Brakes!!!!

[dspshemp]

OK, so now that the bike runs real well, it came time to review my stopping power. My front calipers would lock up almost every time I used them. I did the 'spooge hole' fix, didn't work. I replaced the master cylinder, lever and hose, all to no avail. I rebuilt both calipers twice (the second time with the help of a professional). I have bled, rebled and re-rebled the lines, and am now at your mercy. Does anyone either know what could be wrong, or does someone have an entire front brake system from a xs1100SG that they want to part with? Please let me know as I am almost at wits end. Thanks!!! RB

[newmaac]

You said that you replaced the master cylendar. Can we assume that you bought new parts? I know that it is not unusual to have to do the spooge hole thing more than once.
What does the lever feel like? Is the pressure building a little each time that you use it, until it just locks, or is it grabbing immediately?

I doubt that your problem is in the calipers, but if you find that to be the case, I think that I have an extra set.


Mike

[dspshemp]

Yes, I catually purchased a new master cylinder unit with the lever and all. The lever feels like it should, until you hold it, and it loses pressure. The calipers don't lock up any more, but they also don't build up enough pressure to keep the pads on the rotors. Any help would be appreciated!! Thanks. RB

[newmaac]

Hmmm, that's just about the opposite of the earlier dilema.
I am not a mechanic, mind you, but the "loss of pressure" description seems as though it would be either a small fluid leak, or you still have a trapped air bubble.
How are you bleeding the system? Doing the old "pump and realease" thing, or using a Mighty-Vac type aid?
With all the various banjo bolts in the front brake system, it is not hard to imagine missing a little air if you are not moving a fair amount of fluid through the system when you bleed it.
Good luck

[yuddy]

DSPSHEMP,
Where did you get the new master cylinder?
I have been looking for some time now with no luck.

[dspshemp]

I got an aftermarket one, after rebuilding mine with the Yamaha kit. I got it from the dealer who ordered it for me. I have since given up, and sent it to them. I rebuilt my entire head, cleaned my carbs, and everything is OK, but the brakes were the final straw. I now have two mechanics at the local dealer fed up as much as me with the brakes. They have tried everything they could think of. I think I need to order the factory setup from Yamaha. If anyone else has suggestions, I would be grateful!! Thanks!!

[Ken Talbot]

Going back to the first note, when you did the spooge hole fix:
- did you flush the system and install fresh fluid?
- just how ugly was the old fluid?
- with the cover off and carefully applying and releasing the brake, did you notice a little squirt of fluid up from the spooge hole?
- was the front end still locking up at this point?

[NOMAD]

I just went through the same thing with my '80 XS1100SG, the PO had put on a later model master cyl. with a 14mm bore. I tried everything until I figured out the bore was wrong. I found a used m/c off of a '79 XS750S ( 11/16" bore) and rebuilt it, all's fine now.

NOMAD

[dspshemp]

Nomad,
Thanks for the info!! I belive I was off about 2 mm on the bore. I have now ordered a new master cylinder off of another bike which is currently in production, and uses the same specs. Since this is a test, I will post the info as soon as I know it works. The price from Yamaha Direct was about $45. RB

[dspshemp]

Ken,
After the 'spooge hole' fix, I already had the calipers off and rebuilt. There is some backsplash from that hole, but still not enough pressure to hold the brakes. I guess at least they don't lock up any more!! They also don't stop me . I will keep trying, and posting until something works, to help someone out in the future. Thanks everyone!! RB

[NOMAD]

dspshemp,

I found that all the later models I checked out where 14MM, even the ones with dual front disc had smaller pistons in the calipers and used the smaller master cylinder. The 11/16" bore is about 3.5MM larger, and the only thing I found that used it was '78-81 XS stuff. It does'nt have to be an 1100, my dealer cross referenced the m/c kit and found it was used on 500s-1100s of that vintage. Like I said mine came off of an XS750S, he said I needed one off a special to be the right angle for the resevoir. This may not be a big problem since they seal up tight once the cover is on. We found that the bottom of the m/c was marked with a 14 or 11/16, hope this helps you out.

NOMAD

[Jerry]

FWIW....

I had a similar problem on a car once. Turned out I had installed one of the "cup" rubber seals backwards, and fluid was leaking back past it........JAT

[nashville_bill]

Is it blocked?

Just a thought. I wonder if somewhere in the process the brake line, or one of the connections, has become blocked, or partially blocked. When you open the bleed screw on a caliper, after pumping up the master cylinder, do you get a good volume of fluid?

[fusionking]

BRAKES!!!!!!!!

Back about '86 or so I rode a 80 midnight special. Ever once in a while when I'd use the front brakes I could feel 'em draggin'. I would then pull over & just loosen the bleeders one at a time. They would squirt out just a little & be fine. There was no real pattern to this symptom, just a little inconvieniant & embarassing so I lived with this mystery & sold the bike with it . Funny they never mentioned it! A few years later I had a auto parts/garage/machine shop business & started running across this same problem in cars & trucks only it would be just one wheel. Most people would try the caliper but it nearly always was the brake hose . Seems like they get a little "flap" in there & they let pressure thru but it won't let it back off. I always thought after that I must've had a problem with the upper hose on old blackie. Don't know if this might pertain you but it might just help some poor dude who's been pullin' his hair out!!!

[dspshemp]

Well, since I have no more hair to pull out, I have become fed up with my brakes (took me two months!!) Now that I believe the new m/c will work, to eliminate any other problems, I ordered my s/s brake lines just in case. I have replaced the lines, but not with s/s. We'll see. I'm keeping my fingers crossed.