Bleeding Bike Hydraulics


This isn't maintenance that's limited to Vulcans or even Kawasaki's in general. If you've ever changed your brake fluid (recommended every year to remove moisture and other contaminants) in your clutch and brake lines you know it can be a chore.

Most of us just connect a hose to the bleed screw and pump away on the levers (and pump, and pump and.....) until only new fluid is escaping. Well, there are simpler ways. 

The very best is to purchase a $30 (or so) vacuum pump made for the purpose called a Mity-Vac .  /files/includes/images/mity-vac.jpg (114136 bytes)This allows you to easily draw the fluid down through the master cylinder reservoir and out the bottom of the hose whether it's brakes, clutch or any other fluid.  Mity-Vac's are available in the aluminum with impact resistant vacuum gauge as shown at left for heavy duty use or for a 'lot' less money in plastic with just an ordinary metal gauge.   For most of us the plastic ones will work just fine.   They've available at some auto supply outlets and at Harbor Freight among other places.

To use the Mity-Vac you remove the cover from your master cylinder reservoir,  attach the tool to your bleeder valve with clear plastic hose (supplied with tool) and pump the lever a few times.  The gauge will show vacuum.  When the needle gets somewhere around 30 psi open your bleeder valve (be sure you have someone ready to pour fresh fluid in the reservoir) and watch the old fluid pour through the hose and into the Mity-Vac container.   You might have to do this a couple of times to remove all the old fluid.  When the brake fluid coming out the hose is the same color as the fluid being poured into the reservoir you're finished.  Close your bleeder screw, wipe off any excess brake fluid and ride.

Another less expensive method has been suggested by (Idaho) Tim Patterson.  It uses exactly the same principal (suction) without the expense.

Go to a feed store or Vet supply and get one of their largest Syringes. This should not cost more that a couple of bucks.  The one shown at right is a large 12cc 'irrigation syringe' that costs about a dollar.  Use clear plastic tubing (available at any automotive store) that will slide onto the syringe and onto the brake or clutch bleeder valve.

Open the valve a turn and a half, take the top off your brake fluid reservoir and draw back on the syringe. This will suck the fluid and air bubbles into the syringe. Be sure to keep checking the reservoir, you don't want to empty it out and start drawing air into the system.

Tim bled all 3 brake cylinders and his clutch in about 15 minutes this way. If the syringe is full and you want to bleed more, just kink the hose so no air bleeds back, detach the syringe and squirt it into a can. Re-connect and do it again.


How To:

One question that crops up often among Vulcan owners is "where is my clutch slave cylinder?"   or "where is the bleeder for my clutch".    /files/includes/images/clutch_slave_cyl.jpg (61676 bytes) Answer, it's under the left side engine cover.  Remove the cover and look for the silver object as shown in the photo (right).  Notice the bleed valve is right on top, the hose from the clutch comes from the bottom rear (on Nomad anyway).  

After bleeding the clutch be sure and rinse any fluid that gets on painted surfaces off with lots of fresh water.   Brake fluid will remove the paint and rust will form very quickly on the surface.

Whether you're using the Mity-Vac or Tim's Syringe or you've decided to do it the way dad did, pumping the lever with a clear plastic hose emptying from the bleeder screw into a container of brake fluid the objective is the same.  Replace the old fluid with new.

Always use the brake fluid recommended by the manufacturer.  It's usually stamped right on the master cylinder cover.  If not it's in your owners manual.  For Vulcans it's DOT 4.   Use a fresh sealed container of fluid, not leftovers in an opened container that's been on a garage shelf for several months.

Have someone help you make sure the master cylinder reservoir doesn't go dry while you're sucking fluid out the other end of the hose.  If it does you'll just draw a lot of air into the brake/clutch system and will have to work much harder to evacuate all of it.

When the fluid coming out the brake caliper or clutch slave cylinder end is the same color as the fluid going in and there are no air bubbles you're finished.  Tighten your bleed screw, make sure you haven't spilled any brake fluid on a painted surface (it's one of the greatest paint removers ever made) and pump your brakes/clutch a couple of times just to make sure the levers are nice and firm.   If they're squishy you've gotten air into the system so bleed some more.

Have a firm lever?  Go ride!