25 Things You Must Look For When Buying A Used Dirt Bike

When buying a used dirt bike, or any vehicle for that matter, you never truly know what you are getting. Just because the seller says it was rebuilt, doesn’t mean it won’t grenade on you an hour after you get home. You don’t know what exactly has been done to it, and they may not have rebuilt it correctly. Not everyone lies about what they have or what’s been worked on, but some people just don’t know. That’s why it’s YOUR job as a buyer to do as much research and scrutinizing of the bike as possible. The more you know about the model of bike you’re looking at, as well as the bike itself, the better you can judge its value.

If you’ve never gone to look at a used bike before, asking a friend to come along that is very experienced with wrenching on bikes is highly recommended because they generally know what to look for. However, you can use this list of things to look for to give yourself a jump-start on bike mechanics 101.

These guidelines relate to motocross bikes, trail bikes, 2-strokes, 4-strokes, air-cooled and liquid-cooled bikes for every make.

  1. “Just look at it” – Upon arrival, you can sometimes tell if a dirt bike is a cherry, or if it is a complete junkbox on wheels. Look at the plastic, frame, and over-all cleanliness of it. If it was put away wet often, there will be a lot of stains and dirt caked on the bottom of the engine/chassis.
  2. Look At Surroundings – This doesn’t pertain to the bike specifically, but while looking at it, take a look around. Where and how is the bike sitting? Is the garage/place clean? How does the seller’s other vehicles look? If everything is clean and looks well taken care of, there’s a good chance the bike was, too. This alone shouldn’t be the determining factor though.
  3. Frame Damage/Straightness – If the dirt bike has been in a major or numerous crashes, the frame or subframe usually shows it. Check for unusual bends/cracks at the welds or where two sections meet. If the subframe is bent, it’s usually easy to see by looking at the bike from the rear. The fender will usually lean more to one side. If it’s too far to bend back, a used subframe is anywhere from 50-200 bucks depending on the bike.
  4. Wheels – Take a close look at both wheels for bends or cracks, as well as missing spokes. If anything is damaged or missing then the bike was ridden hard or rode on rough terrain. Spin the wheels to see if they wobble at all. Used wheels in good shape can be expensive.
  5. Tires – Are the tires worn out or cracked from old age? If they don’t have any sharp edges then you’ll want some fresh rubber for a big increase in traction, which is not only safer, but it will put more power to the ground. A pair of tires can cost close to 200 bucks or more, depending on what kind of performance you’re looking to get.
  6. Suspension – You may need to get it re-valved for your weight, or it may just need to be serviced if the seller hasn’t done it in a while (or ever). This could be as little as new oil and a charge of nitrogen (rear shock).
  7. Bearings – There’s quite a few bearings on a dirt bike, and most of the time you can expect them to be needing new grease at the minimum. Move the wheels side-to-side to check their bearings. If there’s any slop they they need to be replaced. The steering stem has bearings and are usually under-greased from the factory. If it’s hard to turn the handlebars, they may need to be replaced.
  8. Swing-arm/Linkage – With the bike on a center stand, move the swing-arm up and down, as well as side-to-side. It should move freely without binding. If it’s rough or wobbles, it will need to be serviced and may you may need a new bushing kit.
  9. Air Filter – If the seller won’t let you take the seat/panel off to look at the filter, he/she is probably trying to hide something. If you’re looking for a good running and reliable bike, it’s probably best to walk away if they say “No”. If they comply, take a look at how clean the filter itself is, as well as the rest of the airbox. Someone who takes good care of their bike will keep these both clean.
  10. Engine/Transmission Oil – This is just as important as the air filter, if not more so! Most bikes will either have a dipstick or a sight glass so you can easily check the oil level. You should be able to see some oil at least at the minimum level. If you can’t see oil, there’s not enough to properly lubricate. If it hasn’t already, it will cause damage, and is one of the leading causes of blown engines. Many air-cooled trail bikes, such as the Honda XR lineup, is so reliable that some owners never change the oil. Eventually it will run low and will start smoking or seize. However, some dirt bikes require you to start and idle them for a minute in order to check the oil. Make sure you know how to check it before you go.
