CP3125 Family

CP3125 Family

 The original adjustable ratio master cylinder used by GP and Superbike teams in the 80’s. Can be used to upgrade any brake system. Available for single or twin brake applications and is supplied with integral reservoir only.

Features:
- The original adjustable ratio brake master cylinder can be used to upgrade any brake system.
- Incremantal ratio adjustments, Ratio is 6.4 - 9.34:1.
- Supplied with integral fluid reservoir.

Typical Applications:

- Historic GP & Superbike Machines & Road.

Assembly Part Numbers:
- CP3125-2 (16mm to 19mm effective bore).

Ratio Adjustments Guide.
This variable ratio master cylinders has a screw to adjust the ratio. This adjuster is moved to and away from the handlebar with the effects detailed in the table below.

GUIDE TO ADJUSTMENT

SCREW ADJUSTER

BRAKING

LEVER TRAVEL

LEVER FEEL

IN - CLOCKWISE

DECREASED

DECREASED

HARDER

OUT - ANTI CLOCKWISE

INCREASED

INCREASED

SOFTER


Technical Specifications & Notes.

- Master cylinder will be supplied with the screw adjuster set at position 0 (i.e. with the adjuster flush with locknut as drawn) at this setting piston travel is at its maximum, which will give best conditions for bleeding the brake system. Typical working stroke is shown as a guide (see table opposite) only working stroke should be set to riders preference. After initial setting only small adjustments, typically ±½ turn should be necessary to suit differing conditions.
- Lever travel will usually increase slightly in dynamic applications over static settings due to disc runout etc. it is therefore advisable to set lever feel on the hard side for initial test.
- Important: If any impact is sustained on lever causing a high pressure input to brake system, the whole system should be either replaced or sent back to AP Racing for examination.

  • Effective Bore Size 16mm to 19mm
    Actual Bore Size - CP3125-2 - 19mm (0.74")
    Hydraulic Threads M10x1.0
    Weight Kg 0.475
    Bleed Screw Tightening Torque 5.5Nm (4lbs/ft)
    Repair Kit CP3125-2 = CP3125-2RK
  • Click on the link to download the relevant drawing.

  • Additional Information

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