Over the years 4-stroke dirt bikes have improved thanks to technological advancements. There have been power increases, weight decreases, and the performance of 4-stroke engines have become a lot more efficient. Nonetheless, these types of bikes require maintenance, and while maintaining a 4-stroke isn’t as intensive as a 2-stroke, you’ll still want to make sure you know what needs to be done.
4-stroke Dirt Bike Maintenance:
- Wash, Dry Inspect, Tighten and lube bike (Every ride)
- Oil change (4-6 hrs)
- Replace Oil Filter (6-10 hrs)
- Clean, Check, Replace, and Oil the Air Filter (Every ride or 3Hrs)
- Replace Brake Fluid ( 20-40 hrs)
- Replace Pads (0.04 in-1.00mm)
- Check Calipers and Rotors (Regularly)
- Check Coolants (Every ride, change yearly)
- Check Tire Pressure, Valve stems (Every ride)
- Check Tire and wheel Condition (10k, lube every 6 months)
- Check for Engine, Brakes, etc… for leaks (Every ride)
- Check Chain tension and Sprockets (Every ride)
- Check Control Cables (Regularly)
- Change the Piston and Rings (Every 30-100 hours)
- Check Suspension/Steering (Regularly)
Make note that the maintenance of a 4-stroke dirt bike is different from that of a 2-stroke as the engines are different.
Read on to learn more about the difference between 2-stroke and 4-stroke, the importance of creating a maintenance schedule, and tips on maintaining a 4-stroke dirt bike.
How Does a 4-Stroke Engine Dirt Bike Work?
A 4-stroke engine consists of four functions, which include exhaust, combustion, compression, and intake. This type of engine is more complex than that of a 2-stroke engine. That’s because a 4-stroke engine power is fired every two revolutions of the crankshaft, something that allows for steady power delivery.
Also, the 4-stroke engines feature a smooth powerband that makes handling easier. It’s the reason why dirt bikes with this type of engine are preferred for beginners. They require little effort to ride. The 4-stroke dirt bikes have more moving parts, and there’s controlled engine power, which means you don’t need to worry about shifting, clutching, or the brakes.
Another reason why 4-stroke dirt bikes are preferred is that they require less maintenance than 2-stroke bikes. You can comfortably use these bikes for trail riding. Nonetheless, having too many moving parts also means the bike becomes heavier than that of a 2-stroke engine. You may also need to account for the replacement of the moving parts.
4-stroke dirt bikes have more power down low. Users of the 4-stroke dirt bikes prefer them because they are easy to maneuver, control, and ride.
Differences Between 2-Stroke and 4-Stroke Dirt Bikes
Some of the major differences between the two include:
Modern 4-Stroke dirt bikes have an excellent power performance due to the different advanced versions of the engines. 2-stroke dirt bikes, on the other hand, have a high power performance, but this can be difficult to control when trail riding or controlling the bike on rough terrain. The best part is that a 4-stroke bike has better power handling as power management is better than that of a 2-stroke.
Another difference between the 2-stroke and 4-stroke engine is the handling. Four-stroke engines are heavy as they have multiple moving parts. The result is challenging handling. However, two-stroke engines have fewer parts, something that makes them lighter and easier to handle. The good thing is that adding suspension can reduce handling problems in a 4-stroke dirt bike.
Another difference between the 2-stroke and 4-stroke is in the operation. A two-stroke engine has oil mixed with fuel inside. The combination goes through a combustion cycle where it burns up and leaves through the exhaust pipe. There are some 2-stroke engines with an oil injection system that adds oil into the carburetor.
2-stroke engine oil is refined as it needs to mix well with the fuel and burn in the combustion chamber. These oils are thinner and have specific additives. You can find 2-stroke engine oils made from synthetic, conventional, or castor oil.
The 4-stroke engine has a separate chamber for the fuel. There is a pump that circulates the fuel through the engine, while the filter removes unwanted particles. The process repeats, and although the oil can be recycled, it’s best to change it after some time to avoid contaminant buildup.
Four-stroke engine oil isn’t as refined due to the circulation system. Nonetheless, additives may be added. Viscosity plays a critical role in how the engines function.
2-stroke engines have less moving parts, hence less repair and costs to rebuild. A 4-stroke engine consists of multiple moving components, which means you may have different parts to repair. That makes it costly to rebuild this type of engine.
Another difference between the two engines is in the maintenance. Like repair, maintaining a 2-stroke is easier because of the few moving parts. A 4-stroke bike will need more maintenance as there are a lot of parts involved.
