Editors Note: This is the first installment in a series of basic dirt bike theory and maintenance. This series will cover the entire workings and maintenance of the 'universal' dirt bike. No specific make or model is used as a model.

We have to make a couple of statements here. First, you need to heed all safety precautions. Wear the proper personal protective equipment for the job. Invest in a good pair of safety glasses. Second, this series is not meant to replace a good Service Manual for your particular model. If you are going to do any maintenance that is not covered in your Owners Manual, you will save yourself a lot of time and frustration by procuring the proper Service Manual for your bike.

We hope that you will find this informative whether you are a brand new dirt bike enthusiast, or a grizzled veteran.

Mark is interested in feedback from you. Please reply to Tuner at dirtbike@off-road.com.

OldFart

Wheels!

I was wondering what subject would be good to begin with and figured I'd start with wheels. I mean, heck, that's the first thing into a section, mud hole, finish line, wreck and just about anything else that involves forward movement.

Wheels are generally round for good reason. When they aren't, life can suck. Wheels get their structural integrity from the spokes, obviously. But for most situations, only about half the spokes are doing any work. These would be the ones that are on the top half of the wheel at any given time. The weight of the bike is pulling down on the few that are positioned basically over the axle. In other words, the only real strength spokes have is tensile (pulling) strength.

Rims are all basically the same but with some minor differences in older ones. Years ago rims were made from steel with a nice (sometimes) layer of chrome on them. These were weak and prone to bending and breakage. Next came the shouldered rim. These were heavier and a little stronger but still not very strong for hard riding. Then came alloy rims. Lightweight AND strong. Life was good. Now most production rims are adequate for most recreational riders. Faster people will end up replacing their bent/cracked rims with good aftermarket parts. Spokes can be improved on also. There are heavier gauge stainless steel spokes available for a little more than stock spokes. These can help handling. How much depends on how wimpy the stock spokes were.

Hubs are where the bearings live. This is also the beginning end for the spokes. Older hubs were of some unusual shapes. They started out pretty much flat all the way across since they had to hold the brake shoes and drum also. In the quest for lighter weight, out came conical hubs of a variety of designs. Now with the advent of disc brakes, they also hold the rotor nowadays. Most current day hubs are more than adequate if the spokes are kept properly tightened. For those moto-maniacs that need something stronger, there are a few aftermarket hubs available.

Tires are a big variable. There are more brands and types available to keep even the most experienced guessing at which is the best for any given circumstance. I used to think there were a few basic rules for tire manufacturers but the more I looked for rules, the more I realized there really weren't any. Knobby tires come in a variety of rubber compounds and knob patterns. Picking the best tire can be a little tricky. Asking someone familiar with the terrain can be a good direction to turn as long as they have an open mind about tires. Some people are as blind to tire brands as they are to bike brands. I know many successful racers who are "strictly Dunlop" or "strictly Bridgestone" or whatever. I've had good experiences with the Michelins for the type of riding I do and the terrain I ride in.

Front tire size is pretty much a no-brainer. Rear sizes can be a little misleading depending on brands. Be sure to compare apples to apples when price shopping/ordering. For instance, a Michelin rear 120mm width tire is the equivalent to a Dunlop 100mm width tire. Don't think bigger is better for a rear tire either. Putting too big of a tire on a 125 can bog the motor down quite a bit. The bike manufacturer generally had a good handle on this when they put the size tires on your bike that they did.

Hope you got something out of our first article. Be sure to check out the Maintenance section too.

Maintenance

We know what the wheels do, now lets look at trying to keep them in good working order.

Some out of roundness can be reduced/removed by adjusting "key" spokes. The position of the "key" spokes is determined by the deformation. A dent in a rim cannot be removed by truing with spokes. Truing wheels is almost an art form.

The wheel can be trued on or off the bike. If you're trying it on the bike, be sure to push the brake pads away from the disc so the wheel turns freely. If you have the wheel off the bike, tighten the axle in a vise with it sticking straight up. Now the wheel can be set on the axle and spun like a vinyl record (remember those?). You can take a magic marker and just hold it steady near the rim to mark high (or low) spots. This can help pinpoint the deviations. Make spoke adjustments in small increments. A little adjusting can make a relatively big change.

