the small port. You need to remove and clean your master cylinder, paying attention to the compensation port. They really aren't that hard to dissemble, usually only needing a pair of circlip pliers. It's a common problem on bikes that have been sitting. Another possibility is that your lever is holding the piston in a partially engaged position. If you are using aftermarket or non-stock levers, go back to stock, as many of those don't fit properly and cause that problem.
bobl is offline  
post #5 of 14 (permalink) Old 08-04-2013, 09:57 AM Thread Starter
Novice
 
Join Date: Apr 2008
Posts: 34
Thank you those sound like good recommendations, I'll start looking into that.
Nichepi is offline  
post #6 of 14 (permalink) Old 08-04-2013, 10:00 AM
C3K
Lifetime Premium
 
C3K's Avatar
 
Join Date: May 2010
Location: AL
Posts: 4,112
Quote:
Originally Posted by Nichepi View Post
yes I did, brake cleaner and several other products.
I posted some additional pictures.

Additionally based on your statement, I had gone back and was able to push the pistons individually back and forth with no major effort. The issue appears to be pressure buildup. Where fluid is not getting sent back up the line.
Is the lever sticking? I can only think of a few issues it could be. Sticking calipers, sticking lever or MC piston not traveling properly to allow fluid to come back to the MC



Quote:
Originally Posted by OUTINFRONT View Post
You ain't got a chance in hell good luck.
C3K is offline  
post #7 of 14 (permalink) Old 08-04-2013, 10:09 AM
Lifetime Premium
 
rv6john's Avatar
 
Join Date: Mar 2013
Location: In the twisties around Hendersonville, NC
Posts: 7,767
Quote:
Originally Posted by Nichepi View Post
IOther facts, I did replace the stock handles with aftermarket units.
This is your problem.

Either the pin that presses the master cylinder piston is not seated properly or the aftermarket lever is causing a problem.

What is happening is that the master cylinder piston is not moving all the way out (opposite pushed in) to open the port into the reservoir. Fluid is trapped and as you use the brakes it heats, expands and causes the brakes to grip even more. There have been some serious crashes due to this. Just imagine grabbing the front brake at 60 mph as hard as you can.

Pull the lever off and make sure the pin is in the center of the piston and is fully seated in the hole in the lever. You might be able to adjust your lever, but don't know what you have.

When you re-install the lever, it should not take any pressure to align the pivot bolt. If you have to push to get it to align, you are pushing in the master cylinder piston causing the problem.
rv6john is offline  
post #8 of 14 (permalink) Old 08-04-2013, 10:36 AM Thread Starter
Novice
 
Join Date: Apr 2008
Posts: 34
Yes, by recognizing the issue right off the bat I was able to slowly ride around the neighborhood to diagnose before jumping onto the freeway.
Nichepi is offline  
post #9 of 14 (permalink) Old 08-04-2013, 11:07 AM
Pro Racer
 
josjera's Avatar
 
Join Date: May 2011
Location: Central Jersey
Posts: 5,189
Why would aftermarket levers make only half the pistons engage?

2011 GSX-R 750L1
Quote:
Originally Posted by Kimbroly View Post
hey darth has a mouth.. he just has to reach awkwardly under his helmet.... don't you star wars?
josjera is offline  
post #10 of 14 (permalink) Old 08-04-2013, 11:16 AM
Pro Racer
 
95 imp 5.7ss 05specV 06k6's Avatar
 
Join Date: Aug 2012
Location: VA
Posts: 1,091
Quote:
Originally Posted by rv6john View Post
This is your problem.

Either the pin that presses the master cylinder piston is not seated properly or the aftermarket lever is causing a problem.

What is happening is that the master cylinder piston is not moving all the way out (opposite pushed in) to open the port into the reservoir. Fluid is trapped and as you use the brakes it heats, expands and causes the brakes to grip even more. There have been some serious crashes due to this. Just imagine grabbing the front brake at 60 mph as hard as you can.

