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Pump-action front brake

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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I replaced the brake fluid in my front brake today, and with the help of a friend got the bleeding done according to the rule of thumb (left antidive,left caliper,right antidive,right caliper). We double checked all four units, and were unable to get any more air out.

However, I can almost pull the lever to the handle on the first pull - on the second it's right where I want it. Is this normal ? We tried real hard but couldn't get any more air bubbles out of the system, as far as I can tell it should be air-free. :?
 
the anti-dive system is known to be very dificult to bleed,that is often the reason why people disconnect the anti-dive, it stems from the way the brake lines are run.
 
I disconnected (but didn't remove) the anti-dive today and re-bled the brakes. Still it's not what I want - I can almost pull the lever to the handle on the first pull. But I can't for the life of me squeeze any more air out of the bleed nipples. :x

Is there some secret air pocket I don't know about ? :?

Oh and - removing the anti-dive did make a noticable difference, the bike really does dive a lot more now.


edit: I have not serviced the master cylinder since I bought the bike (this winter)
 
D|sElMiNk said:
I have not serviced the master cylinder since I bought the bike (this winter)
Click to expand...

And I'll bet that's where part of your problem is ... you have fluid bleeding by the master cyclinder as you compress the lever. 8)
 
Air can get trapped at the point where the banjo bolts to the master cylinder if the master cylinder is angled upward so that the banjo is higher then the cylinder itself.
Unbolt it from the bar, angle it downward and slowly work the lever, any trapped air will work its way into the resevoir.

bill
 
Thanks billp - I'll try that first thing tomorrow. I did notice that the banjo on the master cylinder pointed straight ahead or slightly upwards - hopefully that is all there is to it. :)

If not I'll get the parts needed and fix this thing the hard way. :roll:

Shaftzuki : I sure hope you're not right :wink:
 
I think you need to bleed the master atleast... What I mean is compress it and loosen the banjo so air/fluid comes out and tighten it off before it reaches bottom, just like bleeding the bleeder bolts. I bleed all my banjos if I open the system, but there is a good chance your master cylinder doesn't seal properly. A good junk yard will have one cheap with some form of guarantee, but you may just want to spend a little extra and get a new one if you have the money.
 
another item to look at is the brake lines themself, some experts say to change the lines every couple of years.
the standard brakelines do get soft and will expand under presure when they get old, causing a mushy lever.
I have braded steel lines on my bike and can tell a huge differance when compaired with a bike with standard rubber lines.
 
Bleed all banjo bolts like they were bleeders, pump hold and crack open the banjos. Especially the stupid junction box on the lower triple.

Hand vaccuum pump I bought was the best $60 I ever spent. Keep at it, you will get it eventually.

A modern day 90ish GSXR master cylinder, removal of the junction box, and a set of braided lines can make an unbelievable difference in braking and feel.

Hope this helps,

8) Andre 8)
 
Okay, I'll go over the banjos as well as soon as I have the time. If the brakes are good after doing that I'll let it be. If not I'll order all the parts needed to service the master cylinder.

I have contemplated the idea of removing the junction box and instead using a double banjo on the master cylinder, but that would mean getting new brake hoses - and I don't want anything less than what I've got now (looks like woven steel).

And as for the GSXR stuff, I'd like to exchange the whole front end when time and money allows. :twisted:
 
Don't waste time and the expense of extensive modifications- the stock master cylinder and brakes on this motorcycle are more than adequite for street riding. First, get rid of the anti-dive system-remove and blank off the units with easily fabricated 1/4 inch aluminum plates(use the stock units for templates). Second, stiffen up fork springs with preload adjusters or spacers. Third, add a fork brace and use good quality rubber up front. With the braided steel lines you already have installed two fingers on the front brakes will approach the limits of braking for street riding. How do I know this- I have had the above mentioned setup on my 83'750ED for the past 15+ years and 40000 miles. If you ride hard enough on the street to overcome the braking capabilities of this setup, you need to increase your life insurance. Ride On, Ed.
 