  11. Chain – Chains can last a long time if they are taken care of. On the flip side, if the chain is never or rarely cleaned and lubed, it can wear out faster than the top-end on a motocross bike. Check for kinks, as well as how far it is on the adjuster. If there’s no room left for adjustment, it’s because the chain is stretched out and is in need of replacement. If the chain has a lot of corrosion or skips at all, it’s toast.
  12. Sprockets – Sprockets usually wear with the chain. You can often get one rear sprocket, and two front sprockets out of the life of a chain if properly maintained. Look at the teeth for any chunks missing or odd shaped teeth from wear.
  13. Brakes – Look at the brake pads for wear. If they’re close to the limit marks or metal, they need to be replaced. Also take notice of the brake fluid in the master cylinder(s). If it’s low or dirty, it may need to be flushed out. Most of this is just maintenance, though, and isn’t too costly.
  14. Coolant – Pop the radiator cap off and check the coolant level. It should be at or near the top. If it’s low then the engine may have overheated and spit some coolant out the overflow tube.
  15. Radiators – After you look at the coolant, take a closer look at the radiators. Are they smashed or bent? How do the fins look? If it looks like it’s been poorly repaired or patched up, you can count on needing a new one, which can be expensive, depending on what you get (new/used/aftermarket).
  16. Handlebars – They can get bent easily if the bike was flipped or wrecked. You can usually tell just by looking at it, but by a simple test ride you should be able to feel if they are bent or not. Aftermarket handlebars often means that the stock ones got bent, along with the possibility of other parts in the process, so pay close attention if so.
  17. Levers – Brake and clutch levers are very easy to bend/break. They are fairly inexpensive, but if more than one needs replacing, the repair bill quickly adds up. The shift lever and rear brake pedal can get bent as well. Make sure the shifter is on tight. If it’s sloppy, the splines are probably worn and it’ll need a new one.
  18. Seat – Does it have any rips? If the cover was replaced, was it put on correctly? This has little to no mechanical function, but some of us like our dirt bikes looking nice.
  19. Fork Seals – Fork seals are cheap and fairly easy to replace with the right tools. However, it can be time consuming, and is quite spendy to have a shop replace them. If they are barely seeping, you might be able to get away with just cleaning them.
  20. Engine Noises – Start and let the engine idle for at least a minute. Listen for any rattling or ticking. If it’s a 4-stroke and it ticks with the RPM of the engine, it’s probably a worn timing chain or tensioner. Fairly simple fix on most bikes. If there’s a rattle that gets noticeably quieter when the engine is fully warmed up, it may be piston rattle, which will require a rebuild.
  21. Transmission – The best way to test the transmission is by riding the bike and shifting through all the gears. It should shift easily up and down through all the gears, with or without the clutch. If you hit a ‘false neutral’ in between gears, it may have a bent shift fork, which requires the cases to be split (a lot of labor).
  22. Clutch – You can test the clutch while you’re riding as well. How big is the ‘friction zone’ or how much movement does the clutch lever have from disengaged to engaged? Or does it even fully engage? A slipping clutch will rev out and the engine may feel really low on power.  You can try dumping the clutch while in gear to see if it slips or engages and stalls. If it stalls or quickly goes to the correct RPM then it probably won’t need to be replaced.
  23. Exhaust – Look at the head pipe for dents or bends. If there’s any major damage, you’ll want to get it repaired or replaced. A crushed pipe will be lacking power. Also listen to the exhaust note. You can usually tell when there is little to no muffler packing because it’s loud and raspy. A freshly packed silencer is relatively quiet (depending on the specific silencer), and will sound nice and crisp. Packing is pretty cheap, but it’s not very fun to replace.
  24. Carburetor – You’re probably not going to be able to internally inspect the carb, but you can get a good idea on how dirty it may be when trying to start it and riding it. If the bike is hard to start and/or has a bog down low, there’s a good chance it will need to be cleaned. This is often the case if the dirt bike has set for a number of months (or even weeks).
  25. Recalls – If you’re going to spend a lot of money on a dirt bike, you might as well get to know your stablemate beforehand. Fortunately, it’s easier than ever these days with the internet. Do some research on the specific make, model, and year of the dirt bike you are looking to buy. Every bike will have common problems after years of use, and while some may cost more to fix than others, you can save money in the long run by planning ahead if you know that your particular bike may need a special part or ‘fix’ in the future.