For lateral runout (the sides to side wobble as viewed from in line with the wheel) the spokes on the "outside" of the runout need to be loosened and the spokes on the inside need to be tightened. Depending on how big the deviation is determines how many spokes in a row need to be adjusted. What you need to do is pull the rim towards the center (remember we're speaking about side to side) by tightening and loosening spokes at any given point. Loosen the spokes on the side that the rim is "away" from the center and tighten the ones that are "towards" the center, pulling it closer to the correct centerline.

For axial runout (up and down movement) let's say the flat spot is positioned at 12:00. You would loosen the spokes at the flat spot. Then you would tighten the spokes to the sides of the flat spot, roughly in the 10:00 and 2:00 areas. This varies from the size of the deviation. If the rim is dented, it is next to impossible to correct.

Lacing a new rim isn't quite as bad as one might imagine. An extra person will come in handy when trying to get the first spokes in their respective holes. Begin by starting the nipples on the spoke about halfway down the threads. The main thing is don't go too far and use a reference mark (a certain amount of exposed threads works well) so you can get them all equal. Once all the spokes are started, go around the wheel tightening them a few revolutions each until they are starting to get near the point of getting tight. This is the hard part. You need to start spinning the rim to check for deviations. Correct by tightening the appropriate spokes. Keep going until they are all tight. Sounds easy, huh? Even for the experienced, it isn't. If someone tells you it is, they are lying.

Some people use the "tuning fork" method of tightening spokes. As long as I don't have any nipples that aren't difficult to turn, I go by how much effort is required to turn the nipple. If they are seized, this method doesn't work very well. A little squirt of WD-40 after washing your bike goes a long way at preventing problems down the road. The tuning fork method involves tapping the individual spokes and listening for a nice tone or a dull thud. A dull thud indicates a spoke isn't tight enough. The only problem with this method is when you get bent spokes applying force to the spoke next to it and affecting its tone. This is also a "learned" feel type of thing.

Some people like to tie wrap or safety wire the spokes together where they touch/cross. I've seen this on a lot of desert bikes. This pretty much renders the tuning fork method useless unless the spoke in question is quite loose. When we ran the Vegas to Reno desert race we did break one rear wheel spoke, maybe due to not wiring them.

Now we've got a (hopefully almost) round wheel. Make sure the axle has a light even coating of waterproof grease and put it back on the bike. Check your manual for proper torque specs. Axles normally need to be pretty darn tight. The right side fork leg (right when sitting on the bike) has a couple pinch bolts (or nuts). Do not tighten these yet. These will be tightened very last. Put the rest of the stuff back on (caliper, disc guard, etc, etc) and pump the brakes to seat the pads against the disc. Take the bike off the stand. Grab a big handful of front brake and compress the forks as hard as you can. This will make the right fork leg find its unstressed position on the axle. NOW you can tighten the pinch bolts. If this step is not done, you may run into a situation where the forks can bind as they go up in their travel.

Now we have everything all bolted together ready to ride. Did you check the wheel bearings? No? Put the bike back on the stand. Grab the tire right at the point it goes between the fork tubes. For the rear wheel, try moving the wheel where it goes between the swing arm. Move it side to side. There should be no perceptible play. If so, you may need new wheel bearings.

Replacing wheel bearings is pretty easy if you have a big hammer. If you try it with too small a hammer, all you're going to accomplish is pissing off the bearings and yourself. A long chisel is also necessary. I have a nice Snap-On automotive wheel bearing race chisel. This is about 18" long and has a slightly rounded tip on it. Very nice for motorcycle wheel bearings. Remove any dust seals by gently prying with a wide tipped screwdriver. Inspect these seals. These can let water in which can ruin your bearings. You may be able to get away with reusing these. Remove any bearing fasteners. Bike manufacturers will use anything from nothing to a screw collar. Snap rings are among the most popular. Sometimes the screw collar will have a "peened" spot that needs to be drilled out before removing or the screw collar can be ruined during the removal process.

