PROX Front Brake Master Cylinder Rebuild Kit for HONDA, KAWASAKI, YAMAHA and SUZUKI 1985-2027

The PROX avant 37.910004 brake master cylinder rebuild kit is designed for SUZUKI DR 125, DR 250, DRZ 400, RM 125, RM 250, HONDA CRF 125, CRF 150, CRF 230, CRF 250, KAWASAKI KFX 400, KFX 450, KLR 650, KLX 650 and YAMAHA GRIZZLY 700, XT 600, YFZ 450 from 1985 to 2027. This kit rebuilds the brake master cylinder (piston, cups, spring and seals, depending on the part number). Worn cups let the lever or pedal sink and cost you braking power.

Specifications

• Brand: PROX
• Manufacturer part number: 37.910004
• Weight: 30 g

When to replace it?

• Lever or pedal that slowly sinks when you hold the pressure on.
• Fluid leaking at the master cylinder.
• Spongy brakes despite a proper bleed.

Rebuild the master cylinder as soon as the lever or pedal travel gets longer for no obvious reason, or if it leaks.

Fitting tips

1. Drain the system and remove the master cylinder.
2. Remove the circlip, take out the old piston and clean the bore: it must be smooth, with no scoring.
3. Fit the new piston with its cups lubricated with fresh brake fluid, the same way round as the old one.
4. Reassemble, fill and bleed the system, then check the brakes with the bike stationary.

Why PROX?

ProX Racing Parts has been supplying engine and clutch parts to motocross riders since 1975, from its headquarters near Amsterdam. According to its catalogue, most of its parts are made in Japan, by manufacturers that also produce parts for the Japanese motorcycle makers.

Spare parts and items to plan

• Brake fluid : MOTUL 500 ml · MOTUL 5 L
• Brake pads : AP RACING LMP294ORR · AP RACING LMP294OR

Frequently asked questions

Front or rear?
The kits are specific: check the position given in the product name and in the compatibility list.

Compatibility

Check the exact model and year of your bike in the list below before ordering.