I know all of this may seem like a lot to take in right away if you’ve never looked at a used dirt bike, but it gets a lot easier the more you do it. Like I mentioned above, it’s a great idea to have a knowledgeable person with you to help. Also, do not be afraid to walk away from a bike. Everyone may say that they have the nicest and fastest bike, but if you want a clean and reliable dirt bike, it’s better to wait than wasting your hard earned cash dollars on a pile of junk that’s going to sit in the corner of the garage after blowing up on your first ride.

Ride safe!

-Tom Stark

5 Signs That Your Dirt Bike Needs A New Top-end – 2 Stroke

If you buy or put a lot of hours on a 2-stroke motocross bike, chances are it will need the top-end replaced. A top-end rebuild is pretty easy to do on a two stroke engine, and the only special tool you’ll need is a torque wrench for most dirt bikes. However, before tearing your engine apart, there’s several signs that can tell you it has a worn top-end. If you have most or all of the symptoms listed below, you can count on replacing at least the piston and ring, and possibly a cylinder and head. Although, if none of the symptoms relate to your bike, there’s a good chance it won’t need a rebuild yet…

It Takes 50 Kicks To Start My Bike…

This is a common symptom for both two and four stroke dirt bikes. Unless you are riding in extreme climate, your bike shouldn’t take more than a few kicks to get started. Certain bikes require more muscle and/or technique to get started, but a solid running engine will only take 1-3 kicks to start, hot or cold. On the flip side, just because your bike takes forever to start doesn’t always indicate a worn top-end. For more info on a ‘no-start’, read this article on Diagnosing A No-Start

My Bike Is Gutless

Does your dirt bike feel like it lost its power-band(sarcasm)? A worn piston/ring will make the engine feel weak and low on power even when WOT (wide open throttle). This often happens after a top-end has so many hours on it, and will get worse/less powerful over time. A 2-stroke piston can last over a hundred hours if the bike was casually ridden and properly maintained, but an aggressive motocross racer can wear out a top-end in less than 20 hours of ride time.

This Thing Eats Spark Plugs

Shattered CR80 Piston
Shattered CR80 Piston

How often are you replacing the spark plug? If you have to put a new one in every ride, stop and inspect before riding again. If the jetting is right, a fouled spark plug can also be caused by a bad top-end or blow-by from the worn piston/ring/cylinder. This definitely indicates a new top-end is required, as well as a new spark plug. I have personally seen a CR80 that fouled plugs because of a bad top-end. It turned out that the piston was cracked and it eventually just lost compression. The cylinder was used again because it was surprisingly still in good shape! Here’s some more causes of a fouled plug.

Look For Scratches

A scored piston or cylinder can be caused by multiple things. A lack of lubrication from not enough 2-stroke oil in the gas or lean jetting can damage the piston and cylinder, as well as the crank assembly and bearings. Scoring is caused by metal to metal contact, which is common on 2-strokes when they aren’t warmed up properly. It makes me cringe when people try to warm up their dirt bike too quickly, and I see it quite often. A lot of top-end damage is done if you start your bike and immediately ride it hard or rev it without giving it enough time to warm up.

A piston has a certain amount of clearance between it and the cylinder wall. This clearance is for “growth”, because it will get bigger as it heats up. The size difference isn’t much, but if the piston heats up too quickly, it will expand faster and get too big to properly fit in the cylinder bore, thus creating scoring, and possibly a “cold seizure”. Read the article in the link above to learn how to warm up your dirt bike without damaging anything. You should also note that forged pistons, as opposed to stock cast pistons, are slightly smaller in diameter and require more warm-up time to expand; so take extra precaution.

You may have to take the cylinder head off to get a good look at the cylinder walls to check for scoring, but there’s a quick and dirty way to give you an idea of its condition without touching the engine itself. Just unbolt and remove the pipe/expansion chamber so you can look in the exhaust port of the engine. Shine a light in there and see if there’s any noticeable scratches. You can look at the piston as well, but any scratches/scoring that looks like something you can feel with your finger nail is damage and will most likely need repair/replacement. If you can’t see the cross-hatching on the cylinder walls then it is worn and probably out of spec.

Top-end Rebuild
Top-end Rebuild

My Bike Is Super Easy To Kick Over

If you don’t know already, this isn’t a good thing. While most 2-strokes are easier to kick over than a four-stroke dirt bike, you shouldn’t be able to push the kick-start lever down with one finger. If it kicks over with next to no resistance, the top-end is probably down on compression. Low compression will usually go hand-in-hand with taking a lot of kicks to start, as well as a weak engine.

