Dirt Bike Won’t Start TroubleShooting

Fuel? Air? Spark?

1. Make sure the gas line is in the ON position.

2. Make sure that there is gas in the dirt bike.

3. Make sure the spark plug boot is pushed in.

4. Make sure you have spark. To test for spark, take the spark plug out from the head, but not out of the boot. Put it against some metal on the bike and turn it over while kicking the kick start (or if you have an electric start, use that). You should see spark. If you see no spark, then put a new spark plug in. Make sure to put the right size spark plug in and do not over-tighten the spark plug.

5. Use choke.

7. Spray Starting Fluid in the Carburetor

8. If the motor has not run in a long time (i.e. more than 1 year), you should put new gas in it.

9. Once you have done all of these steps and it still won't start, then clean the carbs.

10. Clean the air filter.

Air — This means a Clean Air Filter. A dirty air filter can easily result in a fouled spark plug, and If you haven't seen the air filter in a while, be sure to check out our article detailing: How to Clean and Maintain an Air Filter on a Dirt Bike, but also be sure to review the air tract evaluation tips below as this will help in evaluating the condition of the air filter and intake tract.


Fuel — Presuming there's gas in the tank (you can hear it sloshing, or you might've even looked inside) you need to ensure there's an adequate supply of clean fuel going to the carburetor which there is more below on fuel quality and fuel supply to the engine so that's a good place to start if you're suspecting that the motor's not getting fuel.


Compression — If you've got a dirt bike with little or no compression, you're wasting your time kicking or running the battery down and swapping spark plugs. Little or no compression generally means the top end is either pretty well done, or there's a leak around a sealing surface. If you're interested in learning about a compression test, you should probably take a look at the article elsewhere on Performing a Compression Test for more info on checking the top ends condition.


Spark — This is usually the first thing that everyone suspects when a dirt bike won't start, but this can also be misleading because a plug will frequently fire out of the cylinder, but under the pressure of being in a cylinder, a spark plug will frequently fail to fire and light the mixture. If you have doubts about the spark plug firing, put a new spark plug in the hole and see what happens, then if it still won't start, Check out our other tips on determining why the bike isn't firing.

 Adjusting the carburetor.


The idle screw is the screw on the carburetor with a SPRING around it. The air/fuel screw is the flat-head screw usually before the idle screw closest to the air filter. Some newer carbs have the a/f screw on the bottom of the float bowl. Here are some basic adjustments to get it started and to tune it once broke in.

The mixture screw had been set-up at the factory before shipment and should not have to be reset. Only a small adjustment may be needed due to climate and elevation. If necessary, refer to the adjustment as below: 

1. Make sure the air cleaner is clean.
2. make sure the choke lever is OFF while running.
3. Warm the engine up for 3-5 minutes.
4. Turn the mixture screw clockwise until fully closed,
then turn the mixture screw 2 full turns out.
5. Adjust the idling screw until the engine idles EASILY.
6. Turn the mixture screw slightly clockwise and
counterclockwise until the highest engine REVs is obtained.
7. Adjust the idling screw again until the engine idles
8. Repeat step 6 & 7 till you get the best 
The engine idling screw must be set correctly to get a
slowest engine idle(1500 rpm - 1600 rpm), but does not 
cut out if you press the accelerator quickly. 

Cold weather starting will need an additional adjustment to help aid the starting process. 

Most of the manual choke carbs have an adjustable needle inside the carb. Lowering the clip (raising the needle) you will be able to open the throttle and get more fuel into the intake quicker. This helps in the cold weather because the colder the weather the leaner the mixture is. You want richer in the colder weather.

1- Unscrew and pull the top of the carb off with the cable and there will be a slide with the needle in the center. (Notice the way the carb slide came out) In step #6 it must go back in the same way it came out.
2- Disconnect the cable through a small slot in the side of the slide. 
3- Now you can take the needle out from the slide. 
4- The needle will have a very small e clip in a slot on the needle. The needle will have 5 slots. Lowering the clip is richer the and raising the clip will lean it out. 
5- Put the clip on the lowest setting for cold weather. DO NOT DROP THE CLIP! They are very small and hard to find.
6- Reverse the process with installing the needle back into the slide, installing the cable, slide the slide back into the carb and screw the cap tight. Remember in step #1 how the slide came out. It MUST go back in the same way.
7- Now make any adjustments as stated above in the carb tuning.