Pull the lever off and make sure the pin is in the center of the piston and is fully seated in the hole in the lever. You might be able to adjust your lever, but don't know what you have.

When you re-install the lever, it should not take any pressure to align the pivot bolt. If you have to push to get it to align, you are pushing in the master cylinder piston causing the problem.
+1 when I bought my after market levers I read about people having this problem. I drilled out the hole in the brake lever a little deeper and wider just to make sure the plunger from the MC is not constantly being held in.

Quote:
Originally Posted by JohnPaul View Post
I'm so enlightened I just shit and fell back in it..
When your front wheel starts skipping on throttle roll on........not 600 problems, you got 1000 problems
95 imp 5.7ss 05specV 06k6 is offline  
post #11 of 14 (permalink) Old 08-04-2013, 11:29 AM
Pro Racer
 
josjera's Avatar
 
Join Date: May 2011
Location: Central Jersey
Posts: 5,189
are you guys getting cheap china knockoff levers and having to mod them? Or are you paying the money for name brands and having this issue as well?

I only ask because this is the first time I've seen this issue on here, and I personally have Pazzo, and they work great. Just trying to get some understanding on the theory of operation here.

2011 GSX-R 750L1
Quote:
Originally Posted by Kimbroly View Post
hey darth has a mouth.. he just has to reach awkwardly under his helmet.... don't you star wars?
josjera is offline  
post #12 of 14 (permalink) Old 08-04-2013, 11:50 AM Thread Starter
Novice
 
Join Date: Apr 2008
Posts: 34
So I believe I found the final issue which can be contributed to a about 50% lack of clear directions in the product install and 50% personal stupidity.

Once I taken the aftermarket lever off I could definitely tell the plunger was crooked. So cool. Repositioned it inside the lever and went for a few laps around the block. In the past I only made it about 3 or 4 times before it froze up. I made it about 10 before heading back and the issue hit again.

First I blamed Obama.. Seemed like the logical thing to do.

Then I removed the Lever to reposition again, then realized that inside the pit was a brass fitting. Now previously this fitting was turned backwards so i never noticed the indentation. But by cursing Obama the Motorcycle god presented me with a gift.
I then realized that the plunger was meant to go inside this little brass indentation to maintain alignment. Again seems logical.

In this picture you can see to the left side the brass fitting inside the pit. I went back to look at the directions and it never mentioned anything about alignment with this brass fitting.


Nichepi is offline  
post #13 of 14 (permalink) Old 08-04-2013, 11:51 AM
Lifetime Premium
 
rv6john's Avatar
 
Join Date: Mar 2013
Location: In the twisties around Hendersonville, NC
Posts: 7,767
A picture is worth a thousand words. Credit to someone else that drew this. I just stole it off the internet.

The port where the rubber hose connects must be open when the brakes are released.

This is why disc brakes also do not need adjustment. Each time you use the brakes the fluid is either added or vented as needed.
Attached Thumbnails
Master cylinder drawing w label.jpg  
rv6john is offline  
post #14 of 14 (permalink) Old 08-04-2013, 01:04 PM
Novice
 
cody0789's Avatar
 
Join Date: Aug 2013
Location: Michigan
Posts: 25
I had a similar problem on my bandit.
. There is a pin hole In the master cylinder that ended up being clogged!

Sent from Motorcycle.com Free App
cody0789 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the GSXR.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
Squeaking noise after disengaging kill switch Staygold Tech and performance chat. 6 03-21-2014 02:02 PM
97 gsxr 750 high rpm when disengaging clutch joeg473 Tech and performance chat. 11 01-28-2014 07:49 PM
k7 600 stops revving at 11k rpms climber90 Tech and performance chat. 2 05-09-2013 06:48 PM
GSXR 400 stops after .5 hr desm0 Tech and performance chat. 0 03-08-2012 08:33 PM
starts but stops after adjusting tps codes c32 2 35 HERES A HARDBALL TONYTEE71 Tech and performance chat. 3 11-25-2010 08:29 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome