Nov 1: Still struggling to get pressure in my front lines

  • chopper1963
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Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 07:33
#918566
1983 KZ750L3.
Rebuilt calipers with Kawi parts.
Set of steel lines
Set of stock rubber lines

We have tried everything seemingly to get brake pressure in these brakes but no dice. Used a mity-vac. Back-filled the calipers. Still nothing. Growing very frustrated. Sprayed all connections with soapy water and no bubbles. What can we be missing? The master has been tested and squirts fluid ...

All suggestions welcome.

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  • asphalt900
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Re: Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 08:05
#918567
If old lines, are you sure they are free-flowing? Have had/seen plenty that were plugged-up with old debris. If you have a switch on your splitter air can get trapped in there too.
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  • Wookie58
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Re: Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 08:18 - 01 Nov 2025 08:20
#918568
If you let it stand with the nipples open does the fluid level drop in the master as the fluid moves through (gravity bleed) be patient will take a few hours
PS: when you re-fitted the callipers did you give them a squirt of air in the bleed hole to push the pistons out (sometimes helps, if the pistons are pushed fully back they can restrict flow)
1982 KZ1000 Ltd
www.kzrider.com/forum/11-projects/617631...-82-begins?start=192
kzrider.com/filebase-alias?view=download...d-fault-diagnosis&ca
Last edit: 01 Nov 2025 08:20 by Wookie58.

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Re: Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 08:35 - 01 Nov 2025 08:39
#918569
As asphalt900 said air gets trapped in the splitter.
Unbolt it from the yoke and position it hanging with the master cylinder banjo as the highest point. This will allow the splitter to fill without trapping air. 
Once bled loosen the mc cap and cable tie the lever back against the grip and leave it overnight. This will allow micro bubbles to rise back to the mc reservoir. 

Last edit: 01 Nov 2025 08:39 by Warren3200gt.
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Re: Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 08:43
#918570
We blew the lines out with 125 PSI shop air compressor.

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  • Wookie58
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Re: Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 08:54
#918571
The master may squirt fluid but does it "build pressure" - as long as there is a piston and seal in there it will squirt !!
1982 KZ1000 Ltd
www.kzrider.com/forum/11-projects/617631...-82-begins?start=192
kzrider.com/filebase-alias?view=download...d-fault-diagnosis&ca
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Re: Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 08:56
#918572
How would we test to make sure that it builds pressure and not just squirts fluid?  All three masters we tried are new.

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Re: Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 09:02
#918573
chopper1963 wrote:
How would we test to make sure that it builds pressure and not just squirts fluid?  All three masters we tried are new.
That pretty much eliminates the master - if you are using rubber lines you can "clamp the line from the master to the slitter then "carefully pull the lever and see if it goes hard "don't force it" this will confirm the master is building pressure - if you are using stainless lines DON'T CLAMP THEM
1982 KZ1000 Ltd
www.kzrider.com/forum/11-projects/617631...-82-begins?start=192
kzrider.com/filebase-alias?view=download...d-fault-diagnosis&ca
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Re: Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 10:00
#918574
Thanks. We will keep trying.

On the upside the bike now runs fantastic. Wonderfully great. I've taken it around the block with zero brakes which is interesting to say the least.

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Re: Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 12:12
#918578
Wookie58 wrote:
chopper1963 wrote:
How would we test to make sure that it builds pressure and not just squirts fluid?  All three masters we tried are new.
That pretty much eliminates the master - if you are using rubber lines you can "clamp the line from the master to the slitter then "carefully pull the lever and see if it goes hard "don't force it" this will confirm the master is building pressure - if you are using stainless lines DON'T CLAMP THEM
EDIT: if you are using stainless lines you can still test the master - where the hose joins the splitter replace the banjo bolt with a normal bolt without a hole (I believe it's M10x1.25) and again apply the lever carefully
 
1982 KZ1000 Ltd
www.kzrider.com/forum/11-projects/617631...-82-begins?start=192
kzrider.com/filebase-alias?view=download...d-fault-diagnosis&ca
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Re: Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 14:21 - 01 Nov 2025 14:46
#918581
I had the same problem with my front m/c, no matter what I tried. What finally worked was emptying the whole deal then using a " turkey baster " pump I backfilled the entire system from the bleed connection on the caliper.  Go SLOWLY and wrap a rag around the master in case of overflow.

 
Scotty

1974 Z1A
Yoshimura 987
welded Z1 crank
Andrews 1X Cams
Delkevic 4 into 1
Superbike bars
530 conversion
Last edit: 01 Nov 2025 14:46 by sf4t7. Reason: fo-to
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Re: Nov 1: Still struggling to get pressure in my front lines

01 Nov 2025 19:31
#918585
We finally got *some* brakes in it late today. Going to do the lever pulled all night trick. Probably sacrifice a chicken or pig at dawn, hope for the best.
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