The Pros and Cons of 4-Stroke Dirt Bikes
- They are fuel-efficient
- Only gasoline required to fill up
- Durable with proper maintenance
- More maintenance is required
- Predictable power delivery
- Can be extremely loud
- Heavier due to the many moving parts
Change the Oil Regularly
A 4-stroke dirt bike has so many moving parts, which is why you need to change the oil regularly and lubricate these parts to ensure longevity and guarantee performance. Failure to change the oil means you may be unable to race or ride because your bike needs an engine rebuild.
How often should you change the engine oil for your 4-stroke dirt bike? The recommended time frame is five to ten hours. However, this depends on the times you race. It’s also best to buy stainless steel reusable filters as they only require cleaning using a contact cleaner when changing the oil.
When cleaning the oil filter:
- Spray every part with a contact cleaner to remove all the debris.
- Focus on the edges and the corners where dirt hides.
- Allow the filter to dry before putting it back inside.
You should start by reading the owner’s manual for the process of changing oil and get your model of bike. Modern 4-stroke bikes have a single oil compartment, while others have two-one for engine oil and the other for transmission. Checking the oil filler caps will tell you how many compartments your bike has.
If you are forgetful, simply write down the time you last changed the oil and remember to clean the air filters each time. That will ensure you never have to deal with engine failure.
What’s more, when dealing with a 4-stroke dirt bike, you need to change the oil filter. If you are using the stainless steel filter, you only need to clean it every time you change the oil. However, when using the disposable filter, you need to change it each time you do the oil.
What Happens to a 4-Stroke Dirt Bike Engine Without Oil?
Engine oil is what lubricates the metal parts in the engine. Lack of proper lubrication means that these parts will rub against each other at high temperatures. The result is premature wear and, finally, a damaged engine. You may need to replace most of the engine metal components, which is expensive.
How to Change Oil in a 4-Stroke Dirt Bike
Here are the steps to follow:
- Take the bike for a ride until the engine oil is warm. Doing this helps the used oil drain better.
- Put an oil pan under the bike’s bottom and remove the oil filter cap on the bike’s side. Unscrew the drain bolt on the bottom of the dirt bike. You’ll start seeing oil pouring out. At this point, shake the bike from side to side to ensure you get everything out.
- Remove the oil filter cover. Take the filter out and place a new filter, ensuring you cover it with some oil for a good seal.
- Use a contact cleaner to remove any particles and hunk on the filter cap that could block oil flow. Fit the cover in place, but avoid over-tightening the bolts. Check the rubber o-rings to see if they are loose or worn out. You’ll need to replace them if they are old and don’t fit properly.
- Tighten the drain bolt and add fresh oil. Use a funnel to avoid creating a mess and ensure you put the recommended amount from your user manual. Some bikes have this written on the engine casing.
- Clean the oil filler cap and put it tightly.
Tips on the Type of Oil to Use in a 4-Stroke Dirt Bike
The kind of oil you put depends on the bike’s brand and model. All this information is available on the user manual, but here are some tips that you should consider:
- Don’t go for the cheapest oil in the market. Instead, opt for high-performance oil. Although it may be costly, it will keep your engine running smoothly.
- The type of oil to choose also depends on API classification and viscosity. The thickness of the engine level is the viscosity.
- Some engine oils are best for cold weather, while others work for warm weather.
- Another factor to consider is the API classification.
- Find an oil with a classification of SG or higher, apart from oils labeled as resource-conserving or energy-conserving on the label.
- Most dirt bikes will use engine oils rated equally in performance to SJ.
- You should stick to the name-brand dirt bike oil if you are unsure of what engine oil to get.
Be Careful About the Coolant
4-stroke dirt bikes are more involved as they have multiple moving parts. These parts can overheat and affect you on the track. Unfortunately, you can’t just add coolant and forget about it.
The 4-stroke coolant is designed to lower the engine temperature drastically and keep the engine parts from breaking down and overheating. You need to change the coolant regularly if you ride a lot or go to the sand dunes.
Check the Tire Pressure
Another essential aspect of a 4-stroke dirt bike maintenance is tire pressure. You need to check the tire pressure in between each ride. Begin by checking the tread and any signs of visual damage like flat spots or cracks. Inspect the tires for any stuck objects in the tire like glass pieces or nails that could damage your tires.
Most riders get a range of 10,000 miles with a pair of tires. Nonetheless, this is dependent on how you ride the dirt bike and the type of bike you have. The front tires last longer than the rear ones.
It’s also critical to check the tire pressure of your dirt bike tires, especially if you are taking long rides. That helps to prevent wear and tear.
- The best way to check tire pressure is to use a tire pressure gauge. There is an electric pressure gauge that checks the tire pressure in a minute or less. Experts recommend checking the pressure on cold tires before you ride and not after.
- Check the pressure of the tires often when they are new. Afterward, you can extend the pressure check intervals.
