How To Modify - Feature

Modify Your Cruiser Motorcycle

Cruisers are more than simply rolling motorcycle art. They represent both a means of taking their owners places they've never been (physically and spiritually) and a canvas for the expression of a personal vision. While many cruisers may have a retro feel, the underlying technology is up-to-date. This sophistication may be intimidating to novice mechanics, who need a place to start their journey of bike modification.

How to Modify Your Cruiser Motorcycle is based on two ideas. First, most cruiser riders are by their nature tinkerers. They usually start with simple bolt-on goodies, like some chrome trim. Second, their interest in their machine brings them into performing basic maintenance which drives them toward more advanced modifications.

Following a similar progression, How to Modify Your Cruiser Motorcycle begins with the most basic maintenance projects and continues through major modifications, helping riders of almost any level of mechanical ability plan and carry out a variety of performance enhancements to their cruisers. The book's structure groups the projects into the various systems on a motorcycle. Each section begins with easier projects before moving on to more challenging modifications. For example, the engine section begins with installing an aftermarket exhaust system and ends with installing a big-bore kit. Other topics range from freshening brakes to fixing fork seals to installing aftermarket wheels and brakes to tuning EFI systems. Novice and experienced mechanics alike will find something to spark their interest in the book's 30 projects.

Each project starts with a table containing an estimate of how long the modification will take, the tools required, and the mechanical experience necessary to undertake it. The parts list makes sure that everything can be gathered prior to disassembling the bike. Every project includes a tip, highlighting a key consideration. Finally, a brief description of the expected performance gain is stated. Some projects also include a listing of any complementary modifications to be considered. You get the most vital information in an easy-to-digest format-all before reading the actual body of the project! The main text of each project takes the reader through in a step-by-step manner. Photographs highlight key points in the process.

Armed with this book and a factory service manual, just about anyone should be able to wrench his way from novice to experienced mechanic-and have a bunch of fun along the way. How to Modify Your Cruiser Motorcycle will be available from Motorbooks International, in bookstores and online vendors in time for Christmas. Although most cruiser enthusiasts will have to visit the book's official website ( to download free sample projects, Motorcycle Cruiser readers can now enjoy this sample project in a portable non-electronic form.

Project 9: Hydraulic Fluid Change
Time: 45 minutes
Tools: Wrenches, sockets, rags, torque wrench (inch pounds), Teflon tape, brake bleeding tool (optional), clear hose, glass jar for brake fluid, rags
Experience: 1
Parts: Brake fluid
Tip: Only use fresh fluid from unopened containers, and never mix fluid brands performance gain: Better lever feel, no nasty surprises
Complementary Modifications: Add braided steel brake lines

Maybe this weekend, when you needed to do a panic stop because a dog ran out in front of you, your brake lever came much closer to the grip than usual. Or maybe you just checked your brake's (or hydraulic clutch's) fluid and noticed that it has turned dark or cloudy. Or you could just be following your bike's maintenance schedule (good for you!) and the time has come to freshen your hydraulic fluid. However you came to this point, you should know that fresh hydraulic fluid is vital for proper performance.

Most hydraulic fluids have a taste for water and will gradually suck moisture past the rubber seals in your calipers. If your fluid is contaminated with water, heavy brake use will raise the temperature to the point where the water will boil (at a significantly lower level than pure fluid would), leading to brake fade and the dreaded lever-to-the-grip experience.

Cruisers should swap out hydraulic fluid at least once a season. Some people claim you should do this as part of the winterizing process, so that the moisture-free fluid sits in your bike all winter. Having never had problems develop while my bike was in storage, I prefer to flush the fluid at the beginning of the season so that I get the benefit of fresh fluid in the spring. Those whose priority is maximum braking performance will most likely want to follow this schedule, too.

The tools required for this project are minimal, but you can buy some specialized tools if you like-you know you want to. The Mityvac bleeding system (from Lockhart Phillips) is perfect for bone-dry systems-such as when you've installed stainless steel lines. If the system is already primed, an old jar and clear hose will work just fine. The fluid you add to your system should come from an unopened container. Remember the hydraulic fluid's thirst for water. Although DOT 5 fluids are silicone-based and, therefore, don't absorb moisture, some riders don't like the feel at the lever as much. Most OEs still recommend DOT 4 fluid. Also, make sure you buy a name-brand fluid. Buy more than you think you need. (If you're having trouble with bubbles in your lines, the best cure is to run plenty of fluid through the system to sweep them out.) Finally, never mix brands of brake fluids. If you need to top off the reservoir and don't know what type or brand of fluid is already in the system, flush the entire system to avoid any problems of interaction between the different formulations, even though-in theory-all DOT 4 (and DOT 5.1) fluids should play well together.

