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Brake symptoms - what are they trying to tell me?

  • Thread starter Thread starter Barneycanoe
  • Start date Start date
B

Barneycanoe

Guest
Wondering if you have ever had brakes that feel like this?
\
1982 GS850GL, 48000kms. Recently bled the brakes until I got only fresh fluid coming out. May have gotten rid of a few air bubbles - not sure.

Brakes work ok, but what is happening is:

initial pull on lever, nice firm application of brakes, good feel, etc.

then lever will come in another 1/4" or so toward the handlebar.

Almost feels like two-stage brakes. Braking force does not change throughout, just the lever is initially stiff, then relaxes about 1/4" more. Then it is quite stiff.

I'm thinking it's the original brake lines as I see a very small amount of movement in the lines upon application of the brakes. What's your take?

Dave

Ontario, Canada
 
Sounds like you need a rebuild kit for the master cylinder.

If you had any air in the system, it would not have gotten hard the first time, then released and gotten hard again.

.
 
Could be the master cylinder has pitting in the metal surface so when the piston gets to the damaged part the fluid just bleeds around the seal. I'd take the master apart, and look inside with a flashlight after you clean it up - if there are any pitts in the metal the master needs to be replaced.
 
Sounds like air in the lines and or some gunge in the master cyclinder.

Has the master been dissassembled and cleaned anytime recently? If the bike has sat for any length of time, the whole system should be thoroughly cleaned, calipers, hoses and the master.

With older (original?) hoses you usually get a spongy feel so it doesn't sound like they are the problem but over time they can develope pin holes that let in air. I'd junk the hoses and replace them with kevlar lined stainless steel braided anyway. Brake feel with these lines is greatly enhanced...well worth doing.

If the calipers haven't been cleaned, they shouild also be looked at as they are prone to dirt and water infiltration if seals wear or break down. The biggest issue is that rust can form in the bores of the caliper pistons and it can attack the piston itself, breaking down the chroming and causing pits and fissures. Over time the pitting can lead to more rust forming and it can jam a piston in the bore. Very serious. A cleaning and rebuild seal kit every 4 or 5 years is good preventative maintenance.

You can't afford to be loosie goosie with brakes just remember your life can depend on them.

Give everything a good cleaning and then see how things work.

cheers,
Spyug
 
Looks like I have some work to do...
 
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It seems like a big deal but really isn't.

The biggest problem could be getting the piston out of the caliper if it is gunged up ( don't you just love technical terms?). The easiest thing to do is take the caliper off of the fork leg but still connected to the hose. Remove the pads, pins and anti rattle clips etc.Suspended it in a large plastic bucket and bump the lever'til they shoot out. You might want to put a piece of scrap wood over the top of the bucket to stop the piston from beaning you. It will come out witha bit of force.

Once you have it out , you can remove the caliper from the hose to work on. Dollars to donuts there will be crap in the caliper. Maybe rust on the bore wall and the piston skirt.

Carefully clean up the rust/crude. I use dental picks and fine steel wool. Remember to only use fresh brake fluid for cleaning.....no other solvents as these can have bad reactions with the fresh fluid when things reassembled. Also remember that brake juice is a great paint remover so you may have to repaint the caliper if it gets touched.

Now with the piston. If there is rust on the crown and or down to the seal don't worry just clean it. Make sure the seal groove is clean too or the new seal won't seat properly. Any rust, pitting or cracking of the chrome on the skirt ( i.e. the bore area) and the piston should be replaced. Once the chrome is compromised then rust will always form and as mentioned the piston can be made to jamb. For around $30 for a new piston it is not worth taking the chance in my mind.

Seal and dust kits are still readily available, as are kits for the masters. Either from Zuk retailers or on line like Z1 Enterprises or the like. If you have a local bike wrench they can usually get them for you through Parts Canada also. Stainless steel lines can also be made up locally or you can get the parts and DYI...not hard either and lots of info on line ( even you tube vids). DYI should save some cash.

Once you have a refreshed brake system you will feel a world of difference. With the SS lines especially, two finger stops ( even emergencies) are kids play. Really well worth doing.

Anyway, get to it and let us know how it goes.

Cheers,
Spyug
 
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Thanks - and an excellent time-saving tip from my wife!!

Thanks - and an excellent time-saving tip from my wife!!

Thank you for your responses. I have cleaned out brakes before but I never felt this peculiar feeling, and it seems to me it didn't do it last sumer.

I think Nessism may be right, now that I've had everything apart. There is some pitting in the bore of the master cylinder. Actual piston cup and seals were slightly mangled at one point. I'm going to reassemble while I source another master cylinder - I did put in a new piston/cup/seal kit. The system has obviously been sitting for a while - here's two pics of the gunge.

Now for my wife's excellent tip!
The last master cylinder I took apart on my 1979 CB650, I was wrestling with the circlip for close to an hour, trying to get it out with an inadequate pair of circlip pliers. Patiently I worked away, but obviously my frustration was showing because my wife came over to see what I was struggling with.

She turned to my toolbench, picked up the implement shown which I got in a screwdriver kit from Canadian Tire, and said, why don't you use this to winkle it out. First try, out it popped!

Now the Suzuki circlip is considerably stronger - but it also came out without hardly any trouble.

That's her tip, highly recommended. Just put some rust or gunk loosener in for a while if needed, pull one of the hole ends round to the front, and lift away.

Dave
 
Tip Picture

Tip Picture

See the tool my wife gave me to get the circlip off
 
Okay, I need a new master cylinder. I realized (Finally!) what was happening.

When I pull the brake lever hard, it feels solid. When I give it a lesser pull (like when slowing for an intersection turn) the lever travels farther.

This is due to the pitting - the hard pull expands the cup and seals the bore of the MC. The lesser pull allows fluid to escape over the edge of the cup via the pitting.

They don't make the master cylinder for the 82 GS850GL anymore. Nessism, I believe you said in another thread that any 5/8" MC bore will work. Does it have to be a Suzuki one?

Can anyone confirm. Does anyone know definitely what will replacce the original part?

Cheers
 
The only other criteria to be concerned with is that it will accept a 10mm banjo bolt, and that it is designed to work with the same brake fluid.
 
Got a master cylinder body for $20 from a local wrecker. Piston was seized but for $20 I was willing to take a chance.
Got it home, gave it some liquid wrench, got the piston out, and it did have some pitting, but surface only, rough pebbly looking.

Put it on the bike, bled the brakes, WHOOPPEE!

I now have front brakes that work.
 
Barneycanoe said:
Okay, I need a new master cylinder. I realized (Finally!) what was happening.

When I pull the brake lever hard, it feels solid. When I give it a lesser pull (like when slowing for an intersection turn) the lever travels farther.

This is due to the pitting - the hard pull expands the cup and seals the bore of the MC. The lesser pull allows fluid to escape over the edge of the cup via the pitting.

They don't make the master cylinder for the 82 GS850GL anymore. Nessism, I believe you said in another thread that any 5/8" MC bore will work. Does it have to be a Suzuki one?

Can anyone confirm. Does anyone know definitely what will replacce the original part?

Cheers
Click to expand...


I put a master off a Bandit 1200 on mine, seems to work, but the brake lever is different to activate the brake switch.
 
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