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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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!