Air Filter Servicing

As tough as modern-day plasma, ceramic or chromed cylinder coatings might be, one thing more than anything else will destroy an engine’s piston and rings, while also shortening the lie of the cylinder coating. That one thing would be poor air-filter maintenance.

The piston and rings are always first to suffer after an engine has been ‘dusted’. The term dusted refers to engine damage caused by dust or grit entering the engine, usually through the air-filter. Dust rapidly wears out the piston and rings, which causes a massive loss of compression and power. A dusted engine is usually very easy to kick over, but can be hard to start and will definitely suffer a lack of power.

Repairing a dusted engine, be it a two or four stroke, is quite simple. It usually only requires the replacement of the piston and rings. Modern-day plated alloy cylinders can usually withstand several dustings before a new cylinder is required. Older cast iron liners can be rebored after a dusting. Now it’s important to establish where the dust entered the engine to stop it happening again. Usually it’s the air-filter. A filter can only trap so much dust. Once the filter is completely full of dust and the oil is dried out, engine suction will draw grit through the filter into the engine.

Check your filter after every ride. If overly discoloured by dust it should be washed and re-oiled. It would be very unusual to expect more than two even slightly dusty rides from a filter without cleaning.

  1. Using rubber gloves, gently wash the filter element in turps or kero. This is to remove old oil and some grit. Washing a filter element in petrol will damage the filter over time. So be sure to use turps or kero. Now, don’t leave the filter soaking in the solvent. Instead quickly and gently squeeze out the turps or kero and then pat dry with a cloth.
  2. To get the most of the remaining unseen fine dust particles out of the element, wash it with warm soapy water. Massage the soap well through the filter. Then wash and rinse it in a bucket of warm water several times over. Then finally rinse it in warm water. After that, gently dry the element with a clean cloth, then leave it to stand in the sun for a couple of hours to fully air dry. Don’t be tempted to dry the element with a hair dryer, as overheating will damage the foam and the glue holding the element together. Try to always have two clean and oiled filter elements for each ride. That way you start the day with a clean filter in your bike, and then can swap to the spare element partway through the day if conditions are really dusty. Carry the spare element in a zip-top plastic bag.
  3. When the element is totally dry, it’s time to re-oil it. You should wear rubber gloves for this step. Most filter oils are coloured so you can check for even coverage. Pour a little oil on the filter and then massage it throughout. Keep adding oil until the coverage is complete. With one hand squeeze out what you can. This will leave just the right amount of oil on the element. Massage it again to ensure even coverage and there, you’re done. The final step is to reinstall the element in the airbox, where there are two schools of thought on greasing the seal face prior to fitting. It would have to be a very damaged filter seal face that would require grease to seal it. With some tight fitting airboxes, such as those on Yamaha WR’s, the grease will end up everywhere but where you want it! So it’s your choice whether or not you use a light dab of grease to help seal the element against the airbox.
  4. Air-filter manufacture Twin Air offers this handy filter cleaning kit that helps make the normally messy job of cleaning and oiling filter elements a whole lot tidier. It come with all the gear you need, and is available at leading dirtbike shops everywhere. It’s definitely worth checking out.

Fitting Alloy Bars

If your bike id fitted with standard steel bars, and they’re not bent, give yourself a wrap! You should go out and buy a lottery ticket – because you’re damn lucky! Manufacturers fit steel bars as standard because they’re cheap. It helps to keep production costs down. Unless you buy a KTM – they’re the first factory to install decent alloy Pro-Taper style bars as stock equipment.

There’s a gaggle of alloy handlebar brands available today, but brands like Renthal and Star are amongst our favourites. The bars are available in a variety of bends and styles, but best of all they are stronger, lighter and more comfortable than the stockers. They’re a must-have investment for any dirtbike rider, and best yet, they’re simple to fit.

  1. Start by removing the throttle tube, levers, brackets and grips from your stock bars. It pays to slide the throttle tube off the bar end, that way you don’t have to undo the throttle cables, which can be tricky on four-strokes with push-pull cable arrangements. Then remove the bars from the bar mounts, taking note of the way the bar mount clamps are installed. On some bikes they have to go back on the same way. Then place your new bars in position and lightly tighten the bar mounts. With the bars in place, refit the throttle tube, levers and brackets. When you get your bars adjusted correctly, use a felt pen to mark the position, that way you can always locate your bars again the future.
  2. Always use rings spanners or sockets when adjusting the bar mount bolts. Open-end spanners won’t give you enough tension and will often wind up rounding of off the heads of the bolts.
  3. Renthal grip glue makes fitting new grips a breeze. Follow the instructions on the pack and the grips will slide on the bars with ease, then when the glue dries, they stay firmly in place. Use the glue sparingly on the throttle side however! Too much glue can cause the throttle tube bar to stick against the bar or throttle housing, which could lead to a nasty surprise at the end of a fast section of trail! You can then wire the grips in place if you want added security.
  4. A little known tip is to use a work layer of plumber’s Teflon tape around the bars where the front brake and clutch perches mount. That way the levers can rotate on the bars in a crash, rather than snapping the levers.
  5. Once all your levers and grips are in place, refit your Barkbusters or brushguards which are a must for any serious dirtbike rider. Another handy tip is to spray the bar end mounts of the brushguards with WD40, which will help to prevent them seizing up inside the bar over time. If you just use plastic handguards, make sure the bar ends are plugged before you fit your grips, to avoid the chance a puncture wound should you crash and land on the end of the bar. Most bars are supplied with a bar pad, so use it. It could just the save on some costly dental work should you crash and head-butt the bars.

