Bleeding
Okay, Let’s Go
Remove the existing brake lines from the bike carefully. Start by removing all the old washers, and then drain the system of brake fluid – ideally without getting any on your paintwork – and ensure all sealing surfaces are clean and in good condition. Fit the HEL brake line kit using the copper washers supplied, and check the pitch of your new HEL banjo bolts (supplied) with those you’re replacing. Note, this is especially important with Suzuki motorcycles, as some models use both M10x1.00mm and M10x1.25mm-pitch banjo bolts.
Prepping
While experienced mechanics and enthusiasts might be happy bleeding bike brake systems solo, it’s easier if two people do it.
Of course, you’ll need clean, fresh brake fluid that has settled – preferably overnight so there are no air bubbles in it – plus a length of plastic tubing that fits tightly to the bleed nipple, and a glass container so you can see the air and old fluid being expelled from the system.
Also, cover areas around the master cylinder and the bleed nipples to protect from accidental spillage, and ensure surrounding areas are clean to avoid dirt entering the system. Attach plastic tubing to one of the bleed nipples and open slightly so you can get most of the old fluid out before removing the existing hoses. It’s not uncommon for bleed nipples to be seized in the calipers, thanks to corrosion and salt from winter roads, so you might take this opportunity to also replace the mild steel nipples with stainless steel ones.
With the bleed nipples undone, make sure the brake reservoir has plenty of fluid in it, and then rest the cap back on top to stop fluid squirting out when you begin bleeding.
Priming
If you have a twin disc system, bleed one caliper at a time, tackling the one furthest from the master cylinder first.
Attach the tube to the bleed nipple and place the other end in a clean glass jar. Pour some clean brake fluid into the jar, so the end of the tube is submerged – this way you won’t pull air back in to the system. Then open the bleed nipple, and squeeze and release the brake lever slowly to give the master cylinder enough time to suck in fresh fluid from the reservoir. Keep an eye on the master cylinder reservoir and make sure the fluid level does not fall below the minimum mark, or you might start sucking air into the system.
As you prime, fluid may be pulled back into the system from the jar. Just make sure the tube is always immersed in fluid so you don’t draw air into the system from this end, either. It shouldn’t take too much levering to fill the system – when it’s full, tighten the bleed nipple.
Bleeding
Open the bleed nipple slowly, for roughly half a turn, while simultaneously squeezing the brake lever in (or pressing the foot-pedal). As you hold the lever or pedal in, you should see air bubbles or fluid entering the glass jar. Old brake fluid can be anywhere from off-white to brown, or even black if the change is long overdue! Fluid or air release will only take a few seconds. Then close the nipple before releasing the brake lever/pedal. Now check the fluid level in the reservoir, and top up if necessary.
Repeat this operation until no more bubbles appear and the fluid coming out is clear, ensuring the master cylinder remains topped up. If you have a twin system, simply repeat the process with the other caliper.
You should now have a brake system with a good solid feel to it. The lever should ‘travel’ slightly and then meet firm resistance, but if – when you continue to apply pressure – you experience a slow drop in resistance or sponginess, it’s likely there is still air in the system. Try bleeding again and check all parts are tightened to the correct torque setting. Also, check lines aren’t trapped on full lock, and that there aren’t any fluid leaks anywhere in the line or system.
Final Checks
Give the system a meticulous visual inspection before test riding. By test- riding, we mean going slowly forward a few feet, applying the brakes, and then checking again for any fluid leaks. Then ensure everything is tightened correctly and the brakes still have a good solid feel to them.
Seriously – don’t ride your bike until you’re certain you’ve bled the brakes correctly. Check all end fittings are attached securely to each line. Check line(s) for clearance, and that the kit has been installed without any kinks or twists. Make sure full suspension travel and steering lock are unaffected, and that the hoses aren’t stretched or trapped in any way. Then tighten the banjo bolt to correct torque.
If in ANY doubt, get your local dealer to bleed the system for you.
Banjo Bolt Torque Settings
- Minimum – 20Nm (14 lbf⋅ft)
- Maximum – 33Nm (24 lbf⋅ft)
Troubleshooting
Not all calipers have bleed nipples at their highest point. This can cause a small pocket of air to become trapped above the nipple, which can be difficult to remove and cause spongy brakes. You can get around this by taking the caliper off and making sure the nipple is at the highest point during bleeding. Just remember to put a spacer between the pads to stop the pistons popping out – and to make it easier to refit the caliper.
A similar problem occurs with some racing bikes with steeply angled handlebars, when a small pocket of air can become trapped where the brake hose arches over the master cylinder. This can be remedied easily by re- routing the hose, or by injecting brake fluid very carefully through the bleed nipple in the caliper, using a syringe. Bear in mind that the fluid in the reservoir may overflow as a result. Alternatively, you can fit a banjo bolt with a bleed nipple to the master cylinder, and bleed this before the rest of the system.
If you can’t get rid of sponginess, no matter how carefully you bleed the system, you may have a sealing problem. This can this happen when the tiny hole the fluid passes through on its way from the reservoir to the master cylinder gets blocked. Even the smallest speck of dirt can cause this – which is why cleanliness is so important when bleeding brakes.
If you’re not fully confident bleeding your own brakes, ask your local dealer to do it for you. Don’t be tempted to use 'self bleed' gadgets unless you absolutely have to – while they keep the nipple open with a non-return valve to stop air re-entering the system, the bleed nipple has a threaded end which screws into the caliper, and air can easily be sucked into the caliper here if the nipple is loose in the threaded part. It may only be a small amount, but it kind of defeats the object of removing air!
When you’ve bled your brakes successfully, make sure both bleed nipples and the banjo bolts are tightened to the torque settings given here, and top up the master cylinder reservoir with fresh brake fluid to the required level. Most standard reservoirs show an upper and lower limit. Be careful not to overfill, as this can cause hydraulic locking of the system, and binding of the brakes. Nobody wants that…