- The recommended dirt bike tire air pressure is between 10-21 psi. You’ll need to read your user manual to know the pressure your bike needs. You can adjust tire pressure down or up to get the right traction on the terrain you’ll be racing or riding on.
- Tires that are soft feel spongy and roll on the rim, while tires that are too hard means less grip.
All of these could affect your performance. Incorrect tire pressure could lead to uneven tire wear, tube/tire failure, punctures, and sometimes the tire may come off the bead.
Check the Valve Stem
After checking the tire pressure, you need to check the valve stem:
- Air leaks often happen in the valve system as opposed to tire punctures or holes in the tube.
- The valve can have dirt and debris that creates gaps in the seal.
- When checking the valve stem, ensure the caps are on and tightened.
- If your stem has spun, you need to deflate the tire and reset it.
Check Tire Tread, Spokes, and Rim Locks
The next step is to check the tire tread. Most traction is from the knobs that get into the terrain, instead of friction between the pavement and rubber when riding, Check between the knobs for cuts and cracks in the tire as this could affect traction.
The tire spokes and rim locks are an essential part of the tires. They need to be tight in place and straight. Find out if the rim locks are fastened.
Sometimes you may need to replace the tires. A few signs you may need to replace tires include: cracked tires, rounded knobs. discolored tires, missing or torn knobs, and tires that are more than a year old.
If it’s time to replace a tire, it’s recommended to replace both tires even if one looks better than the other. Overall, tire pressure is about experimenting. Begin with 12 psi and go down or up with the tips.
Check for Leaks
When your engine is clean, you can quickly spot oil and air leaks. You’ll notice oily drips or marks on the floor. Other signs include sooty marks on the exhaust and cylinder. Check for leaks on the brake calipers, brake fluid reservoirs, and hydraulic brake cables.
Other areas prone to leaks are coolant pipes, radiators, and the water pump gasket. In case of any leaks, ensure that you deal with them before riding the bike.
Inspect the Sprockets for Wear and Damage
The chain and sprocket are critical in any dirt bike. Unfortunately, dirt wears out the bushings and rollers. Although lubricating the chain might seem like a good idea, sometimes it could worsen the situation. The lube forms a sticky substance that attracts dirt. You need to clean the chain as this makes inspection for damage easier.
For sprockets, look for any eroded/chipped teeth and missing teeth. Worn sprockets are easy to spot. Other indicators include bent rear chain guides, bent sprockets, or chain rub blocks that are worn through. If you find them damaged, it’s best to replace both the chain and sprockets.
Another area where people make a mistake is in the chain and sprocket alignment. That’s what leads to premature chain failure. Make sure that the chain is centered on the sprocket tooth. Use a chain adjuster to correct the misalignment.
Ever wondered how long the chains and sprockets last? All that depends on the riding environment, maintenance, and rising habits. If you want the sprockets and chains to last longer, make sure that you inspect the drive components regularly, adjust the chain properly, and keep the drivetrain clean and lubricated.
Check the Brakes and Brake Pads
Brake pads tend to wear out over time as the material breaks down until all that is left is the backing plate. The hardened steel can damage the brake rotor when this happens. Moreover, you could end up with brakes that no longer work. It’s critical to check your motorcycle brake pads routinely.
Brake pads that are between 0.04 in and 1.00mm need to be replaced. Some brake pads have indicator marks that are no longer visible when worn out. That is an indication to replace them immediately. Also, you need to replace other brake components like the rotors.
Carry Out Air Filter Maintenance
Your dirt bike’s air filter helps get rid of external elements you may encounter while riding. It’s essential to check the air filter regularly as dirt and debris may be embedded in the filter and not visible to the eye. Accumulation of moisture in the air filter can also result in other consequences.
Experts recommend atleast cleaning the air filter after one ride. Ensure that the filter is also covered in a good amount of oil, as too little can easily get through the intake, and too much can weep into the engine. The air filter should be replaced between 6-10 hrs of riding depending on how hard you ride and terrain.
Exhaust Pipe Maintenance
Focus on cleaning the outside of the exhaust pipe to prevent corrosion and rust. Don’t forget to check the muffler packing. Four-stroke bikes have the muffler packing compressed, which makes it ineffective. If you notice the compression, it means that it’s time to replace it.
The best exhaust packing prevents the exhaust from becoming too hot. Some are made from fiberglass for durability and maximum performance.
Your dirt bike is designed with mudguards, fenders, and side paneling to protect you and your bike from debris and dirt. They also come in handyman the event of a crash. Regular cleaning can prevent plastic parts from looking old and faded.
When restoring the plastic parts, some experts suggest sanding the plastic as it allows for better absorption. There are plastic restorers that provide a clean and fresh look by working as an undercoat protector and a lubricant. Some block UV rays to reduce cracking and fading.