A new piston ring may be the only thing that needs replacing if the piston and cylinder are still in good shape. Rings only last so long and eventually go out of spec (refer to your manual). If you have the cylinder off, check the ring gap with gauges and compare to what the manual says. If the gap is too big, replace the ring with a new one. You can usually re-ring a piston once before needing a new piston as long as everything else checks out.

These tips are only guidelines. Nothing is set in stone, as every bike is different. Just because your bike is hard to start doesn’t mean it will always need a new top-end. It could be something completely different, such as a dirty carburetor because the bike hasn’t been started for months. I put this list together because these are the most common symptoms of a bad top-end when all of the simple problems have already been checked.

Have fun, and ride safe!

-Tom Stark

How To Convert A Dirt Bike To A Street Legal Supermoto

Motocross Hideout includes anything dirt bike related, even if it is ridden on asphalt. So, just what is a Supermotard? Yep, a dirt bike with sport-bike style wheels and tires for riding on the street. If you’ve ever ridden a dirt bike on the street, you’ll know how exhilarating it can be when you whack the throttle and the front wheel comes off the ground. Motards are the ultimate hooligan bike, and can get you into a lot of trouble if you don’t follow the rules. However, if you want to legally ride on the street or go to track-days on a road course with your dirt bike, here’s some things you will need to replace or install.

Wheels

If you want to convert your dirt bike to a supermoto, you’re going to need ‘Sumo’ wheels and street tires. 17 inch wheels, front and rear, are the most common for supermoto, and are much better for street riding than the stock 21/19 that are stock on most full-size dirt bikes. They lower the bike, they handle better, and they’re wider so you can lay more rubber down. 3.5″ width is typical for front supermoto wheels, and 4-5″ are the most common for the rear, with several in between. You can go wider or narrower, but you may run into tire width issues, as well as the wheel being too wide and rubbing on the chain and/or swing-arm.

Tire size selection is important in order to make your motard ride right. If you have a rear tire that’s too wide, it can actually hinder the performance. For example, if you have a 4.25″ rear wheel with a 160/17″ tire, the wheel will be pinching the bead of the tire because it is wider, thus creating a more extreme profile with a smaller radius, and ultimately less road surface. However, if you put a 150/17″ tire on the same wheel, it will have more contact surface on the road and perform better than the wider tire. This is research that you should do for your specific year and model bike to determine what combination is best.

Supermoto Wheels
Supermoto Wheels

 

There is also the more extreme route for those that have the machining ability and want to possibly save a few bucks. Street bike wheels from certain bikes can be retrofitted to work with your dirt bike. However, there is usually machining involved to make clearance to fit on the swing-arm and/or forks. Bearings are fairly easy to swap out, but you’ll either have to find wheels with the same size bearings as your dirt bike to fit the axle, otherwise you have to buy some bearings with the correct size inside and outside diameters. Another problem that may come up if you choose to do this conversion is mounting the caliper. This depends on what size rotor you’re going to use, or if you want to put the stock caliper on the wheels you’re using. I can’t recommend a certain set-up for everyone, as there are so many different bikes and combination of wheels. Unfortunately, that is where YOU will have to read-up on as well. I don’t recommend going this route unless you are mechanically inclined and have the machining capabilities/resources. Lastly, cast wheels are not as strong as spoked supermoto wheels, and they will not be able to withstand the abuse of jumping and off-road riding; just something to keep in mind as well.

Lights

Lights are required if you’re going to ride on the street. Every state is different, but the usual requirements are a headlight (hi/low beam), tail-light/brake-light, mirror, turn signals (hand signals are OK in some states), and reflectors. Headlights are fairly easy to install if you carefully read and follow the instructions (I know, that can be hard for the guys…). However, if you are using a motocross bike, you will either need an alternate or bigger power supply. An upgraded or rewound stator is probably the easiest way to go because that alone will power the lights. You’ll need to get a regulator to go with it so you don’t burn the lights out.

Lighting Kit
Lighting Kit

Unfortunately there’s not an aftermarket stator for every dirt bike, or at least one that’s reliable. Another easy way to get usable lights for your street legal conversion is with battery power. You can buy an aftermarket lighting system for most bikes, such as the DRC EZ electric wire kit. It is powered by a battery pack of 8 AA batteries that are easy to swap out. They will last several hours, depending on how many lights you have and what kind of wattage they pull.