Fits:
HONDA CRF 125 2027
HONDA CRF 125 2026
HONDA CRF 125 2025
HONDA CRF 125 2024
HONDA CRF 125 2023
HONDA CRF 125 2022
HONDA CRF 125 2021
HONDA CRF 125 2020
HONDA CRF 125 2019
HONDA CRF 125 2018
HONDA CRF 125 2017
HONDA CRF 125 2016
HONDA CRF 125 2015
HONDA CRF 125 2014
HONDA CRF 150 2017
HONDA CRF 150 2016
HONDA CRF 150 2015
HONDA CRF 150 2014
HONDA CRF 150 2013
HONDA CRF 150 2012
HONDA CRF 150 2011
HONDA CRF 150 2010
HONDA CRF 150 2009
HONDA CRF 150 2008
HONDA CRF 150 2007
HONDA CRF 150 2006
HONDA CRF 150 2005
HONDA CRF 150 2004
HONDA CRF 150 2003
HONDA CRF 230 2019
HONDA CRF 230 2018
HONDA CRF 230 2017
HONDA CRF 230 2016
HONDA CRF 230 2015
HONDA CRF 230 2014
HONDA CRF 230 2013
HONDA CRF 230 2012
HONDA CRF 230 2011
HONDA CRF 230 2010
HONDA CRF 230 2009
HONDA CRF 230 2008
HONDA CRF 230 2007
HONDA CRF 230 2006
HONDA CRF 230 2005
HONDA CRF 230 2004
HONDA CRF 230 2003
HONDA CRF 250 2025
HONDA CRF 250 2024
HONDA CRF 250 2023
HONDA CRF 250 2022
HONDA CRF 250 2021
HONDA CRF 250 2020
HONDA CRF 250 2019
KAWASAKI KFX 400 2006
KAWASAKI KFX 400 2005
KAWASAKI KFX 400 2004
KAWASAKI KFX 400 2003
KAWASAKI KFX 450 2014
KAWASAKI KFX 450 2013
KAWASAKI KFX 450 2012
KAWASAKI KFX 450 2011
KAWASAKI KFX 450 2010
KAWASAKI KFX 450 2009
KAWASAKI KFX 450 2008
KAWASAKI KLR 650 2017
KAWASAKI KLR 650 2016
KAWASAKI KLR 650 2015
KAWASAKI KLR 650 2014
KAWASAKI KLR 650 2013
KAWASAKI KLR 650 2012
KAWASAKI KLR 650 2011
KAWASAKI KLR 650 2010
KAWASAKI KLR 650 2009
KAWASAKI KLR 650 2008
KAWASAKI KLR 650 2007
KAWASAKI KLR 650 2006
KAWASAKI KLR 650 2005
KAWASAKI KLR 650 2004
KAWASAKI KLR 650 2003
KAWASAKI KLR 650 2002
KAWASAKI KLR 650 2001
KAWASAKI KLR 650 2000
KAWASAKI KLR 650 1999
KAWASAKI KLR 650 1998
KAWASAKI KLR 650 1997
KAWASAKI KLR 650 1996
KAWASAKI KLR 650 1995
KAWASAKI KLR 650 1994
KAWASAKI KLR 650 1993
KAWASAKI KLR 650 1992
KAWASAKI KLR 650 1991
KAWASAKI KLR 650 1990
KAWASAKI KLR 650 1989
KAWASAKI KLR 650 1988
KAWASAKI KLR 650 1987
KAWASAKI KLX 650 1996
KAWASAKI KLX 650 1995
KAWASAKI KLX 650 1994
KAWASAKI KLX 650 1993
SUZUKI DR 125 1988
SUZUKI DR 125 1987
SUZUKI DR 125 1986
SUZUKI DR 250 1995
SUZUKI DR 250 1994
SUZUKI DR 250 1993
SUZUKI DR 250 1992
SUZUKI DR 250 1991
SUZUKI DR 250 1990
SUZUKI DRZ 400 2016
SUZUKI DRZ 400 2015
SUZUKI DRZ 400 2014
SUZUKI DRZ 400 2013
SUZUKI DRZ 400 2012
SUZUKI DRZ 400 2011
SUZUKI DRZ 400 2010
SUZUKI DRZ 400 2009
SUZUKI DRZ 400 2008
SUZUKI DRZ 400 2007
SUZUKI DRZ 400 2006
SUZUKI DRZ 400 2005
SUZUKI DRZ 400 2004
SUZUKI DRZ 400 2003
SUZUKI DRZ 400 2002
SUZUKI DRZ 400 2001
SUZUKI DRZ 400 2000
SUZUKI RM 125 1986
SUZUKI RM 125 1985
SUZUKI RM 250 1985
YAMAHA GRIZZLY 700 2018
YAMAHA GRIZZLY 700 2017
YAMAHA GRIZZLY 700 2016
YAMAHA GRIZZLY 700 2015
YAMAHA GRIZZLY 700 2014
YAMAHA GRIZZLY 700 2013
YAMAHA GRIZZLY 700 2012
YAMAHA GRIZZLY 700 2011
YAMAHA GRIZZLY 700 2010
YAMAHA GRIZZLY 700 2009
YAMAHA GRIZZLY 700 2008
YAMAHA GRIZZLY 700 2007
YAMAHA XT 600 1995
YAMAHA XT 600 1994
YAMAHA XT 600 1993
YAMAHA XT 600 1992
YAMAHA XT 600 1991
YAMAHA XT 600 1990
YAMAHA YFZ 450 2025
YAMAHA YFZ 450 2024
YAMAHA YFZ 450 2023
YAMAHA YFZ 450 2022
YAMAHA YFZ 450 2021
YAMAHA YFZ 450 2020
YAMAHA YFZ 450 2019
YAMAHA YFZ 450 2018
YAMAHA YFZ 450 2017
YAMAHA YFZ 450 2016
YAMAHA YFZ 450 2015
YAMAHA YFZ 450 2014
YAMAHA YFZ 450 2013
YAMAHA YFZ 450 2012
YAMAHA YFZ 450 2011
YAMAHA YFZ 450 2010
YAMAHA YFZ 450 2009
YAMAHA YFZ 450 2008
YAMAHA YFZ 450 2007