Front brakes locking and smoking....HELP!

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rcollins · #1 Unread post by **rcollins** » Sun Aug 06, 2006 10:50 am

I've had my Yamaha XJ650 maxim for about a month now, and after collecting gear and getting comfortable with riding (finished MSF course as well) I was ready for my first long distance ride (~45 minutes to campground). After about 15 minutes I slowly began more and more aware of how fast the bike was slowing down, and it was just acting weird. Finally it got much worse and at a stoplight all the pieces came together when I saw smoke coming from the front caliper. I was in the middle lane so I needed to cross the rather large intersection to get to a parking lot. When I tried to launch I stalled it cause of the brakes, then restarted and dumped the clutch at like 4 grand to get it moving and into a parking lot.

After it sat for a while the brakes ended up loosening up and I drove it home just using the rear brake for fear of a re-occurance.

What could this be? I took off the pads and caliper and didn't see much, except they are old and gummy. My inclination is that the caliper is just bad, but I'm not sure. Any help would be greatly appreciated, I'm trying to avoid taking it in and paying an arm and a leg for something I can do myself. Below are some pictures.

Gadjet · #2 Unread post by **Gadjet** » Sun Aug 06, 2006 12:03 pm

*edited the above post to make the pics work*

Looks and sounds to me as if your brake pads were rubbing on the disc, transferring frictional heat to the brake fluid - when the brake fluid heated up, it expanded and exerted more pressure on the brake pads, yada yada yada.

Get yourself a shop manual for your bike and a rebuild kit for your front caliper, then pull it apart, clean it and rebuild it. I would also recommend changing your front brake pads at the same time.

This is a job that you can do yourself with a few tools, a modicum of mechanical skill (the ability to follow the instructions in the manual help) and some time.

if you aren't comfortable doing this, then you can take the caliper itself to a shop and have them do it.

Shorts · #3 Unread post by **Shorts** » Sun Aug 06, 2006 12:14 pm

Ohh, brakes, my most recent nemesis

+1 above. A rebuild sounds to be in order as the calipers are sticking.

Before you open up the hydraulic line, cover the wheel, tire and whatever else you can with some aluminum foil. If you put it on your fender, be sure you lay a towel between the foil and paint. Get vinyl tubing to fit on the bleed screw. I'm sure you know this, just reiterating, you don't wanna get hydraulic fluid on paint and be sure to clean the rotor with brake when you're done cleaner.

sharpmagna · Sun Aug 06, 2006 2:18 pm

How does the brake fluid look? I had something similar happen to me on my bike. I had just bought it from a guy at work and I had ridden it for a few days. When I went to pull it out for a ride at night, the bike wouldn't budge. The front brakes had locked shut on the front rotor.

The next day I pull the caliper and notice rust on the outside of the pistons. I cleaned them with some scotchbrite pads but the pistons wouldn't retract. I opened up the brake master cylinder and it looked like warm chocolate ice cream (YIKES!!!). Since brake fluid is suppose to be clear, I knew this bike had not had the brake fluid serviced in a long time. I drained the fluid and cleaned out the brake master cylinder with q-tips. I then flushed some new clean fluid through the lines and then bled the brakes. The caliper and pistons worked fine after that and I've enjoyed 4k miles on them since.

I'd verify the brake fluid before you go rebuilding your caliper. It's the cheaper and faster fix.

rcollins · #5 Unread post by **rcollins** » Mon Aug 07, 2006 3:22 am

Does a rebuilt kit include taking the piston out? I've heard that can be a huge headache. Also where's the best place to get a kit...just a Yamaha dealer?

Thanks for the help.

sharpmagna · Mon Aug 07, 2006 4:10 am

It probably will require taking the piston out. There are some o-rings there that the piston slides against. I didn't need to do it, but my service manual mentioned a method to get the pist out. If you have an air compressor, bet the blowing attachment and blow some compressed air into the open bleeder screw hole. Have a towel or something ready to catch the piston as the air will push the piston out. Not sure if this is possible with your caliper, but worth a shot...

Yeah your local yamaha dealership would probably be able to order you a rebuild kit. It is probably something they don't normally stock.

CORSCO · #7 Unread post by **CORSCO** » Mon Aug 07, 2006 5:31 am

Make sure the return orifice in the master cylinder is clear. It will be the small hole just after the plunger from the lever. If this is clogged, fluid will not return to the master cylinder causing the brakes to lock up after a few times.

Pull in the brake lever and make sure you see a squirt of fluid escape the hole. Most master cylinders have a cover over the hole. Just make sure you do not splash it all over you paint.

roscowgo · #8 Unread post by **roscowgo** » Mon Aug 07, 2006 9:14 am

+check to make sure you arent getting any other fluids on your rotors. fork oil, brake fluid etc.

rcollins · #9 Unread post by **rcollins** » Sun Aug 13, 2006 4:51 pm

Well this weekend I finally had some time for the bike, and dug into the brakes. I polished up all the components, new brake pads, and thought things were going smoothly until I tried to bleed the system. I was using the old fashioned way of opening the bleeder (with the hose coming out and in brake fluid) then holding the brake, closing the bleeder, and then letting go of the brake which should suck fluid in to the system from the resevoir.

The problem is it wasn't taking anything! No matter what I tried, it would not take any fluid from the resevoir. What's odd is I know the piston is working because when I would open the bleeder it would suck up fluid from the soup can I had the hose in...meaning there was the negative pressure in the system. Does anyone have any idea why this would happen?

Gadjet · #10 Unread post by **Gadjet** » Sun Aug 13, 2006 5:06 pm

to get the fluid to come out of the bleeder, you need to squeeze the brake lever. this pushes fluid from the master cylinder, through the lines and to the brakes.

if you are closing the bleeder, applying pressure, then releasing the lever while opening the bleeder, you are going to suck air into the system.

you want to push the old fluid out of the lines and into your catch can through the bleeder while making sure that the fluid level in the resevoir doesn't drop too low to allow more air in.