Another option would be using rechargeable Lipo batteries, such as ones used in RC planes and cars. They should be 12 volt (4 cell) to match the lighting system. This route requires a little more initial cost, but being able to recharge the battery makes it easy, especially since you don’t have to worry about carrying around a bunch of small AA batteries.

Brakes

In order to go faster, you must be able to stop faster. If you’re converting your dirt bike to ride on the street or asphalt, you will want to upgrade the front brake. The rear brake isn’t as important because it’s not doing as much braking, so it’s adequate for most riders unless you’re highly competitive in supermoto racing. The brake-system is fairly simple in regards to modifications. You have the master cylinder, brake line, caliper, and rotor. The quickest way to get more braking power is by replacing the rotor with a bigger one because it produces more leverage. 320mm is a popular rotor size for motards to have, but there’s some things you’ll have to consider.

Most bikes can use the stock caliper with a larger rotor, but the stock location will not work. This is why you must buy a relocation bracket in addition to the rotor. Be sure you buy the correct bracket, though, as the size/brand of rotor and caliper may vary. Calipers with four or six pistons are a common upgrade, as this will also produce more stopping power.

A steel or aluminum braided brake line is a fairly inexpensive accessory to your braking system, and they perform better than the stock rubber hose. They are built to withstand more pressure, and give you a more consistent and less “mushy” feel compared to stock.

Upgrading the master cylinder can get expensive, but if you are racing and want the most power with less effort, a better Master will complete the package. There’s quite a few options out there to choose from, and generally, you get what you pay for. On the flip side, many riders on a budget find an MC from a different dirt bike, street bike, or even a quad that is better than what they already have. Remember to do some research as to what works with your specific bike if you decide to upgrade.

Sumo Front Brakes
Sumo Front Brakes

Accessories

Last, but not least, are the ‘accessories’ that you must add to your motard to make it “street legal” and pass inspection if needed. Every state is a little bit different, so I will just hit the basics on what’s required. Almost, if not every, state will require a working horn. This doesn’t have to be anything fancy. In fact, a lot of riders buy a cheap bike horn from wal-mart. Turn signals may or may not be required. Hand signals are legal in some states.

Most states need a headlight with a hi-low beam headlight, as well as a working tail/brake-light that works with the rear brake. Reflectors are a good idea, whether they’re required or not. It will make you a little easier to see, and if you get pulled over, the deputy may take you more seriously if you add little safety things like this. You will likely need a mirror to be legal, so a simple handlebar mounted or bar-end mirror will work.

A road-legal exhaust is a good idea if your bike is being inspected. Most dirt bikes have “For off-road use only” stamped on the stock exhaust, which isn’t going to fly if a cop scrutinizes your motard. Also, bikes that carry passengers must have an appropriate seat set-up and passenger pegs. I know that supermoto’s are solo-bikes 99.9% of the time, but it’s just something else to keep in mind.

Now it’s time to start building your bike! All of these parts add up quickly, which is why properly set-up supermotards (especially when plated) are so expensive to buy used. You probably won’t get your money back when you go to sell it, but it can be worth the money to know that you built it with all of the parts that you want. If you do some shopping around and have the whole winter to piece your bike together, you can find some good deals on used or even new parts. Besides, if you buy a complete supermoto kit for your dirt bike, you can always go back to the stock set-up if you want to ride in the dirt again.

I know that was a lot to take in, so you should bookmark this page/website and come back to it throughout your build. If you just want to see all the parts involved in making a supermoto, here’s a simple list (how far you want to go down it is your decision):

  • Supermoto wheels and street tires
  • Street gearing/sprockets (depends on what kind of riding you’re doing)
  • Headlight
  • Tail/brake-light
  • Upgraded stator or battery system for lights
  • Larger front brake rotor and relocation bracket
  • Better front brake caliper and master cylinder
  • Turn signals
  • Mirror
  • Horn
  • Hi/low beam headlight switch
  • Reflectors
  • Street legal exhaust
  • Passenger seat/pegs

If you have any questions, either post a comment below or click the Contact tab above and shoot me an email. Have fun building your own Supermotard, and ride safe!

-Tom Stark

My Dirt Bike Won’t Run – Diagnosing A No-Start

Any day your dirt bike won’t start is a bad day. The problem could be as simple as turning on the gas. However, if regular maintenance hasn’t been performed, you could have a much bigger underlying issue. Not changing the oil in 20 some hours can do a good deal of damage to the engine. If you just haven’t ridden the bike for a few months and it’s just been sitting in the garage since you last rode it, you can often find and solve the problem in less than an hour.

