748 brake problem

blake748 · 03-15-2005, 12:04 PM

Need some help

got a '99 748 and the brakes decided to go on vacation. The back is almost not fuctional at all and the front is spongy (not air in the lines spongy) they just don't grab like they used to. Both problems seemed to happen at the same time. There is a little travel before the front starts to grab hard.
I've bled both ends to check for air, and the problem didn't change, I've checked brake pads and both are in good shape as far as thickness of pad and rotor wear.
I think the back master cylinder/pump (what ever its called) went out, when bleeding they hardly pushed any fluid but the front is killing me.

No its not Japanese!

yellowduc · 03-15-2005, 05:56 PM

Sorry it has taken a while for me to reply to this, I have never had the same problem and I'm not sure where you should look but you should become a member at http://www.ducati.net/ (sign up for the list and post the question), someone on there will help you out.

harm_ · 03-17-2005, 03:49 PM

change oil

asujosh1 · 03-23-2005, 08:49 PM

i have done some research because my rear brake sucks too, and apparently they are made so that they dont grab enough to lock up the rear wheel. i think that sucks, but my rear brake doesnt work woth a crap anyway..

FryDaddy · 03-24-2005, 03:18 PM

Maybe you need a new master cylinder for the front and back.
Change the old brake fluids and replace with new.
The brake pads could be worn down.
The rotors could be bent / warped or wore out.
Could be in your head.

But I have noticed that when I used to bleed my brakes on my other bike, they didn't seem as strong for some odd reason. For the back brake, It seems to me that most of all bikes you have to mash hard to get them to lock up when going at speed.

blake748 · 03-24-2005, 11:04 PM

I'm almost positive my back master cylinder is not working and needs to be replaced. I'm going to change the fluid in the front and go from there.

Thanks for your imput and keep coming with the ideas.

FryDaddy · 03-25-2005, 08:03 AM

Really, I have no idea of what it could be. Just change the rear mc and go from there.

jim schmidt · 03-25-2005, 08:15 AM

The chances of both brake systems failing at the same time are infinitesmal. Work on one system at a time. Forget the backs for now. It seems as though you have a bad master cylinder (which should be rebuildable.) Is it possible that you only noticed the back brake "problem" because the fronts went? Back brakes only account for a small fraction of the braking, 25% roughly. It will seem like your bike takes forever to stop.

One question: Did this problem arise after you bled the brakes or changed the fluid or pads or lines?

asujosh1 · 03-25-2005, 08:16 AM

before you go wasting your money on a new MC, read these threads, you will find them informative:

http://www.ducati.ms/ubbthreads/show...=&view=&sb=&o=

http://www.ducati.ms/ubbthreads/show...=&view=&sb=&o=

FryDaddy · 03-25-2005, 12:41 PM

Quote:

Originally Posted by jim schmidt

The chances of both brake systems failing at the same time are infinitesmal.

That saying reminds me of something that happend to me a few years back in 1999. The motorcycle learners book says that if your throttle gets stuck, stay calm and pull in the clutch. So I thought, "what if the throttle gets stuck and the clutch goes out at the same time also". I said, the chances of that happening is one in a million. So, one day I was riding my 1989 zx600 ninja (first bike) and I knew it was time to replace the clutch so I said I'm going to go ride about 4-5 miles and then put it in the shop until they can fix it. On the way back to my appartment, I stop at a stop light and pull the clutch all the way in and the bike is still moving slightly. Then I leave the light and twist the throttle and the throttle gets stuck open - I say what the hell. So now I have a stuck throttle and no clutch and this piece of s%*t is not stopping. I grab the brakes and ride them (so the speed of the bike would not get too high) until I can find somewhere to pull over out of traffic, I see a little garage and hit the brakes even harder. When I pull into the parking lot, theres loose rocks/sand and the back tire just spins and slings the bike from under me (I didn't fall or anything, just the bike). I touch the front rotors and the are like a frying pan, totally roasted. Man, I miss that bike, those were the times.

After that I had someone to take me back to my appt and get myself a

Point of the story, get the brakes checked to be on the safe side. Never know when you may be that one out of a million.

blake748 · 03-25-2005, 06:08 PM

The back is not that big of a deal right now. They do not work at all, however. If your stopped and push the back brake down you can easily roll the bike without any engine help.

The front problem started before bleeding the brakes, thats why I bled them. They are not at the "unsafe" point, they just are weaker than they used to be and the amount of lever pull to get a strong grab is too long.

jim schmidt · 03-25-2005, 06:26 PM

Quote:

Originally Posted by blake748

The back is not that big of a deal right now. They do not work at all, however. If your stopped and push the back brake down you can easily roll the bike without any engine help.

The front problem started before bleeding the brakes, thats why I bled them. They are not at the "unsafe" point, they just are weaker than they used to be and the amount of lever pull to get a strong grab is too long.

Oh. Look for glazed pads.

asujosh1 · 03-26-2005, 12:51 AM

i'm with him, take out the front pads and put some sandpaper on a nice very flat surface. you can use the sandpaper to rough up the pads, and then go through the manufacturers recommended break in cycle, and your pads will last a bit longer.

we used to do this at the track when we didnt have replacement pads, and our got all glazed over. it woks for a while, but i would be looking on eBay for a good deal in the interim.

blake748 · 03-31-2005, 09:04 AM

I've been crazy busy and haven't had a chance to mess with or ride my bike much until yesterday. I think were on the right track with the glazed pads. It only on one of my front rotors but I think that's it, they squeak just a little when lightly braking.

While I'm at it I'm going to change my brake fluid since its so easy to keep it of my painted body work

Thanks for all the info, I'll let you know the status when I find out what works.

blake748 · 04-02-2005, 04:24 PM

Front pads were glazed and was an easy fix once I had time to look and sand them down.

The back however is not going to be as easy or cheap. The master cylinder has to go!