Replacing them is a serious job – not difficult with the right tools – but doing the job properly is critically important. We will try with easy steps to guide you through the process but don't attempt it in you're not sure.
Before you start, check that you've got the correct hose kit and give everything a good wash. Use a soft brush around the brake hose banjo bolts, bleed nipples, and master cylinder reservoir so they're clean and free from any dirt. Dry thoroughly . You may need to remove at least the top part of the fairing cowl to gain access to work, check that.
- Wrap a rag around the master cylinder reservoir and remove the cap and bellows. Use a sucker or large syringe to empty the fluid. Failing that paper towel works but you'll need a good supply, dripping brake fluid ruins paint and body work in seconds, so clean any spillages immediately with warm soapy water. Clean the inside of the reservoir, the cap, and bellows with a clean piece of rag. Refit the reservoir cap.
- Disconnect any hose-holding clips or brackets. Using a container below the bottom of the hoses to collect draining fluid, undo the bottom hose banjo bolts – at the caliper – fully and loosen the top – master cylinder – banjo bolt.
- With a rag under the hose end, remove the top hose banjo bolt fully. The hoses should now be free to remove. Leave them with the ends in you receptacle to drain fully. Check again for spillages and that no small pieces of grit are sitting where the hose ends.
- You're now ready to fit your new hoses so identify which new hoses go where. Loosely fit them finger tight, with all the banjo washers in their correct places.
- Nip up the banjo bolts with a spanner, not fully tight, and check the hoses are correctly routed and not fouling the fork legs, throttle cables, fork yoke or mudguard. Refit hose clips or brackets. Tighten the banjo bolts to the specified torque wrench. Bounce the forks to check the hoses are clear of fouling and, by topping them out, that the hoses aren't pulled tight when the fork are fully extended.
- You're now ready for bleeding. With that wad of rag still in place, remove the master cylinder reservoir cap and fill the upper level. Remove the rubber cover from the bleed nipple on the master cylinder, use a ring spanner to crack off the nipple, nip it back up, then, with the spanner still in place, fit a length of clear pipe onto the nipple. Place the remaining end of the pipe into the bottom of the jar you used earlier, making sure that the bottom of the pipe is submerged in brake fluid. Loosen the nipple and, with the adjuster set for maximum span, gently pump the brake lever. Air bubbles should escape from the bleed pipe into the jar. Don't let reservoir level get too low. Before topping up, hold the brake lever in and nip up the bleed nipple. Keep pumping the brake lever even after any air bubbles have gone as fluid will still be finding its way down the hoses. When you can feel pressure in the system, nip the bleed nipple up.
- Starting with the caliper furthest away from the master cylinder, with the ring spanner on the bleed nipple and the bleed hose submerged in the jar again, bleed as you did the master cylinder, keep an eye on the reservoir level – don't let it run 'dry' – or you'll be starting again. Tighten the bleed nipple to the recommended torque and repeat the process on the second caliper (if there is one).
- Check the lever doesn't feel 'spongy'. If it does, repeat the process and for the last couple of pumps, nip up the bleed nipple, release the brake lever, then squeeze while slowly undoing the nipple until the pressure starts to release and the brake lever slowly comes back to the handlebar. Nip the nipple up just before the brake lever reaches the bar. Top the reservoir up to the “full” mark, and refit the rubber bellows and cap.
- Give everything a nut and bolt check and a bloody good wash with hot soapy water. Dry off and “twizzle” tissue paper down the bleed nipple orifices to draw any fluid out. Dry everything and give the lever a hard squeeze and check for leaks. To be doubly sure, pull the lever to the bars with a cable tie and leave for a few minutes. If there are no leaks, remove all tissue and rags refit the rubber covers on the nipples. After your first ride check for leaks again.