Pre-Ride Checklist – 11 Things To Inspect On Your Dirt Bike

A broken dirt bike sitting in my garage is not a happy sight. What’s even worse is when I haul my dirt bike out to the track or trails and it breaks down shortly after my riding session begins. There will always be those kind of days sooner or later, but I have learned how to prevent most mechanical gremlins from occurring just from experience over the years.’

I started taking maintenance seriously when I had an incident that fried a top-end when it probably could have been prevented if I had only checked the coolant level prior to riding. I have now taken the time to figure out a maintenance routine that will keep my bike running better and longer. This list of items to check are the most common things that break or cause a bike failure.

  • Oil/oil filter:

First thing to do is check the oil level and cleanliness. Running out of oil will not only end your day, but also result in a major engine failure. Some dirt bikes have a sight glass on the side of the crankcase to check the oil level, while other bikes require you to check the dipstick. Certain bikes may also require the engine to idle for a minute to circulate the oil before checking it. Always remember to check the oil level with the bike standing straight up in order to get an accurate reading. If you have a four-stroke dirt bike with an oil filter, replace it (or properly clean it if re-usable) every 1-2 oil changes.

  • Air Filter

The next common part to cause problems is the air filter. A dirty air filter can make the bike run rough due to lack of air-flow. A dirty filter will also allow dirt to get past it and into the engine. Having a clean air filter will prolong engine life. Foam only lasts so longer until it starts to degrade and literally fall apart. Strong cleaning chemicals, such as gas, will speed up this process. While filters are meant to be cleaned and reused, do not reuse one if it has any rips, damage, or if you can easily pull chunks out of it.

  • Fresh Gas

A low-performance engine, such as an air-cooled four-stroke, may not be finicky with the gas you run through it. However, old gas will eventually cause problems because it degrades with age and will gum up in the carburetor or throttle body. If you run race gas or mixed gas in a motocross bike, I suggest using it all within a week or two, if not the same day. The longer it sits out, the more it degrades. I have personally had complications using mixed race that was several weeks old; the result was me rebuilding the top-end on my 125cc 2-stroke. If your bike is not running right compared to the last time you rode, there’s a good chance that the gas is either bad, or the carburetor is dirty because it has sat for too long.

  • Spark Plug

There’s three things that an engine needs in order to run; air, fuel, and spark. Once you confirm that it’s getting air and fuel, the next thing to check is the spark plug. First of all, are you getting spark? If yes, then inspect the spark to see if it’s black and/or wet. If yes, then the plug started to or has already fouled. A proper color to see on the tip of a spark plug is tan or light brown. This means that the air-to-fuel ratio is correct. However, gas these days can be pretty lousy with all the additives and give you inaccurate readings. For more information on testing spark, read This Article on Diagnosing a No-Start.

  • Tire Pressure

Have you ever been on a ride and felt the front-end get a really mushy feeling? Sort of like a…. flat tire!? Getting a flat stinks, and it’s even less fun to change it on a dirt bike rim. Always check the air pressure of both tires before riding. The pressure will change with temperature as well, so you may need to add, or even reduce the pressure throughout the day.

Well maintained dirt bikes last a lot longer.
Well maintained dirt bikes last a lot longer.
  • Coolant

If you have an air-cooled engine, you lucked out on this one (the disadvantage is lower performance, but that may not be a necessity anyway). Before starting your bike, pop the radiator cap off and look to see if the coolant level is at or near the top. If you need to tip the bike over far to see it, you may want to figure out why the coolant is low before riding. If it was full on the previous ride and now it’s noticeably lower, it’s probably because the engine started to overheat. It could be a minor problem caused by riding too slow for too long. If you’re continuously losing coolant then you have bigger problems.

  • Chain

A properly adjusted and clean chain will ride smoother and last a lot longer. Signs that the chain needs to be replaced are: kinks, excessive wear or side-to-side play, rust, or stretched beyond the length of the adjusters. You can remove links and continue adjusting it, but there is a much higher risk of snapping a link if it is stretched that far. It’s good insurance to bring a couple spare master links with you in case you do have a mishap. You’ll need a chain-breaker as well.

  • Loose Bolts

This is often overlooked by riders due to lack of experience or just plain ignorance. Some bikes vibrate more than others, and bolts can and will come loose overtime. Loose triple clamp, subframe, or engine mount bolts may break or fall out and cause a catastrophe if you have a hard impact. It may result in broken parts, and quite possibly a bodily injury if it causes a crash. You shouldn’t need to check every single bolt for every riding occasion, but you should make a routine habit of checking all of the critical bolts and torquing them to spec every 5-10 hours of ride time. If you put a lot of hours on a dirt bike, you will start to get the feel for how long things last and when certain parts or bolts need attention.

  • Brake Pads

The faster you ride, the faster you will need to stop in order to turn or dodge an upcoming obstacle, such as a tree. A quick peak at the life of the pads can prevent an accident such as this from happening. If the pad is almost to the end of the wear bar or metal then it’s time to replace them. It’s a fairly simple job on most dirt bikes if you follow the manual. Yes, I know that if you are a guy then you probably don’t want to read instructions, but an OEM manual is a very valuable tool to have if you want to save money by wrenching on your bike(s) at home.

  • Spokes

When is the last time you have checked the tension of the spokes on your set of wheels? If you can’t remember then now is a the time to check. If any of them feel loose, tighten them until they are snug. Spoke wrenches come in many sizes for all of the different sized spokes to make the job easy. Just don’t go too far when wrenching or else the spoke will pop the tube.

