Proper dirt bike maintenance is crucial to getting the most out of your dirt bike. You should always consult your owner’s manual as the following tips may vary from dirtbike to dirtbike. If the information presented here contradicts your owner manual, then you should trust the manufacture and abide by their recommendations. Furthermore we remind dirt bike enthusiasts to follow safe riding practices and ALWAYS wear protective gear.
What to do first?
It may be necessary to prime the carburetor before attempting to start it when the dirt bike is brand new, has been inactive for a long period of time, cold engine or runs out of gas. This is accomplished with the primer pump bowl located at the bottom of the carburetor. Simply press and release this pump several times until gas can be seen flowing through the clear gas return line to the fuel tank. This will help start the dirt bike under the aforementioned conditions. However, if this is done once the dirt bike has warmed up it may induce flooding.
How to adjust Carburetor?
The carburetor has many adjustments on it and it is recommended that these adjustments be made by experienced professionals only, however, we will point out the major points. The carburetor is responsible for pumping the fuel and mixing it with air at a precise measurement. The carburetor does this with very small diaphragms, orifices and ports, which are easily clogged by contaminants. This is why is extremely important that you use only clean new fuel in your dirt bike.
The small gold spring screw on the side of the carburetor is the idle speed screw. This screw controls the idle speed, The tip should extend about an 1/8 of an inch (4 mm). Adjust it so the engine will idle at a fast enough speed to stay running.
The brass color screw located below on the side of the carburetor, next to the choke lever is for the fuel and air mixture. Start by turning this screw (clockwise) until it stops. Don't turn it in tight, just until it stops. Next, turn the screw out two full turns (counter-clockwise). This is the factory setting. You should be able to start and operate the dirt bike with this setting. Once you have it running, you can adjust it. Never turn the screw more than 1/8 of a turn at a time. Turning it in too much will cause the motor to run lean at full speed and may burn a piston. Also, running too lean will cause a loss of low end power. Once you get the mixture set you can adjust the idle, it should be low enough that the engine doesn't vibrate. Finally make sure you have the choke lever down completely after the dirt bike is started and warmed up.
There is also a main jet adjustment screw dead center on the top of the carburetor. This is frequently set at 1 full turn out. If this is not adjusted correctly, your dirt bike may not run, or run very poorly. Once again, turn screw all the way in (clockwise) and then out (counter-clockwise) 360 degrees (1 full turn).
How to adjust your idle speed?
If the dirt bike will not idle or idles too fast, an adjustment screw is located on the carburetor next to the choke. Turning this screw clockwise will increase the idle speed. Turning the screw counterclockwise will decrease the idle speed. Remember that an idle speed that is too fast can be dangerous.
How to adjust the spark plug?
The spark plug is a crucial and vulnerable part on your engine. Your spark plug can be located on the top of the engine under the protective rubber boot. Your dirt bike comes with a tool kit containing a spark plug wrench for easy removal. The spark plug must be cleaned, and must be replaced promptly when signs of wear begin to show. The condition of the spark plug can tell you a lot about the performance of your engine. If the electrode is white, that can be a sign that your dirt bike is running too hot. This can be a result of either running too lean, or that the fuel and air mixture is too lean. If you are running your dirt bike to rich then your spark plug may be black, covered with gas, oil, or carbon. Another common problem is that the spark plug gets clogged up with carbon and/or oil and "fouls". This should be checked by assuring the electrode has a clean gap of .023 in.
How to adjust the air filter?
The air filter is used to clean the air going into the engine. Periodic cleaning of this filter is recommended to protect your dirt bike engine against the damaging effects of dirt and abrasive particulates. Your air filter can be located on the front of the engine and the protective cover can be removed with one screw. When the protective cover is removed the air filter is revealed. You can also see the small workings of the choke and butterfly valve. The filter should be free from dirt and grease and appear clean like the one shown on the right. If there are contaminants on the filter it can be cleaned in a container of gasoline. Allow the filter to dry before re-installing it into your dirt bike.
How to adjust the chain?
The chain on your dirt bike should be lubricated before every ride. The chain should also be checked for tightness on a regular basis. If the chain is too loose a popping sound can be heard and the dirt bike will jerk under acceleration, or the chain will just jump off altogether. If the chain is too tight it will be noisy and bind, this can be felt by pushing the dirt bike with the motor off.