Remember in step #1 and step #6 I said the slide must go back in the same way it came out? The slide will go in 2 ways. ONLY 1 way is the right way. If the slide is not put in the same way, upon start the quad will take off at full throttle. Make sure when you go to start the quad you have a hand on the kill tether or switch this way if it does take off you can dissable it. If this happens the slide was put back in 180 degrees out. This is very important for the safety of you and anyone standing in front of or around the quad.

Motorcycle Won't Start Troubleshooting:
Top 10 Things To Check When Your Motorcycle Won’t Start
  • Engine Cutoff Switch
Some riders almost never use their kill switch to shut down the engine but use the ignition key instead. However, the engine cutoff switch can be turned off by bumping it in the right way or maybe having a kid walk by and play with it. Either way, many riders have suffered the embarrassment of making their riding buddies wait while they struggle to figure out why their bike won’t start – all the while with the answer right under their nose.
  • Dead/Weak Battery
We’ll get the most obvious one out of the way first. The usual signs of a dead battery are extremely dim running lights that dim even more or go out completely when you thumb the starter. A battery that will no longer hold a charge is characterized by an inability to crank the starter for more than an instant. If your bike starts, lucky you. If not, well there’s always jumper cables. The other sign of a dead battery is the Click of Death. There’s just enough energy left in the cells to trigger the starter solenoid to send out a distress signal: dot dot dot, dash dash dash, dot dot dot.
  • Clogged Petcock

Yes, your petcock* should have a screen on its fuel intakes to keep it from clogging, but rust particles from your tank’s innards aren’t the only thing that can clog the petcock’s internal passageways. Corrosion within the valve itself can bung up the works. Try tapping the petcock with a screwdriver (or a small rock if you’re stranded in a parking lot) a few times to see if you can jostle the gunk loose. Hopefully, you’ve got a filter inline before the carbs themselves are clogged. Also, the vacuum line from the engine to vacuum controlled petcocks can dry rot, crack, and leak, keeping the engine’s suction from opening the valve. A little electrical tape over the crack might get you home in a pinch.

*Get your mind out of the gutter and back into the fuel system where it belongs. A petcock is a fuel control valve that turns the flow of gas off, on, and to the reserve position.

  • Clutch Switch
Some bikes require that you pull in the clutch lever, even if the bike is in neutral, in order to get the starter motor to spin. If the starter won’t crank – not even click – at all and the instrument lights are on (indicating that you’ve got at least some power), try squeezing and releasing the clutch lever a few times to see if you can make the switch happy. Also, make sure you’re pulling the lever all the way to the grip. If that still doesn’t work, you can go all MacGyver on it by bypassing the clutch switch and  jumping the leads with a staple, fooling the bike into thinking the clutch is pulled in.
  • Transmission in Gear
Furthering the clutch lever switch issue, make sure your transmission is in neutral. You may be pulling the clutch in, but a faulty switch may be telling the starter motor that you’re not. Bikes that don’t require that the lever always be pulled in may be made to start with the transmission in neutral.
  •  Kickstand Down
You’d be surprised how many times riders find – after double-checking their preflight list – the non-starting problem was caused by having the kickstand down. Go ahead. Fold it up. Since the bike won’t start, it certainly won’t hurt anything. Sometimes what happens is that even when the kickstand is all the way up, the little plunger switch that tells the ignition it is, is stuck. Time to get on your hands and knees with a toothbrush and some WD-40.
  • Something Blocking Intake or Muffler Exit
In the tall tales of stored motorcycles, there exists a whole category of stories about owners who try to start their motorcycles only to discover that someone – usually of the rodent variety – has taken up residence in their airbox or muffler. These squatters usually decide to do a little remodeling or move in a bunch of furniture to their home, thereby restricting the airflow.
  • No Fuel
File this one under, Duh. Just like when an object can often not be where your are certain you left it, check to see if there is fuel in the tank. Shake your bike back-and-forth while listening for the telltale slosh. Although it was always funny when Wile E. Coyote checked the tank with a match, use your smart phone’s flashlight instead. Once you’ve made sure you have fuel, check to see if the fuel pump is running on bikes that have them. Also, on carbureted bikes, open the float bowl drain to see if any of the gasoline from the tank is making it to the carburetors.
  • Loose Spark Plug Wire
So, your engine is cranking and cranking but not starting. You’ve checked for fuel. What else can you try? The problem with electrical issues is that they’re hard to see as you troubleshoot. So, unplugging and replugging connectors becomes necessary. So, if you can reach the plugs on your non-starting motorcycle, why not check to make sure they’re properly seated by…well, you know.

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