Begin with your bike on its side stand or a lift. Since brake fluid damages paint and some powdercoats, remove any vulnerable parts or cover them with rags. A preparatory step required for those using vacuum bleeders and optional (but recommended) for all others, is to wrap the threads of the calipers' bleeder valves with Teflon tape. Vacuum bleeders create so much suction that they will draw air into the system past the bleeder valves' threads, making it impossible to determine when all air has been removed from the system. Teflon tape fills the minuscule gaps between the threads when the valve is not completely closed and is a worthwhile modification to all calipers. One warning, though: Don't just remove the valve with the caliper mounted to the bike. Since the master cylinder is higher than the caliper, fluid will leak out all over the place, ruining your brake pads. Raise the caliper equal to or above the reservoir to keep the mess to a minimum. Of course, if your lines are empty-as when you've just added stainless steel ones-this is not a problem.

Rear calipers have their own idiosyncrasies to consider. Since the brake line travels horizontally from the master cylinder to the caliper, air bubbles are trapped in the line more easily. To assist bubbles in their travels, remove the caliper and hold it higher than the master cylinder, allowing the bubbles' tendency to rise to keep them moving as you run the new fluid through the system. If you're pumping the pedal, make sure you place a spacer between the brake pads to keep the piston(s) from popping out of the caliper.

When using a vacuum bleeder, you can save some time by sucking the excess fluid out of the master cylinder. Then wipe any visible grit out of the reservoir. If you're not using a vacuum bleeder, don't worry about running the old fluid through the system-unless you see dirt or other visible impurities. Don't add fresh fluid to the reservoir until most of the old fluid has been pumped out of it and into the brake system itself.

Swapping the fluid in the system is pretty easy. Put a box-end wrench on the caliper's bleeder valve, then press a length of clear hose over the nipple. This must have a snug fit. The other end of the hose should empty into a container that is capable of standing on its own. (Glass containers, while breakable, are usually heavy enough to stay put unlike plastic bottles or aluminum cans.) Slipping the hose through a hole in the screw-on cap is ideal. Don't forget to leave a breather hole in the lid, or the built-up pressure could pump the fluid out of the hose when disconnected from the nipple, creating another mess. (Don't ask me how I know this....)

Pump the lever a few times and hold the last squeeze. Using the wrench, open the bleeder valve until the pressure forces fluid into the hose. Hold the lever all the way in until you've closed the valve. Repeat this process several times until you have a couple inches of fluid in the hose directly above the bleeder. Now, open the valve slightly-only until you can just squeeze fluid out with the lever and no more. Continue to squeeze and release the lever until you see the fresh-usually clearer-fluid emerge from the bleeder. A short pause between every squeeze and release will make sure that any bubbles expelled from the system don't get sucked back in when you release the lever. Pay special attention to the reservoir while you are pumping the fluid through the system. If you let it run low, you'll introduce more air and have to start the bleeding process from scratch. If you started with empty lines, plan on running several additional ounces of fluid through the system after you stop seeing bubbles to make sure that none remain.

When you're sure that the hydraulic system is free of old fluid and/or bubbles, slowly squeeze the lever as you tighten the bleeder valve. Pump the lever several times and hold. Open the bleed valve to release the fluid. Do this several times. You'd be surprised how often one last bubble pops out during these final, high-pressure bleeds. If one does, run a few more ounces of fluid through the system. You will be rewarded with firmer lever feel. Torque the bleed valve to the recommended spec and finish by topping off the reservoir. Don't forget the other caliper! Make sure that the rubber diaphragm on the master cylinder is clean before placing it on top of the hydraulic fluid and tightening down the reservoir cover. Wipe away any traces of the brake fluid before it has a chance to damage any painted surfaces. Finally, as with all waste fluids from your bike, be a good citizen and recycle the old stuff.

Those of you with vacuum bleeders shouldn't feel left out. All of the steps are the same, except that the fluid will be sucked from the bottom end of the system instead of forced from the master cylinder. The same cautions apply, though. Accidentally let the reservoir go dry, and you'll need to start over. Just keep pumping the bleeder to maintain a constant but not excessive pressure. When no more bubbles present themselves, you're done.

Any discussion of hydraulic system bleeding usually includes a debate about which method is better: the master cylinder push-through or the vacuum tool suck-through. While many mechanics will subscribe to either one or the other, I've found a combination of the two works best. When bleeding dry lines, nothing gets them primed quicker than a vacuum bleeder. However, when swapping fluid, I prefer the pump-through method. So, when installing new lines, I use both methods. First, draw the fluid through with a suction tool, followed by the final flushing of air with the master cylinder pumping method. Regardless of which technique you incorporate, the goal is to fill the system completely with fresh hydraulic fluid and no air bubbles. You'll be glad you did this the next time you grab a handful of brake.