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gs750es brake problems

  • Thread starter Thread starter hardley davidson
  • Start date Start date
H

hardley davidson

Guest
this is driving me nuts!!!!! I recently purchased a non running long sitting 83 gs750es ive been redoing everything and just have the front brakes left. i can build up pressure with several pumps of the brake but if i lay off for a second while it dosent lose ALL pressure theres a noticable loss and while test riding the brakes are weak and inneficient.

Ive rebuilt the master cylinder
dissassembled and cleaned out both calipers twice
checked all the lines and connections for leaks and havent found any
bled the system going on seven times in the correct sequence including alternating bleeding the master cylinder itself.
what am I missing!?!?!?!?!?!?!?!
 
hardley davidson said:
this is driving me nuts!!!!! I recently purchased a non running long sitting 83 gs750es ive been redoing everything and just have the front brakes left. i can build up pressure with several pumps of the brake but if i lay off for a second while it dosent lose ALL pressure theres a noticable loss and while test riding the brakes are weak and inneficient.

Ive rebuilt the master cylinder
dissassembled and cleaned out both calipers twice
checked all the lines and connections for leaks and havent found any
bled the system going on seven times in the correct sequence including alternating bleeding the master cylinder itself.
what am I missing!?!?!?!?!?!?!?!
Click to expand...

Does that bike have the anti dives units on it ? I don'[t recall.
 
are you using the original 30 year old lines ? or did you get new ones, are you bleeding them in the right sequence ? I found when I bled and finished with mine they still felt soft, so I pumped the lever 5-10 times, held and opened the bleeder valve, once that was all done the last thing I did was pump the lever and held it and strapped it pulled back towards the handlebar over night.

In the morning I released it and it was working properly no need to pump to builld up pressure, and no loss of pressure and brakes felt good.

.
 
mrbill5491 said:
Okay, someone in the forum should be able to help you since you still have the anti dives on. I have not a clue if there is a specific way to bleed those.
Click to expand...

they are bled the same sequence as normal brakes. furthest from M/C first.
so it would be left A/D,left caliper,right A/D,right caliper
 
still using old lines, following manual bleeding sequence, 1. L anti dive, 2. L caliper, 3. R a/d 4. R caliper. just tried putting a known good master cylinder from a different bike and got the same results. pump the brake a couple times and its good and stiff, let go count to 5 and i can pull the lever in almost all the way to the handle bar.
 
you sure all the air is out....

try as I mentioned, pump the lever, tie it back overnight, and see how it is in the morning

.
 
GateKeeper said:
you sure all the air is out....

try as I mentioned, pump the lever, tie it back overnight, and see how it is in the morning

.
Click to expand...

im as sure as i can be with it still not working? if that makes sense. ive bled them twice more at this point with the swapping of the new master cylinder. pump, hold lever, crack bleed, tighten, repeat until theres no more air bubbles in the stream, move to the next...ill try tieing it back tonight when i finally give up.
 
it was the only way I was able to stop it from being spongy, pump the lever until it get hard/stiff and hold, tie it back and leave it overnight.

it's worth a shot
 
it has to be M/C seals. we had the same problem on here a while back and replacement seal kit cured it.
i had the same problem on my bike as well on the rear. new seals in caliper,new brake line,swapped M/C's same symptoms as yours. replaced my M/C with OEM seal kit and hey presto, bled up and rock solid brake.
 
Agemax said:
it has to be M/C seals. we had the same problem on here a while back and replacement seal kit cured it.
Click to expand...

thats what I kept thinking in the begainning so i rebuilt it with the k&l m/c rebuild kit after I cleaned out the calipers so it already has new seals. got the brake lever tied back now...
 
Soon as i read "K&L" I thought the same thing. Also I go back and forth a few times on each front caliper and rebleed them even after I have ised the mighty vac. I use a clear tubing and hand bleed them each again to be 1000% certain there isnt any residual air anywhere.
 
Since you STILL have the old brake lines on, this would be a good time to upgrade to the SS lines.
 
tied it back overnight, still a little spongy. If I had to ball park it id say im in the realm of 85-90% of my braking capability. enough to feel ok on the street stopping at lights and signs but enough to worry about that 10-15% in a real oh ****! situation
 
Someone a few months ago had a similar problem. I thin k it was Steve that sorted it(?) Anyway, the fix was to use a green dish scrubbie and go around the piston seals in the calipers to relieve them just ever so slightly so the pistons would move freer.

Anyone remember that thread and the original posters name???
 
Don't use the lever to bleed the brakes. Take off the lever and use a screwdriver or whatever to push in the piston. Tiny air bubbles love to hide behind the piston in the M/C since the lever does not push the piston in the whole way.
 
ok, I had to take a step back and breathe for a while but STILL no dice. heres where Im at.

1. NEW master cylinder.
2. all NEW hoses.
3. NEW seals in caliper
4. all NEW crush washers
5. calipers and pistons dissasemled and cleaned out
6. brake lever tied back and left overnight several times
7. bled with a mighty vac

I looked at the suggestion on the last post and I dont think thats it as the pistons seat back in to the caliper after removal with the usual amount of resistance.

The only x factor Im seeing is when bleeding, the anti dive bleeders shoot what I would consider a normal amount of fluid when cracked open to bleed, while the calipers themselves sometimes will only dribble.

PLEASE!!!!! Im starting to lose my mind on this!!!!! WHAT AM I MISSING!?!?!?!?!?!?!?
 
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