ST1100 Maintenance Tips

Flushing or Bleeding the Brakes and Clutch

The first procedures, flushing the system, assume that you haven't got air in the system. Flushing the system cleans out the old, contaminated, brake fluid. Per my ST1100 owner's manual, this procedure should be done every two years or 12,000 miles, whichever comes first. Brake fluid is hygroscopic, and absorbs moisture from the atmosphere. Over time, this moisture will lead to a significant reduction in the boiling point of the fluid and to corrosion of the internals of the brake system. That's why the fluid should be changed regularly.

If you have disassembled a caliper or master cylinder, changed brake lines, etc., you have air in the system, and you will have to skip to the later sections on bleeding the systems.

Tools and supplies

Number 2 Phillips screwdriver for the reservoir cover attachment screws.
Wrenches for the bleeder screws - size 8mm and 10mm.
Allen wrench for lower fairing removal - size 5mm.
A foot or so of 3/16" clear vinyl tubing
Old glass jar for capturing the waste fluid.
Turkey baster or like device.
Supply of fresh DOT-4 brake fluid.
Clean, lint-free rags.

Flushing the clutch system for all models.

Remove the lower fairing to gain access to the bleeder on the clutch slave cylinder. You will find it on the front face of the engine, above the oil drain plug.
Use a towel or some rags to cover and protect the top shelter and fairing from any brake fluid splatter.
With the bike on the centerstand, remove the cover from the clutch master cylinder.
With your turkey baster, suction all the fluid from the master cylinder reservoir. Wipe the remainder of fluid out of the bottom of the reservoir. Clean up any muck that you find there and on the sight glass. Make sure you don't deposit any lint into the reservoir while doing this.
Fill the reservoir with fresh DOT 4 brake fluid.
With the box end wrench (or a hex socket), momentarily open the bleeder screw on the clutch slave cylinder only about 1/8 turn and then close it. In case the screw has partly frozen in place, this will prevent damage to the hex on the bleeder screw. Attach the vinyl tubing to the tip of the bleeder screw, and put the other end into your waste jar.
Open the bleeder screw and make one full stroke clutch lever application. DON'T RELEASE THE LEVER YET. Hold the lever in the applied position and have a helper close the bleeder screw. Release the lever while the bleeder screw is closed. Repeat this step once more. This process forces all the contaminated fluid from the master cylinder bore.
Note: If you don't have a helper, and your arms aren't long enough to enable you do do this alone, wrap several stout rubber bands around the handlebar and clutch lever. This will make the application and holding the lever applied automatic. Then open the bleeder screw to allow the fluid to exit. Close the bleeder and pull the lever away from the handlebar. Repeat the process.
Remove the rubber bands from the clutch lever, so the lever will return to the resting postiion. Open the bleeder screw on the slave cylinder about one full turn. Gravity will allow fluid to flow through the system and into the waste container. Keep an eye on the fluid level in the reservoir. Do not let the reservoir get empty! If it gets empty, you will get air into the system which adds a lot of grief to your life, and you will have to bleed the air from the system. (See last section.) Keep topping it up and watch the color of the fluid draining into the jar.
When the draining fluid looks clean, close the bleeder screw.
Fill the reservoir to the upper level mark (see owner's manual) and replace the cover.
Wash the areas where you may have got brake fluid spread. Brake fluid is a pretty effective paint remover if you don't clean it off.
Install the lower fairing.

Flushing the brakes on all ST1100 standards and 1990-95 ABS.

The procedure is essentially the same as flushing the clutch except:

A few obvious things, such as you don't have to remove the lower fairing, you remove the right hand side panel to access the reservoir for the rear brake master cylinder, etc.
Flush the right front caliper before flushing the left front.

Flushing the brakes on all ST1100 ABS-II (1996-2002).

Since the linked brake system on the later model ABS bikes incorporates a secondary master cylinder, delay valve and proportional control valve, I don't believe it's possible to achieve a brake system flush using gravity flow as in the previous sections. It is necessary to do a brake system bleed as described later, although it will be a lot easier not having to get air out of the system.

Bleeding the systems.

If your brake or clutch system has air inside the hydraulic circuits, it won't function properly. The procedure is much like what is outlined in parts of the flushing procedures.

Bleeding the clutch system.

Remove the lower fairing to gain access to the bleeder on the clutch slave cylinder. You will find it on the front face of the engine, above the oil drain plug.
Use a towel or some rags to cover and protect the top shelter and fairing from any brake fluid splatter.
With the bike on the centerstand, remove the cover from the clutch master cylinder.
With your turkey baster, suction all the fluid from the master cylinder reservoir. Wipe the remainder of fluid out of the bottom of the reservoir. Clean up any muck that you find there and on the sight glass. Make sure you don't deposit any lint into the reservoir while doing this.
Fill the reservoir with fresh DOT 4 brake fluid.
Actuate the clutch lever while watching the fluid in the reservoir. One or more small bubbles may float to the surface. If so, you need to repeat this action until the bubbles stop appearing. Note, it may take many dozens of applications. The applications don't have to be full stroke. A partial stroke is all that's required.
When the bubbles cease to appear, the master cylinder is bled.
With the box end wrench (or a hex socket), momentarily open the bleeder screw on the clutch slave cylinder only about 1/8 turn and then close it. In case the screw has partly frozen in place, this will prevent damage to the hex on the bleeder screw. Attach the vinyl tubing to the tip of the bleeder screw, and put the other end into your waste jar.
Open the bleeder screw and make one full stroke clutch lever application. DON'T RELEASE THE LEVER YET. Hold the lever in the applied position and have a helper close the bleeder screw. Release the lever while the bleeder screw is closed.
Note: If you don't have a helper, and your arms aren't long enough to enable you do do this alone, wrap several stout rubber bands around the handlebar and clutch lever. This will make the application and holding the lever applied automatic. Then open the bleeder screw to allow the fluid to exit. Close the bleeder and pull the lever away from the handlebar.
Continue repeating the process. Keep an eye on the fluid level in the reservoir. Do not let the reservoir get empty! If you do, you will get air into the system and you are back to square one. Keep topping it up and watch for the presence of bubbles in the fluid draining into the jar.
When the draining fluid shows no more bubbles, close the bleeder screw.
Fill the reservoir to the top of the sight gauge and replace the cover. Remove the rubber bands.
Wash the areas where you may have got brake fluid spread. Brake fluid is a pretty effective paint remover if you don't clean it off.
Install the lower fairing.

Bleeding the brakes on all ST1100 standards and 1990-95 ABS.

The procedure is essentially the same as bleeding the clutch except:

A few obvious things, such as: you don't have to remove the lower fairing, you remove the right hand side panel to access the reservoir for the rear brake master cylinder, etc.
Bleed the right front caliper before bleeding the left front.
Tip: Periodically tap the brake caliper you're bleeding with something like the plastic handle of a screwdriver. This will shake loose any of the small air bubbles which may be adhering to the caliper internals.

Bleeding the brakes on all ST1100 ABS-II (1996-2002).

Same as above, except a different sequence is required in the procedure. This is as follows:

Left front caliper upper bleed valve, using the front brake lever.
Right front caliper upper bleed valve, using the front brake lever
Left front caliper lower bleed valve, using the rear brake pedal.
Right front caliper lower bleed valve, using the rear brake pedal.
Rear caliper front bleed valve, using the rear brake pedal.
Rear caliper rear bleed valve, using the rear brake pedal.