Motorcycle MaintenanceMotorcycle Maintenance
One of my hobbies is riding and restoring, and maintaining motorcycles. I've not been trained to do it, but I learn as I go, and I enjoy learning things as I need them, so I've decided to share what I know. This collection will start out small, but will grow as I photograph more aspects of maintaining a bike.
My favorite bikes are Yamaha Maxim family bikes from the early to mid 1980's so most of the pictures used here will be of those bikes, but most of the information will be more generally applicable.
Flushing hydraulic brakes (vacuum method)Flushing hydraulic brakes (vacuum method)
Brake fluid reacts with air and water and needs to be changed on a regular basis. I change my fluid once a season, and recommend the same, but in all honesty, changing it once every three or four seasons probably will not result in failure. If your brakes are sticking, it's time to change the fluid. The most common methods for home for bleeding brakes at home is the pumping method. Here I will describe another method known as the vacuum method. The advantages of the vacuum method are that it is faster, easier, and can be used on an empty brake line. The disadvantage is that it requires a vacuum pump.
You will need:
- Brake Fluid
- Screw Driver Set
- Wrench Set
- A friend who is willing to help
- Vacuum Pump (example)
As preparation, remove or cover any nearby painted surfaces to prevent brake fluid from dripping onto them. I always remove my gas tank. Brake fluid is very corrosive to paint.
Remove the lid from your master cylinder, wipe it off thoroughly, and set it aside in a clean place. Use the pump to remove any old brake fluid. When the master cylinder is empty, wipe it clean inside and, if necessary, clean out any hardened old brake fluid until it looks nice and clean inside. Finally replace the old fluid with clean new fluid that meets the specifications for your bike. the required fluid is stamped on the lid of the master cylinder. Most bikes that are still on the road will require at least DOT3 fluid.
After your master cylinder is refilled with new fluid, you can get set up to start the pumping. Place a wrench on the bleeder valve but do not turn it yet. As always, be sure to use an appropriately sized wrench rather than an adjustable wrench, something almost right, or god forbid pliers. It will not be worth the time you saved when you round off the bleeder valve.
Once the wrench is in place, you can connect the vacuum pump as described in its manual. My pump has a canister that sits in the middle of the line as shown.
Be sure to read and understand the rest of this post before attempting any actual pumping. Now we're ready to actually start pumping. Squeeze the handle on the vacuum pump a few times (or turn it on if you have an electronic pump). Once there is vacuum in the line, turn that wrench about a quarter turn to open the bleeder valve. At this point old fluid will flow out of the line into the vacuum bottle, and new fluid will replace it from the master cylinder. It is critical that no air flow into the line from either end of you will have to start over. This means you (and your friend will have to monitor two things.
- The vacuum on the line must never reach zero
- The fluid level in the master cylinder must never reach the bottom
One person can continue pumping as the other person continues adding fluid the the cylinder. Once clean fluid starts to come out of the line, you can re-tighten the bleeder valve, and then release the vacuum.
If you have a dual front brake system, you should repeat the process for the other disc. The second side should go faster as the top of the line is already flushed, and only the bottom needs to be done. If you only have a single disc, then you are almost done.
After you've flushed the entire line (two sides or just one) all that is left is filling the master cylinder back to the level indicated by the level viewing window.
That's all there is to it. It should take about an hour and a half your first time, and closer to an hour subsequent times. Be sure to thoroughly test the system before riding.
Replacing a master cylinder's viewing lensReplacing a master cylinder's viewing lens
Most bikes use a hydraulic system for the front, or both front and rear brakes. My XJ700 uses a dual-disc hydraulic system for the for the front wheel only. Maintaining the specified level and quality of brake fluid in the master cylinder for such systems is critical, so there is almost always a clear plastic window in the side of the master cylinder that allows you to monitor the fluid level and color. Unfortunately, as bikes age, these windows become hazy and cracked which makes monitoring the fluid impossible. Eventually the window may even start to leak. Luckily, it is pretty straight-forward to replace and old window with a new glass one that looks great and doesn't leak.
You will need:
- New Lens
- Screw driver
- RTV Silicone
- Precision Knife
- Aerosol brake cleaner
My lens was so old that it started leaking. You can see that the leaking brake fluid eroded some of the paint from the outside of the master cylinder. It got bad enough that I accidentally punched a hole right through the lens with my bare finger. It is not uncommon for old bikes to have lenses like this, but replacing them is so easy that I will never let mine get like this again. The first step in this process is to remove the master cylinder cap and empty out any remaining brake fluid either with paper towels or a vacuum pump.
Next, dig out the old lens in chunks. I used a flat tip screwdriver for this, but pretty much any tool will do. There is really no reason to try to keep your old crusty lens in one piece, so just chip away at it. If your bike has a chrome trim or other metal ring around the lens, leave it in place. You can see that mine has a metal ring around the hole and a back plate. This is a pretty common design, and you will want to leave it in place.
After you have most of the plastic removed, you can get out a precision knife such as an X-acto to clean out the rest of the small plastic chunks, hardened brake fluid, gasket, and any other crud that has built up around the lens. Take your time, and get all of this out thoroughly because if you don't your new lens will be leaking in no time.
When you have all the debris removed from the area clean it with brake cleaner, and wipe it down with a paper towel several times, then let it dry for several minutes. When you are done with hole should be impressively clean, possibly even new looking.
Now you are ready install the new lens. Read and follow all of the instructions on the packaging of your RTV silicone. Sparingly apply a ring of silicone around the outside of the lens or the inside of the hole in the master cylinder. Quickly seat the lens in place making sure that the silicone seals the joint all the way around the circumference of the lens. The silicone will skin in less than 30 minutes, but will not dry to full strength for 24 hours. Let the silicone dry over night and then refill and flush the brake system.
The process is pretty straightforward, and not counting the drying time, it should take a little over an hour. Obviously you will want to thoroughly test the system to be sure it is safe before any real riding.