How to adjust your throttle?
There are two main types of dirt bike throttles. One is a twist type, and the other is a hand throttle. Although the throttles are different in operation, they are essentially mechanically the same. When the rider applies the throttle, a cable carries this motion down to the engine. For continued smooth operation it is important to keep this cable clean and free of obstructions. Should the throttle begin to feel loose and sloppy, the slack can be adjusted on the cable at the handlebars. Simply loosen the lock nut and adjust the cable tension. Once the desired tension is achieved re-tighten the lock nut.
How to adjust the brakes?
The easiest way to adjust your brakes is on the handbrake itself. This adjustment has two simple steps. To change the tension on the cable simply loosen the locking nut to release tension. Once the desired tension is achieved re-tighten the locking nut.
How to avoid your engine from freezing?
Make sure there is oil getting to the piston and needle bearing areas. Certain oils can’t cling on when the engine get too hot. As a result, the needle bearing may fall apart inside and cause the engine to lock. You’ll have to buy a new engine or try to rebuild it. Be sure to always maintain proper engine oil levels to help prevent this from happening.
How to adjust your brakes?
Brakes can be tightened by the handbrake area by the handlebar or by the wheel area.
How to adjust your valves?
Checking and adjusting valves is considered a routine maintenance on four-stroke engines throughout the powersports industry. Valve clearance inspections are not hard to perform provided you have the experience and correct tools. If not, then it is highly recommended that you have these routine services performed by a qualified motorcycle mechanic as there is certain tips and tricks that can make the job go a lot smoother.
Whether you own a dirt bike, ATV, street bike, or any other four-stroke equipped machine. Chances are your owner's manual outlines when your engine's valve clearances should be checked. If not then you would need to check the service manual for your vehicle. Depending on the application, the inspection interval may vary from 15 hours to 15,000 miles. Checking clearances at the specified intervals is incredibly important to ensure the engine continues to run optimally and last a long time. Also as a rule of thumb, anytime the top-end of the engine is disassembled, it is best to practice checking the valve clearances.
To tackle this job, you'll typically need the following tools and supplies:
- Lash/Feeler Guages
- Metric Wrenches
- Metric Sockets
- Clean Rags or Towels
- Screwdrivers
- Caliper
In most cases, specialty tools aren't utilized. However, if they are used, you'll find that information in your service manual. A critical tool that is recommended is a set of feeler gauges.
Step 1: Since the engine is going to be partially opened up and exposed, it is best to work on a clean machine. If your machine is dirty, take the time to clean it thoroughly so the risk of contaminating the engine with debris is lessened. Prioritize cleaning the cylinder head cover and the surrounding areas.
Step 2: We'll begin outlining the procedure with the removal of the cylinder head cover. You'll likely need to remove your seat, fuel tank, and various other components before this. These items should be easy to remove and your service manual should provide sufficient guidance. When removing the cylinder head cover, be extremely careful not to allow dirt to fall into the cylinder head.
Step 3: Next, the valvetrain will need to be positioned so that the clearances can be checked. Most service manuals specify setting the valvetrain so that the piston is at the top dead center (TDC) on the compression stroke. Setting the valvetrain at this position ensures that the cam, or cams, are on their base circles and that neither the intake or exhaust valves are open. The base circle of the cam is the circular portion of the cam which does no influence valve lift.
Step 4: Set the engine on its compression stroke at TDC. Most engines have mating alignment marks on the crankshaft and engine case as well as the cam gear and cylinder head. It is imperative that you know and understand how to utilize these reference points because they are used to correctly set the cam timing after any valve clearance adjustments have been made.
Once you've positioned the cams correctly, valve clearance measurements can be made using lash (feeler) gauges. Lash gauge measurements can be tricky due to the surrounding geometry and inexperience on the user's part. To obtain the most accurate measurement, it is essential that the lash gauge is inserted between the tappet and valve as close to parallel as possible. To facilitate parallel entry, bend gauges as necessary so that their tips can easily slide between the tappet and valve.
Step 5: Adjust the clearance between the rocker and valve between 0.04mm and 0.05mm. Once you have set both to spec, reinstall the valve covers and seals.
