Bleeding the Brakes on a 2018 Ducati Scrambler Desert Sled
Shop parts for a 2018 Ducati Scrambler Desert Sled Motorcycle.
Start With the Desert Sled’s Brake Layout
The 2018 Ducati Scrambler Desert Sled stops on hydraulic disc brakes at both ends, and ABS is part of the package. That gives you two completely separate hydraulic circuits to look after: a front system fed by the master cylinder on the handlebar, and a rear system fed by the master cylinder down at the pedal. Each one has its own reservoir, its own line, and its own bleeder at the caliper, so each one gets bled on its own. Nothing about the front bleed affects the rear, and vice versa.
The ABS modulator sits between the master cylinders and the calipers. For a normal fluid refresh — pushing fresh fluid through until the old stuff is gone — you work through the caliper bleeders exactly as you would on a bike without ABS. The modulator only becomes a problem if air has actually gotten inside it, which is a different job entirely and one best left to a dealer with the right diagnostic equipment.
How to Tell a Bleed Is Due
The classic symptom is a lever that feels soft or spongy, or one that now travels noticeably closer to the grip than it used to. On the rear, a pedal that feels long or vague tells the same story. A lever that holds firm at first but slowly creeps toward the bar while you hold steady pressure is another warning sign.
Fluid condition matters just as much as feel. Pop the reservoir cap and look: fresh fluid is clear and pale, while fluid that has been in service for a couple of seasons turns dark, cloudy, or tea-colored. Brake fluid is hygroscopic, meaning it pulls moisture out of the air over time. That moisture lowers the fluid’s boiling point, and under hard, repeated braking — exactly the kind of use a Desert Sled sees on a twisty road or a gravel descent — fluid that boils creates vapor, the lever goes long, and you get brake fade. Many riders simply refresh the fluid on a regular interval rather than waiting for a symptom.
You also need a bleed any time the system has been opened to air: new brake lines, a caliper rebuild, master cylinder work, or a reservoir that ran dry.
Tools and Supplies to Have on the Bench
- Fresh brake fluid in the type printed on your master cylinder reservoir cap, from a sealed container. Do not substitute a different type.
- A box-end wrench that fits the bleeder valve snugly — a snug fit matters more than any particular size.
- A length of clear tubing that pushes firmly over the bleeder nipple without leaking at the joint.
- A small catch bottle to hang the tubing into.
- Rags or shop towels, plus a syringe or turkey baster for pulling old fluid out of the reservoir.
- The correct driver for the reservoir cap screws.
- Optional but genuinely helpful for solo work: a one-way check-valve bleeder or a vacuum bleeder.
Setting Up Safely
Get the bike upright and stable on a stand before you touch anything. For the front circuit, turn the handlebar so the reservoir on the master cylinder sits level — a tilted reservoir will spill the moment the cap comes off. Then drape rags over the tank area, the plastics, the instrument cluster, and anything painted below the reservoir and caliper. Brake fluid attacks paint and many plastics on contact, and a single stray drip can leave a permanent mark. If a spill does happen, wipe it up immediately and rinse the area with water rather than waiting until the job is done.
Bleeding the Front Brake
- Remove the reservoir cap and diaphragm, then use the syringe or baster to draw most of the old fluid out. Leave a little at the bottom so you do not push air into the line.
- Top the reservoir up with fresh fluid from the sealed container.
- Push the clear tubing onto the front caliper bleeder and route the other end into the catch bottle, with the bottle positioned so the tubing runs upward before it drops. That keeps air from traveling back toward the caliper.
- Fit the box-end wrench onto the bleeder.
- Squeeze the front lever and hold it firmly against the grip.
- Open the bleeder about a quarter turn. Fluid and any trapped air will push out through the tubing. Watch the reservoir level as you do this.
- Close the bleeder fully before you release the lever. Releasing with the bleeder open draws air straight back into the caliper.
- Release the lever slowly, then top the reservoir back up.
- Repeat the squeeze–open–close–release cycle until the fluid coming through the tubing is clean, bright, and completely free of bubbles. Keep the reservoir topped off at every cycle so it never runs low enough to swallow air.
If your bike carries more than one front caliper, bleed them one at a time rather than trying to do both at once. As a general habit, start with the caliper farthest from the master cylinder and work toward the closest one.
Bleeding the Rear Brake
The rear circuit follows the same logic with a different input. Level the rear reservoir, protect the surrounding bodywork, and pull the old fluid out before refilling. Attach the tubing and catch bottle to the rear caliper bleeder, then press and hold the brake pedal instead of the lever. Crack the bleeder a quarter turn, let the fluid and air escape, close it snugly, and only then release the pedal. Repeat until the fluid runs clean and bubble-free, topping the reservoir as you go.
Finishing Up and Checking for Leaks
Once both circuits run clean, close each bleeder snugly — firm enough to seal, but not so hard that you damage the seat or the caliper threads. Fill each reservoir to the level marking molded into it, reinstall the diaphragm and cap, and wipe down every surface you touched. Then inspect the bleeder fittings and the banjo bolts at the master cylinder and caliper for any weeping. A dry paper towel pressed against each joint will show a leak immediately.
Testing Before You Ride
Both the lever and the pedal should feel firm and consistent, and neither should sink slowly while you hold steady pressure. Spin each wheel by hand to confirm the brakes are not dragging. Then, in a safe open area at low speed, apply the front and rear brakes separately and together before riding normally. If anything feels soft, stop and investigate rather than riding it out.
When to Hand It Off to a Shop
If the lever will not firm up after several full bleeding cycles, if it only firms up when you pump it, or if bubbles keep appearing no matter how long you work, something else is going on — a worn master cylinder seal, a pinhole in a line, or air trapped somewhere a caliper bleed cannot reach. Fluid weeping from the master cylinder or caliper is another stop sign. Most importantly, if the reservoir ever ran dry, or if the ABS unit or its lines were disconnected, air may now be inside the modulator. That requires dealer-level equipment to cycle and bleed properly, and no amount of pumping at the caliper will fix it. In any of those cases, put the tools down and let a professional finish the job.
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Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.