Changing Wheel Bearings

Wheel bearings would have to be one of the cheapest replacement parts found on dirt bikes. However a damaged or collapsed wheel bearings can make a real mess of disc rotors, hubs and brake calipers. Even a slightly worn wheel bearing will cause rapid wear to disc pads and give the bike a nervous feel through corners.

To check for worn wheel bearings place the bike on a work stand, hold the wheel at the top and bottom and as you pull with one hand, push with the other. If you feel no slop they’re fine. But if the wheel rocks and you can feel slack on the axle, that means there’s too much movement and the bearings need changing.

It’s smart to replace the wheel seals whenever the wheel bearings are changed. Wheel seals help to keep out the muck that wears out bearings. Bearings can also be fitted with seals, commonly called sealed-bearings. Some manufacturers don’t fit sealed bearings as standard. While you can get replacement genuine bearings at your local dealer, it pays to note that bearings are usually cheaper at a bearing supplier. Buy them there and you’ll be able to buy sealed bearings, which will last longer over time.

Carefully follow these steps to change your wheel bearings.

  1. Start by checking for worn wheel bearings as described above. If the wheel rocks on the axle your bearings need replacing.
  2. Remove the wheel from the bike, take the axle out and them start by levering out the wheel seals with a large screwdriver.
  3. Some bikes have circlips under the seal. Remove these also.
  4. Most manufacturers use two bearings on the sprocket side of a rear wheel and one on the disc side. There is a spacer between the bearings. Use a long steel punch to knock out the one bearing on the disc side first. Tap the punch evenly from one side of the bearing to the other until the bearing comes out.
  5. With the first bearing removed the spacer will fall out. Now it’s easy to knock out the remaining two bearings. While it’s out, clean the spacer and thoroughly clean inside the hub where the new bearings will be fitted. Use a round file to clean any punch marks on the spacer.
  6. Start the re-assembly process by fitting the new sealed bearings on the sprocket side. Use a strong steel punch, being careful to knock the bearing only on the outer ring. It’s hardened steel, so you won’t damage it. Make sure the bearing stays square and goes in evenly. If it falls in too easily, remove it and apply Loctite to the hub and bearing. Knock the second bearing in on top of the first. Fit any circlips on this side. Now turn the wheel over and insert the axle in from the bottom, with the thread at the top of the axle. Slide the spacer down into the hub over the axle. Knock in the last bearing until it bottoms out. Fit any circlips on this side.
  7. Tap in the new wheel seals. Don’t smother the seals in grease just use a few drops of engine oil.
  8. Reinstall he wheel into the bike and make sure it turns freely before fitting the chain and tightening the axle.

Changing Ear Brake Pads

If you mostly ride in dry country with little mud, sand or creek crossings, chances are your brake pads will last for ages. If you don’t, then the rate at which your brake pads wear will be directly related to the amount of mud, grit and dirt you ride through. The stuff is hell on brake pads, because the pad is always wiping the disc clean, even when the brakes aren’t on. This action constantly wears the pad material down. Brake pads need to be changed before they wear right out. Running pads right down to the metal will damage expensive disc rotors and caliper components. Carefully follow these steps to change your rear pads.

  1. With you bike cleaned, place it on a workstand and loosen the rear master cylinder fluid cap – but don’t fully remove it. Place a cloth under the fluid reservoir, as some fluid may spill over here later. Then use a large screwdriver to slowly push the outside pad and piston right back into caliper.
  2. Remove the brake pad retaining pin, or pins, depending on you bike model. These can sometimes be very tight, especially if they weren’t lubed when previously fitted.
  3. Slide out the pads and any heat insulating material that is sometimes fitted on the back of the pads. Now check that the caliper slides freely on the float pins. If not slide the caliper off the pins, clean the pins and wipe a little ‘rubber’ grease on the pins before refitting the caliper. Brake rubber grease is available from auto stores like Repco. Now slide the new pads into position and insert the pin (or pins). Make sure the thread on the pins has been cleaned with a wire brush and wipe a little grease onto the thread before screwing in and tightening. Operate the rear brake pedal to pump out the piston. Once the pedal is firm, top up the fluid reservoir and screw the cap on. Spin the rear wheel and make sure the brake is operating correctly.
  4. Brake pad are available in various compounds made from various materials. Some work better in certain conditions that others. Check with your dealer when buying your brake pads.

Credit: Phil Gielis, Andrew Clubb