Cycle News - Archive Issues - 1980's

Dirt bike ~re~: Part 3 Finishing school By Tom Kolnowski "Part one, part two, part three - just how long will this thing go on?" you're asking. Relax. After completion of this segment, the final one-third of our series on prepping your new dirt bike, you will be given a license to break away from . . w~enchmg and nde, race or ot~erWIse thrash your mechamcal marvel. A few more hours of your free time is all that is needed to complete the job. In part two, which appeared in last week's paper, we dealt with front suspensions, wheels and brakes. Our main concern in this final installment will be the rear suspension and setting up the controls, followed by a collection of general pointers. Final fiddling 12 As was the case with the previous twO installments in this series, your first order of business when undertaking any sort of preparation will be a comprehensive cleaning of the motorcycle, followed by a clean and jerk maneuver to place the bike upon your work stand. Our first area of concern will be the rear suspension/wheel assembly - which is not always the cleanest area to work on. It would be a good idea to have a container of hand cleaner available to periodically remove some of the accumulated .grime from your hands. Begin by loosening the rear axle nut and chain adj usters. If snail cams are used, rotate them to take pressure off the axle. While it's possible to remove the wheel from most bikes without taking the drive chain off completely, a few minutes spent doing the task now will make the reassembly process go much more smoothly. Spin the wheel and bri!1g it to a StC?p when the master lInk IS located In the rear sprocket area. Wllh a flat blade screwdriver, pry the clip from its home position and remove the link. As a general rule, we prefer to use a new master link and clip when reinstalling the chain. Pull the chain free and hang in a clean place. With the exception of enduro machinery equipped with quick release wheel assemblies, you may have to remove the brake torque arm to allow for an exit of the wheel without a hitch. Now that everything is free, pull the wheel away from the swing. arm. Following the same procedures outlined in part two of the series for prepping the front wheel assembly, carefully stage a repeat performance on the rear. Set the wheel/brake combination aside. The swingarm pivot, which also serves as the rear engine mount on many bikes, is one of the key areas to pay close attention to. If a grease fitting has been installed by the manufacturer, this is the perfect opportunity to give your grease gun a bit of exercise. After lubrication, tighten the pivot bolt to the recommended value listed in your bike's owner's manual with a torque wrench. On single shock systems, grease fittings may also be found on the components which form the shock linkage. In the case of dual shock systems, while you will not have the complicated linkages, it still pays to apply a layer of grease to the pivot points on both ends of the shocks. Take care to replace the pivot seals so that they seat properly - dirt and grease is an unwelcome combination. Again referring to your owner's manual, set the shock spring preload to the standard value. On most single shock systems, you will have to tighten or loosen a threaded ring to adj ust the spring. The value given in that case will be the exact length of the installed spring, normally in millimeters, and taken with the bike on the work stand. Others, such as the Husqvarna ITC shock, have a circlip that fits into a numbered groove machined into the shock body. The same advice applies to external damping adjusters - make sure that they are set to the standard position. A numerical code or click stop system are among the more common designs in this area. Keep in mind that we are interested only in basic preparation at this time - actually tuning your suspension into the beSt possible condition is an entirely different game that we are not concerned with in this series. Along wi th the age of long travel rear suspension came chain rollers, tensioners and improved chain guide designs. Make a trip through all of the fasteners and bearings that are at the heart of your particular set-up. Do all of the rollers spin freely? If the answer is no, find a cure for the problem before you go on. Maneuver the completed wheel assembly back into the swingarm, and with any separate wheel spacers and the chain adjusters in place, slowly feed the axle through the wheel and out of the opposite side of the swingarm. Spin the axle nut into place by hand. If the brake torque arm was removed, reinstall it now. Thread the chain through the guides and rollers, bringing the ends together at the rear sprocket to allow for easier installation of the master link. Replace the link and its clip, making sure that the clip is fully seated before you continue. Proper chain tension is critical with today's suspensions, and again the best method for arriving at the optimum adjustment will be found in the owner's manual. As a general rule of thumb, a measurement of one and one-half to