  • Controls

Last, but not least, you should test and make sure all of the controls are properly functioning. Is there proper play in the clutch lever (1/8″ to 1/4″ of travel at the end of the lever)? Are the front and rear brake strong; meaning they don’t have a spongy feeling? If they feel like mush or are weak and the brake pads are good then you should bleed them to get any air out that could be in the system. This is assuming that both brakes are hydraulic. If you have drum brakes, check the tension/play in them and adjust if necessary for optimum braking performance.

Any cables that are starting to feel stiff should be lubed. Check for any fraying in the line. If any visible damage, it’s best to replace right away or else it may break when you’re 20 miles into a trail ride. As for hydraulic brake (or clutch) lines, inspect for any rips or tears in the hose. If it’s leaking at the master cylinder or caliper, there’s a good chance that the crush washer or banjo bolt has failed. Do one thing at a time when attempting to fix a part or you will get in over your head in a hurry.

While virtually any part can fail, a regular inspection and servicing of all the items on this list will give you a much better chance of riding all day without a bike problem. Preventative maintenance may not always be fun, but 30-60 minutes of scrutinizing your bike beats losing a whole or even half a day of riding. Just remember that an OEM manual is your friend. Whenever you are wrenching, always check your bike’s specific manual for proper torque and adjustment specs.

Now, GET TO IT, and 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

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

How To Replace A Dirt Bike Clutch – CR125 2-stroke

If you want to ride or race dirt bikes for the rest of you life, there’s some things that you need to learn how to do and fix on them if you want to save time and money. Replacing the clutch should be one of them, and it’s bound to happen if you’re racing or putting a lot of hours on your bike throughout the riding season. Don’t worry, it’s actually a pretty easy job.

If you’re scared to work your motocross bike, I strongly recommend getting an OEM service manual for your bike if you don’t have one already. The factory manual will have pretty much everything you need to know for maintaining or repairing your dirt bike. There’s dozens of diagrams, specs, maintenance intervals, tips on adjusting suspension, and much more.

First thing is to start out with a clean bike and work area. If the bike is not clean, you run a much higher risk of getting dirt or foreign objects inside the clutch/engine, so at least wash that part of your dirt bike. Having a cluttered and filthy shop area is annoying, and can be dangerous if it’s hard to walk. Make enough room to comfortably work on the bike with clean parts and tools.

CR125 Clutch Cover Bolts
CR125 Clutch Cover Bolts

Once you’re all set up and have the proper tools, it’s time to take the clutch off the bike. The clutch cover is on the right side of the engine, and most covers have about 5 bolts holding it on (This bike is an ’01 Honda CR125).

After you get the cover off, you’ll be able to see the basket/plates. There’s five more bolts holding them together. This is where you may need a special tool to hold the clutch to prevent it from spinning while loosening the bolts. If you don’t have one, a cordless impact can be very handy to get it off, although you’ll want something to properly torque it back down.

CR125 Clutch Hub
CR125 Clutch Hub

All of the disks and plates will come out with the pressure plate. This is when you need to check the basket for wear/notching. It will be pretty clear if there’s notches from the disks. This basket does not have notching or appear to be broken, so it can stay right where it’s at!

CR125 Clutch Basket
CR125 Clutch Basket

Next we can measure the springs and plates to see what’s in spec. Refer to your OEM manufacture’s manual for minimum length on the clutch springs and minimum thickness of the metal plates. The min. length of each spring for the CR125 is 35.2mm (1.386″). I measured mine with a dial caliper and it read about 1.430″ (36.2mm), so they’re still within spec.

Measuring Clutch Spring
Measuring Clutch Spring

Next you can measure the metal plates. If they’re still in spec, feel free to use them as long as they don’t show signs of overheating (discoloration). I just bought a complete kit for this bike, so I’m putting in all new plates and disks. Sometimes you can just get away with replacing the fibers/friction plates since they usually wear out faster.

Most clutch plates you will have to soak in oil prior to putting them back on the bike. If you start and run the bike with them dry, you’ll greatly increase your chances of breaking or damaging the clutch. I just take bucket, pour a little engine oil in, and one-by-one place each plate and disk in, swirling the oil around so it covers all of them.

Soak Plates/Disks In Oil
Soak Plates/Disks In Oil

Now you’re ready to put them back in. You’ll start with a friction plate, and alternate until they’re all in. There’s one more friction plate than metal disk, so you’ll start and end with one.

 

CR125 Clutch - Friction Plate
CR125 Clutch – Friction Plate

 

CR125 Clutch - Metal Disk
CR125 Clutch – Metal Disk

After the plates and disks, it’s time to put the pressure plate and springs in. Now you’ll need something to hold the clutch assembly again so you can torque down the bolts. Again, check your service manual for proper torque specs. This CR125 requires 7 ft. lbs. for the pressure plate bolts.

All that’s left is to put the cover back on and fill ‘er back up with oil! Before starting the bike, pull in the clutch a few times and make sure everything feels right, like it’s disengaging and engaging. On the first start, warm the bike up properly by letting it idle for at least a couple minutes. It’s not unusual for the clutch to drag at first; it just needs to be broken in.

Once the bike is warm, ride the bike around for a few minutes to make sure everything is still functioning. After that, you’re good to go! I recommend changing the oil after a few hours of riding if not sooner to get rid of any shavings from the new engine parts.

Click Here To Buy My Clutch Kit!

-Tom Stark