In order an engine to run, it needs air, fuel, and spark. If your dirt bike is not getting just one of these, you can kick it over all day long and it won’t start. In order to save some possible time, we’ll take a quick look at each of these areas to see if we can spot something simple. That way we won’t spend an hour trying to fix one thing when the problem could be something completely different.

Oxygen

Air comes first, so pop the side cover and/or seat off and take a look at the air filter. This may be a dumb question, but is there a complete air filter there? It’s easy to stuff a rag in there while working on the bike and forget about it when you go to put everything back together. All I can say is, stranger things have happened, and it’s always safe to check first, especially since it only takes a minute. If the air filter is there, how dirty is it? If it’s caked with sand and mud, that alone could be preventing your no-start problem. Clean the filter and try starting it again.

A less-common, yet possible cause, could be an air-leak in the system. Check the intake boot for cracks, as well as any bolts or gaskets in between the airbox, carburetor, and engine. On a 2-stroke engine, the reed valve has pedals that wear out over time. They can last hundreds of hours if the bike isn’t ridden hard, but if the edges are chipped off, it could let unwanted air through and not allow the bike to start. This takes longer to remove and inspect, but it’s just one of the many things that can cause a no-start dilemma.

This filter looks a little dirty...
This filter looks a little dirty…

Fuel

The engine requires air and fuel in order for combustion to occur, so the next step is make sure the engine is getting gas/premix. First place to check is the gas tank. Is the tank clean with fresh gas? Gas or premix that has sat for a number of weeks will degrade and start to gum up. If the gas smells like old paint, dump it out before doing anything and clean the tank out. Fuel must go through the petcock to get to the carburetor, so if the tank is empty, now is a good time to take a peek at the seal and filter on it. If they are damaged, leak, or clogged, replace with new parts/assembly. If the gas line is cracked or plugged, replace it as well.

Next up is the carburetor, which is the root cause of many ‘no-start’ situations. Especially on smaller dirt bikes with smaller carbs, jets and passages can gum up in a matter of weeks because of old gas sitting in it. Even if you can see through the pilot jet, there may be just enough crud stuck on it to not allow a sufficient amount of gas through to ignite the engine. Carb cleaner and compressed air are your friends if the carburetor isn’t too filthy. You can often times just loosen up the carb clamps and rotate it to spray out the jets while still on the bike. This can be done in a matter of minutes by removing the float bowl on the bottom of the carburetor.

If that doesn’t work, you may need to take the carburetor completely off and dis-assemble it for a more thorough cleaning. There’s a couple more quick ways to confirm that the carb may be dirty. You can pour a little bit gas in the spark plug hole and kick it over. If it starts or fires for a second or two then you know it’s not getting gas from the dirty carb. You can also try and push start your dirt bike. If neither of those work, it may not be a fuel problem after all, but lets move on to one more quick check before taking the time to clean the carburetor again.

Spark

My dirt bike may be getting air and fuel, but if there’s no spark, it won’t even want to start. A quick way to check if it has spark is by pulling the spark plug off, putting the cap back on, and resting it on the engine while slowly kicking the engine over. You may need to turn off the garage lights to see it, as it will be a small, blueish spark of electricity on the end of the spark plug. If you don’t see anything, be prepared to do spend a good amount of time swapping out parts if you don’t want to replace everything in the electrical system.

If you know someone with the same bike, ask if you could temporarily rob some electrical parts off of theirs. It could be as simple as a faulty kill switch, or a bad ground in the system. However, you may have to swap out the CDI box or even the stator to find the root problem. Once you find the part causing the problem, order a new one and give your generous friend back his/her parts, as well as taking them out to lunch if they lent you a hand in your project because they could have saved you a lot of money by not ordering the wrong parts.

If you still can’t figure out why your dirt bike won’t start, there’s a good chance that it needs a rebuild if it has a lot of hours on it. Low compression is common on motocross bikes that have been ridden for years. If you check the engine compression when the engine is new, you will be able to tell when it needs to be rebuilt when the compression goes more than 25% below what it started at.

If you have any questions, post a comment below… Have fun, ride safe, and keep those dirt scooters maintained!