tWO inches of free play (see photos A and B), taken at the midpoint of the swingarm, will give a chain tension adj ustrnent that is in the ball park. If your swingarm is not equipped with scribe marks in the adjuster area, make measurements from the swingarm pi vottO the center of the axle to assure that both sides are in agreement. An alternate method is to get behind the bike and sight along the top row of chain - if the wheel is not properly aligned in the swingarm, you will notice a slight curvature in the chain. Tighten the axle when the adjustment is complete. Fasten the seat and tank into their respective positions if you haven't already done so. While nearly all tanks are equipped with filters within their pelcocks, we prefer to install a secondary form of insurance in the area with an in-line fuel filter. Select the transparent plastic type - after a few riding sessions you may be surprised at the amount of grit that makes its way past the primary filter. Secure the fuel line as needed to prevent any contact· with the cylinder head or exhaust pipe. Every moment that you spend at the helm of your bike will be with hands and arms attached to the handlebars. It makes good sense to get your bars and controls in the beSt possi ble condition. Begin with measuring the width of the bars - for motocross use a figure in the 31 to 32 inch range is good. Enduro work, especially where the trees grow close together, will normall y call for bars to be trimmed to 29 or 30 inches. For cutting the bars to size, a hack saw with a fresh blade is your beSt bet. After removing the throttle and left grip, measure out an equal amount from both sides of the bar and mark. After cutting, take a file and smooth out any rough edges on the ends of the bars - your grips will benefit in the long run. Grip selection is a personal thing mount whatever you find that works well. Try to steer away from those that are made of extremely hard material. The better grips are molded from softer compounds, and your hands will stay comfortable longer. To keep them in place, apply a coat of adhesive, such as Malcolm Smith Grip Stick. For an extra measure of protection we also prefer to safety wire the grips. Take care not to cut the grip when cinching down the wire (see photo C). Before tightening the throttle assembly to the bars, spray on a dose of silicone spray lubricant - nroer use chain lube in this area. Evaluate the posi tion of your bars. Are they tOO far forward in the triple clamps? By rotating them toward you a few degrees, you may find a much more comfortable riding position. Tighten the pinch bolts when you find the beSt arrangement. Carefully trace the rouringof clutch, brake and throttle cables. Turn the bars from left to right, watching all of the cables and making sure that there is no binding. A few cable ties may be necessary to keep them in their appointed places. Pay close attention to the front brake cable/oil line on enduro bikes to assure that the cable won't hang up on your instrumentation. If it does, an immediate wheel lockup, followed by an unscheduled crash is the likely result. There must be sufficient slack in the cable to keep it well above the danger lOne (see photo D). By this time, you have completed approximately 95% of the work needed before you're prepared for anything dirt riding may throw at you. What remains are miscellaneous tips and adjustments that may make your time in the dirt that much more enjoyable, so read on. Setting the shift lever to the most comfortable position will promote quicker and cleaner shifts. If your bike came with a rigid shifter, think about installing a folding unit (see photo E). Also adjust the height of the rear brake pedal, again setting it to a comfortable level. You may also want to grease the pivot point - the entire pedal assembly will have to be removed to do the task. Make certain that any seals or O-rings are back in place before replacing the assembly. The kick starter pivot is another potential source of problems - they are prone to jamming, particularly those which do not have a rubber boot over the joint. Maintenance usually does not require disassembly as long as you have an extension attached to the nozzle of a can of silicone spray. Simply direct a dose directly into the pivot. When adjusting the front brake, always begin by screwing the upper -adjuster all the way into the lever perch. Move down to the lower adj uster (see photo F), which is n,Qrrnally secured to the exterior of the brake backing plate or fork leg, and adj ust the brake properly - now you can take full advantage of the adjustment available at the lever perch. That may prove handy when the brake requires adjustment while you ;;ueriding, since you can do it while under motion. Leave approximately one-half inch of free play in the cable when you make your final adjustment (see photo G). The side panels on most bikes also serve as a heat shield to prevent the exhaust pipe from roasting the side of your leg. Take a quick peek behind the plastic panel and check to be sure

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