Now you have exposed bearings. There is a long tube, which runs between the bearings. Without this tube, the axle would never tighten down properly. Take your chisel and tap the bearing out from the opposite side. Go back and forth from one side of the bearing to the other. Failure to do this can result in a cracked hub. This is not good. Remove the other bearing also. Don't replace just one bearing. Some rear wheels have two bearings on the sprocket side. Replace all these bearings. Some local bearing supply houses may have the same bearing at a fraction of the price of the dealer parts. The old bearing should have some numbers on it. These can be cross-referenced. If no numbers are visible, the dimensions of the bearing can be used to determine the correct replacement. If the option is available, get a double sealed bearing. These can deliver longer life.

Before we install the new bearings, lets make sure they have enough grease. GENTLY pry out the rubber seal with a fine tipped screwdriver. Using a sharp blade can cut the seal. Be careful. Now pack the bearing full of good waterproof grease. We need to tap (pound) the new bearing in place. This will require something that will stand up to a good beating and is almost the same size as the outer diameter of the bearing. The old race will most likely get wedged in the hub. Find one of your good sockets. If you don't have one, borrow your neighbors. He'll think you're using it for loosening a big nut. That's okay just try to conceal the pound marks on it when you give it back. The main thing to be careful of is not damaging the seal and DON'T put any pressure on the inner race of the bearing. This will drastically shorten the life of the bearing. As a general rule with ALL pressed in bearings, don't apply any pressure to the rollers, pins, or balls. Pushing on the inner race exerts all the force on the balls. This applies to your new wheel bearings.

Once you have one side installed, don't forget to put the tube in place. Don't worry too much about getting it perfectly centered yet. It'll move easily enough when the bearing is installed. Once the second bearing is in place, move the tube to the center with your chisel. Hand pressure should move it. Reinstall the retaining devices the manufacture intended and the dust seals.

Ask ten people how to change a tire and you'll get twelve different answers. The method I've had excellent success with is fairly basic but here are a few points which can make the difference between a 5 minute tire change and a 45 minute flesh tearing, wrench throwing nightmare. I have an old gear lube barrel that is about 36" tall with a piece of automotive heater hose split lengthwise wired to the top edge. The tire sits at the perfect height and doesn't slide around. The disc and sprocket are both clear of anything that may damage them. Be sure to break the bead free from the rim on both sides. I have three of the short (8"?) tire irons. I've never needed anything larger than these. If these won't do the trick, more force won't help and can damage a good tire. I use silicone spray lubricant. This works better than most household stuff (like dish soap or baby powder) and is virtually "mess free". Spray both tire beads. I start removing the tire where the rim lock is located. Insert all 3 tire irons before prying the first one. Place them about 5 or 6 inches apart. Now pry the center one first. Once you get the three flipped over, you should be able to use one iron for the rest of the tire. If you're replacing the tube, this is as far as you need to go. Back to tube installation in a minute.

If you're replacing/flipping the tire, I've found it easier to remove the other side exactly the same. In other words, flip the whole thing over and start all over. This will leave you with a rim on the inside of the tire. Just reach in and pull it out. Personally, I've found this much easier than trying to push the tire off one side.

Spray both beads of the new tire with your silicone spray and hook the one side under the rim lock. Then proceed with levering the rest of the lower bead on. Now for the tube. I inflate the tube to the point it will just barely hold its shape if I hang it on my finger. Place the valve stem in the approximate position of the hole and insert the tube into the tire. With the tube 100% installed in the tire, reach in and push the valve stem into its hole. Put the retaining nut on but not all the way down. Halfway down the stem will work for now. Start installing the last bead by beginning at the rim lock. Once I get one tire iron about 90 degrees from the valve stem, I go around the other way until the tire is on completely. Inflate until the beads are in their proper position and set to your preference. Tighten the rim lock.

The valve stem. Two lines of thought here. Most prefer to tighten the stem retaining nut down against the rim. If you do this, you have no warning at all if the tire does rotate on the rim. Rim locks do not work perfectly. Honda CR owners will note their bike did not come with these nuts when the bike was new. They come with a small rubber grommet, which helps seal water and mud out of the rim. I've got these grommets on my Suzuki's valve stems. They retail for around $5 or so each but can be used on any bike you own if you remember to remove them before you sell it. I don't tighten the nut against the rim even if I don't have the grommets available.

That's about it for now. Hopefully, you've learned something helpful.

MX Tuner