For the price of rebuilding the front master cylinder, you can get a GXR master, finger length adjustable lever, brake switch, and resevoir and cap. I got the complete assembly off of ebay for $15.50 US. The master is the weak part on the GS, the pump stroke is way to long. As for the antidives, they work fine. Remove the top part of the antidive unit and make sure the plunger moves freely up and down, and they will work properly. I agree if you remove the antidives and get different springs or put in spacers it will compensate for the antidive units. But if you do this and leave the antidives on it will be even better. I get about an inch of travel with two fingers to bring me close to a full wheel lockup and the front end just drops a couple of inches. Also go to a 20 weight fork oil, this will help also.

Hope this helps,

8) Andre 8)
 
The problem you are describing is due to the antidive units not the master cylinder. These units require too much plumbing and use brake pressure to activate. Why not use springs to control dive and channel all available brake pressure where it is needed-the calipers? Antidive was an 80's fad that has gone away because it offered no real benefit. You will be surprised at the amount of pressure you recover by removing these units and and their plumbing. It is simple fluid dynamics- it takes greater pressure to push a fluid over a longer distance. Ride On, Ed.
 
The problem isn't the anti-dives, as they have been disconnected for the last two bleeding sessions. I treated the banjo on the master cylinder to a bleeding session today, haven't touched the banjos on the splitter. No improvement :(

I had just as good brakes with the anti-dives as I have now - so I'll probably hook them back up later. And you are right oldschoolGS, the brakes on this bike are good enough - all I really want is to have the brakes ready at any time. With the way the front brake is right now I ride very defensively, which might not be such a bad thing, but I still want proper braking potential! :evil:

motorcyclemodeller : I'll look into pricing on GSXR parts from wrecked bikes - and compare it to the cost of the parts I'd have to buy to service my stock brakes.
 
I would not ride at all until you sort out your problem. I was simply stating that if you disconnect the antidive units you will get better brake response provided all other brake components are properly working. If you cannot bleed the brakes completly with or without the antidive connected, you have a master cylinder, bleed fitting or line problem. Just out of curosity, when you disconnected the antidive units did you remove the lines that ran to the antidive units and only left connected caliper lines? I don't remember but I believe you will need to use the shorter banjo bolts from the dive units to connect the calipers as you should only now have a single brake line run to each caliper. Hope this helps, Ed.
 
It is obvious then that the master cylinder is at fault. And yes, I used the short banjo bolts that used to sit on the anti-dives instead of the double-length bolt. I put the double-length bolts on the antidives, just so I wouldn't lose them (and also try to stop the anti-dives from being clogged with dirt).

motorcyclemodeller : is there a specific year you recommend, or rather a choice of good years ? And as for GSXR600/750/1100 - is it the same pump ?
 
If you have access to a parts house that can order K&L stuff - you can re-build your original for about $25 US (not sure what the conversion works out to) ... Or you can order original Suzuki, although they are quite pricey!! 8)
 
I decided to reconnect the anti-dive today, so that I might be able to ride a little even with the scratch on the fork leg. Since I was gonna lose most of the brake fluid anyway I decided to undo all the banjo bolts and re-tighten them.

Got a friend of mine to work the brake lever while I aired out the brake calipers and anti-dive units. My friend pumped like crazy, building up extreme pressure before I opened the airscrews. When we were done the brake lever felt like it could stop a blackbird (and I mean the spy-plane, not the bike!) 8O

Being mighty proud of myself (and my good friend) since the front brake was now FINALLY working without pumping we both set out to take it for a test ride. About a mile from home the bike started to slow down drastically, felt like the engine had died. I was thinking WTH before I came to a halt at the side of the road. The front brakes had just locked up :? If someone could explain this to me I would be grateful.

Anyway, I opened up each of the four air screws one by one to let off some pressure - and voila - back on the road with a working front brake. Just using the index finger on the lever is enough to stop the bike when making any kind of stop except emergency braking.

The anti-dives don't work though. Strange. When I got the bike the anti-dives seemed to work just like they should, I was unable to push the front down when I applied pressure to the front brake lever. Now it's like the anti-dive isn't even connected.

Oh well - guess I'll just invest in some better (stiffer) springs and go up on the weight of the fork oil. I'm just happy I can finally stop the bike properly whenever I want :D
 
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