Carburetor Care and Maintenance
Carburetors in a 4-stroke dirt bike regulate airflow through the main bore. It’s this flowing air that draws in fuel, and the mixture gets into the engine through the intake valve. They consist of a center bore, a bowl, passage, vents, jets, a slide, air/fuel ratio adjustment, accelerator pump, and idle speed adjustment.
Some of the signs that show you need a carburetor tuning include:
- A bike that isn’t smooth to accelerate
- Engine hiccups when the throttle is opened
- The engine overheats even when you don’t race a lot
- Reduced fuel efficiency
The importance of carrying out routine maintenance is to determine the right air-to-fuel ratio that the engine is getting. Adjusting these ratios ensures that your bike functions optimally. If you have a weak spark, check the ignition coil. A damaged ignition coil causes the engine to miss at high rpm and run erratically.
Clogged carburetor vent hoses are another problem that needs to be addressed. Any dirt and debris accumulation in the hoses or vent tubes causes jetting to be lean, something that makes the engine sluggish.
A worn carburetor fuel inlet needle needs to be replaced every two years. Failure to replace it means the fuel will get into the float bowl and go up the pilot jet and into the engine.
Spoke Tightening and Maintenance
Spoked wheels are more durable than single-piece cast wheels, and that’s the reason they are fitted on most dirt bikes. However, the spokes which are between the tire and rim are neglected. Loose spokes cab damage or break the rim, which is something that can be costly to repair or replace. Also, overtightening strips the thread and stresses the rim.
You need to check the spokes regularly by tapping them with a metallic item. A dull sound will be heard if you have loose spokes, while tight spokes have a high pitch. Check if your wheel is running true by placing it on a stand and allow it to spin freely.
Maintaining dirt bike spokes requires tightening them when they become loose. Follow these simple tips if you’re doing this on your own:
- You can use a spoke wrench or get a spoke torque wrench to tighten the spokes.
- Avoid using pliers as it could damage the nipples.
- Put the spoke wrench over the spoke’s head.
- Turn the loose spokes anti-clockwise and examine the inside of the rim as you tighten the spoke.
- If you need to loosen the spoke, turn the spoke clockwise. The direction is unlike regular bolts and nuts that use a clockwise direction when tightening.
- Remove the wrench and tap on the spokes to listen to the sound.
- If the sound is high pitched, this shows the spokes are properly tightened, but if it’s dull, you may need to tighten them again.
Change the Piston and Rings
The durability of the piston and rings depends on how you ride the dirt bike. If you are a weekend rider, the pistons will wear out gently, but for motocross racers, the pistons wear out faster. Other factors like track conditions will affect the longevity of the pistons and rings.
It’s best to change the piston in a 4-stroke dirt bike used for racing at least every 30 hours of riding. Although most people suggest that riding a bike gently can get you up to 100 hours of a 4-stroke piston, exposing the piston to tough conditions can break it. That’s why it’s recommended to change the piston every 50 hours when riding the dirt bike gently.
Replace Worn Out or Damaged Bearings
It can be challenging to know when bearings wear out, which is why you need to check them often and replace them once you notice something is out of place. You can check the wheel bearings by holding the dirt bike and trying to move the wheels from side to side.
Check the swingarm linkage bearings by placing the dirt bike on its stand. Take the rear wheel and try to move it up and down. The movement will point to the top rear shock bearing or the linkage bearing. Any wheel movement shows that the bearings need to be replaced.
To replace wheel bearings, you’ll need a screwdriver, a wrench to remove the wheel, punch, hammer, bearing retainer tools, and a bearing installer/socket.
Here are the steps to replace the bearings on a dirt bike:
- Start with a clean bike. Wash it to make your work easier and let you know if you have a leak or any other problem with your bike.
- Set the bike on a stand once it’s dry and remove the wheel that has the bearings you need to replace.
- Remove the seals with a screwdriver to get to the bearings. Get rid of the retainer and flip the wheel to remove the bearing. Take the punch and push the wheel space in between the bearings to hit the bearing.
- Hammer on the punch to knock the bearing out of the wheel. You want the bearing coming out straight. You’ll notice the wheel spacer out once the first wheel bearing is out.
- When installing new bearings, clean the area around the wheel and set it back on the stand. Take the wheel bearing and place it on the journal. Use a piece of wood to hammer the bearing in until its flush. Install the wheel spacer once you flip the wheel over to the other side.
4-stroke dirt bikes have multiple moving parts, which means they require lots of maintenance. These bikes are fast, powerful, and efficient, something that makes it ideal for trails and other races.
The above tips will help you understand how a 4-stroke bike works and how to maintain it to ensure the bike is simple to handle, easy to ride, and offers optimum power when maneuvering and controlling it.