-Tom Stark

How To Remove and Replace Wheel Bearings On A Dirt Bike

Wheel bearings inevitably fail over time, and that time is much less if you often ride your dirt bike through water. Water and mud will eventually seep inside if you leave it wet, causing the bearings to rust and end up seizing. An easy way to tell if your dirt bike wheel bearings are shot is by moving the wheels side to side. If the wheel moves at all then the bearings need to be replaced. Some tools you will need to replace wheel bearings include:

  • Wrenches to remove wheel
  • Screwdriver
  • Punch
  • Bearing retainer tool/pliers
  • Hammer
  • Bearing installer/socket

Before taking any parts off your bike, give it a bath so that it’s easier to work on. Keeping your dirt bike clean makes working on it much easier, keeps you cleaner, and you will be able to tell much sooner if there’s a leak or other problem with your bike. Once your bike is spotless, set it on a stand and remove the wheel that you are replacing the wheel bearings on. Now put the wheel on a wheel stand, a wooden box, or even saw horses to make it easier to work on without damaging the rotor or sprocket.

Wheel Bearing Retainer Removing Tool
Wheel Bearing Retainer Removing Tool

Remove the seals by prying them off with a screwdriver so you can get at the bearings. One side will have a retainer clip or nut, such as the one on Honda motocross bikes, which you’ll want to buy the special tool for. They are pretty cheap for a specialty tool, but make sure you get the right size because they changed over the years. You can try tapping it out with a small punch if you’re careful, but I wanted to re-use the retainer, and for under 20 bucks, it’ll pay for itself even if I only use it a couple times. Tools like this will save you time and the hassle, especially if you need it again sometime down the road.

Once you remove the retainer, flip the wheel over to remove that bearing (If you bought a fancy bearing remover tool, just use that, otherwise for the rest of us that are cheap, continue reading these instructions). Before you go to punch it out from the other side, you’ll have to take the punch and push the wheel spacer that is in between the bearings over so you can hit the bearing with the punch. Now just hammer on the punch to knock the bearing out of the wheel. Punch the bearing in a circular rotation so that the bearing comes out straight and doesn’t gouge the bore of the wheel. The wheel spacer will come out once that first wheel bearing is out, so set that aside until you need to re-install it.

Now you can flip it back over and knock out the other bearing(s). Just make sure you punch them out as straight as possible. Before you install the new bearings, I recommend putting them in the freezer. Metal slightly shrinks at cooler temps, so this will help make the installation a little easier. Clean the area and surfaces of the wheel on both sides where the bearings go in and set your wheel back on the stand/wood blocks.

Some people say to heat up the hub where the bearings go to make it easier to install them, although others will say that it weakens the metal. I haven’t seen any issues caused by heating it, but it’s up to you whether you want to use heat or not. I didn’t use any on my recent rear wheel from a CR125, but it took a little more force to press the bearings in.

Take the wheel bearing and set it on the journal where you will press it in. You can start out with a piece of wood or flat piece of metal and hammer it in until its flush. Make sure you know that it is going down straight, otherwise it can damage the surface. Next, you’ll have to use a round piece of metal or a socket that is almost the same size as the bearing. You want to be hitting on the outer race (outside circumference) of the bearing and NOT the inner race. If you press or hammer on the inner race you will destroy the bearing. Keep hitting the bearing down while making sure it’s straight. You will hear or feel when it bottoms out in the bore, and that’s when you stop. Now you can put the clip or retainer ring/nut back on, along with the seal.

Removing Seal and Bearing
Removing The Seal and Bearing

Flip the wheel over to do the other side, but before you put the other bearing(s) in, REMEMBER TO INSTALL THE WHEEL SPACER. This is just the sleeve that you took out that goes in between the bearings, and it can be easy to forget until after you press all of the bearings in, resulting in hair-pulling frustration. Now you just repeat installation on this side, whether you have one or two bearings left. If you’re doing it all by hand, just be patient and get them in straight. It may take some time, but the bearings will go in (assuming you bought the correct part).

Now you can install the other seal to complete the wheel bearing installation. When you go to put the wheel spacers on, put some waterproof grease on them to help protect the seals and bearings. If they are worn with grooves then they should be replaced, otherwise water will find it’s way to the bearings much easier.

That’s it, just put your wheel back on the same way you removed it and remember to properly torque the bolts. If you have any questions, don’t hesitate to post a comment below…

Good luck, and ride safe!

-Tom Stark