Hey guys unsure if there is a thread about this already but hasn't come up in searches.. The ZXR has been sitting a while and the front brakes are gone.. Super spongy almost no stopping power on its first ride in a good 6 or 7 months. I know the brake pads have approx 600kms on them so quite new ish. Just after a guide or maybe instructions on servicing the front brakes? Bleeding the brake? Cheers
Brake fluid is hygroscopic (it absorbs moisture). Brake fluid is supposed to be incompressible (as a hydraulic fluid) but the ingress of water leads to sponginess and poor brake performance due to the water in the fluid boiling (aka brake failure)
Unless it has been done recently, I would suggest completely stripping and cleaning the calipers, new seals (with plenty of rubber grease), replace the hoses if they are original and new fluid. The master 'should' be ok, but if in doubt then strip and clean it too.
Yep I am keen to do that. Haven't done this before are there any guides on here? And where do I get the seals etc
Here is a complete kit including new pistons. https://www.ebay.com.au/itm/Kawasak...rebuild-kit-ZX2R-1991-1992-1993-/153162419099 Just seals. https://www.ebay.com.au/itm/Kawasak...caliper-seal-kit-1993-1994-1995-/161283902085 or https://www.webkyosale.com/index.php?main_page=product_info&products_id=557402 Or maybe find the part numbers of the bits you need and visit a Kawasaki dealer as I'm sure the seals would have been used on other bikes.
I'm sure that doing a total rebuild is the optimum plan but its not really a super simple, potential incident free operation, especially the first time its done. I'd bleed the system first and go for a very careful, gentle ride to free up the pistons and possibly discover the brakes are working perfectly and don't require a full rebuild. If you still need to do the rebuild these are some of the points i'd consider. If you are planning on using the hydraulic pressure to remove the pistons you need to get the air/water out of the system first anyway. so, as mentioned above, bleed the system. If using compressed air then wrap the calliper in a large, soft rag, piston aimed at the floor. You can potentially do serious injury to yourself or damage items in the shed if the piston erupts free from its housing and goes flying across the workshop. Also be careful to use the right screw driver to remove the master cylinder phillips head screws, if insanely tight/corroded, use an impact driver gently. These are still made of swiss cheese on many bikes and rounding one off can add vast amounts of unnecessary time to the rebuild. After the rebuild getting pressure up to the system can also be a total pain.. If the system just refuses to bleed, gently tap the caliper, any brake line junction then the master cylinder itself with a rubber mallet while pumping the lever, this often dislodges air bubbles. If it still refuses to bleed, get a large rubber band,( a section of motorcycle inner tune is perfect), put it around the brake lever and handle bar so the lever is pulled in as far as it will go and leave the bike overnight,, visiting it occasionally to pump the lever and give the above mentioned sections another tap with the rubber mallet..
