Clutch Fluid — 3/90, P16 & 18
Look at the reservoir on the left handlebar. Is the slight window noticeable darker than the reservoir on the right handlebar (brakes)? Does your clutch seem sluggish or mushy? If the answer to any of these questions is yes, it's time to change the fluid for the hydraulic clutch on your Venture.
Some of you may wonder why the clutch fluid gets dark and looks burnt when it's DOT3 brake fluid, while the brake reservoir never looks dark or burnt. Because the slave cylinder for the clutch is mounted in the engine case itself, it takes much more heat than the brakes do and actually starts the deterioration process much more quickly. The fluid gets hotter much faster and starts to thicken up more speedily than if it were subject to usage in the brake system.
With the brakes out in the open on a bike, the fluid gets a chance to cool between uses, where the clutch system is constantly hot as long as the engine is running. Abuse on the clutch system is multiplied several times when pulling a trailer or sidecar, as many of us do.
That is why it's smart to change the clutch fluid when the color has turned very dark. You get a chance to flush some of the garbage out of the system and prolong the life of your clutch. I, personally, change the fluid in our bikes at the beginning of every riding season so it doesn't get that band and build up varnish and sludge in the hydraulic system.
The first thing to do is center-stand the bike and remove the left side panel and the plastic cover below it. Then cover the bike to protect paint, making sure that every area than can be splashed with brake fluid is covered. DOT3 brake fluid makes an excellent paint remover and also distorts and discolors most plastics, so cover as much as possible with a piece of plastic or vinyl. Brake fluid will soak through rags so stay away from them.
Now find the rubber cap located on the left side of the engine case, rearward and to the left of the rear cylinder. Remove this cap and you will see a bleeder screw. This is the screw to bleed the clutch slave cylinder, the area where the fluid takes the most heat and builds up more varnish and gum, which causes the dark color.
Next, slip an 8mm wrench over the bleeder screw, allowing room to move the screw in either direction. On the top of the bleeder screw, attach a piece of vacuum hose and route it into a container. The hose must fit snugly over the bleeder screw so no fluid escapes. I would suggest using a clear container or bottle and use a clear piece of hose so that you can see when the fluid is clear and not the old, dark fluid (see Picture. (See article).
Now you're ready to flush the system. Pump the clutch lever once or twice and hold it in. While holding it in, open the bleeder screw and leave it open until you feel no more resistance, or until the fluid stops coming out of the bleeder screw. While still holding the clutch lever in, close the bleeder screw. If you release the clutch lever while the bleeder screw is open, you will pull air into the hydraulic system, which you don't want to do! Repeat the above procedure until the fluid leaving the bleeder screw is clear, frequently checking the master cylinder on the left handlebar to make sure it isn't empty. You will have to fill this a couple of times during the process of flushing the system. If your fluid was real dirty, you will have to do this more than someone whose fluid was reasonably clean.
After you're done and the fluid coming out is as clean as the fluid you're adding, reinstall the side panels and make sure the fluid in the clutch master cylinder is between the marks on the sight glass. After a short drive around the block you'll notice the difference in the way your clutch works. You also might be preventing a clutch failure on the road.