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Front brake master cylinder may be faulty

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glennz1b
Regular Poster
Posts: 43
Joined: 15th Aug 2007
Location: derbyshire

Front brake master cylinder may be faulty

#1 PostAuthor: glennz1b » Fri Mar 14, 2025 5:21 pm

Hi all
I have spend all afternoon trying to get the front brakes to work correctly on my Z, The system has bled well and the calipers release and grip the disc when the lever is operated, My problem is
The master cylinder is brand new from Z power and i am now thinking the 2 holes in the pressure cylinder are drilled to far down towards the exit port as there is a lot of lever movement before the small hole is covered and pressure built up, leaving a small operating area to press the pistons before the plunger bottoms out in the cylinder, when the lever is pulled in you can see all the fluid coming up from the small hole and does not stop until the lever has moved a good way. I have the calipers / brakes basically working as they should but it is very close to full travel of the hydraulic piston which to me is not right, I have never had a problem like this in the passed. So what do you think, Is it a faulty master cylinder ? Has anybody had a similar problem with a Z power aftermarket master cylinder
Cheers Glenn

Paul Spencer
new poster
Posts: 9
Joined: 4th Apr 2020
Location: Maidenhead

Re: Front brake master cylinder may be faulty

#2 PostAuthor: Paul Spencer » Sat Mar 15, 2025 4:23 am

Hi Glenn,
The only time I experienced a problem identical to what you describe was when I tried using a single disk master cylinder which has a 9/16" piston with a twin caliper set up. Twin disks need a 5/8" master cylinder. Is this what you bought?

glennz1b
Regular Poster
Posts: 43
Joined: 15th Aug 2007
Location: derbyshire

Re: Front brake master cylinder may be faulty

#3 PostAuthor: glennz1b » Sat Mar 15, 2025 9:25 am

Hi Yes i ordered a twin disc master cylinder which it says on the box is 15,8mm (5/8) but i cant see any size on the unit itself. i may have to strip it down to measure the bore.

DeadZedDave
100Club
100Club
Posts: 246
Joined: 1st Nov 2021
Location: Newcastle

Re: Front brake master cylinder may be faulty

#4 PostAuthor: DeadZedDave » Sat Mar 15, 2025 12:21 pm

Do you still have standard type callipers fitted - I remember you were posting last November about fitting some upgrade 2 or 4 pots ?

glennz1b
Regular Poster
Posts: 43
Joined: 15th Aug 2007
Location: derbyshire

Re: Front brake master cylinder may be faulty

#5 PostAuthor: glennz1b » Tue Mar 25, 2025 6:59 am

Hi yes i have fitted Suzuki 600 bandit calipers which have 2 pistons in each caliper. I have returned the master cylinder back to Z power and they have sent me another replacement which is a lot better.


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