Troubleshooting and PDI

 Troubleshooting Carb, Battery, and Fuse.

Checking for Spark/No Spark Troubleshooting




  1. Follow instructions on how to hook up battery, and assemble the rest of the unit. While assembling unit, charge the battery on a 12 volt, 1 to 2 amp trickle charger before first use. This will help to extend the life of the battery.
  2. FOR WHEEL ASSEMBLY (this is just a brief overview), the wheel goes on first, then the wheel spacer (kind of pushes up underneath the hub), then flange washer, then the castle nut (finger tight), then tighten the nut down further until you can insert the cotter pin through the hole in the castle nut and the hole in the axle, Insert cotter pin. *USE LOCTITE ON EVERY NUT AND BOLT ON YOUR ATV TO ENSURE NO LOSS OF PARTS OR FUNCTIONALITY DURING RIDES. ALWAYS CHECK FOR LOOSE NUTS AND BOLTS BEFORE RIDING.
  3. Use dipstick to make sure that there is enough engine oil filled to appropriate level, DO NOT OVERFILL or add more if needed. Your ATV uses REGULAR 4- Stroke oil 10W30, 10w40 or 15w40. Once it is broke in, after about an hour of use, change your oil again and then change about every 10 hours of use thereafter. NEVER ADD OIL TO LEFT SIDE OF ENGINE, ALWAYS ADD ON DIP STICK SIDE (RIGHT SIDE)
  4. Make sure the top of the carburetor (Throttle Body Top, it's a round cap that connects the throttle cable to the carburetor) is screwed down tightly and is secure BEFORE EACH RIDE. If this cap comes off your ATV will rev at full throttle during a ride and may cause a crash.
  5. Before you put gas in the gas tank, make sure to check the fuel line. Make sure it is connected and NOT KINKED from the gas tank, to the petcock, to the fuel filter, to the carb. In some instances it may be off the carburetor inlet. Add ¼ tank of gas, Use high 93 octane gasoline. Jets in the carb jets are very small and lower grade gasoline will clog them. Then on the bottom bowl of the carb, you will see a fuel line with a clear, capped fuel filter. Remove this filter and drain the carb bowl. See below picture…. (to drain the bowl, loosen this screw until all the gas has dumped out, use a bowl to catch the gas. You will see a yellow/brown/orange liquid come out with the gas, this is just packing liquid for shipping. Once this has all drained out, screw back tight, put the capped fuel filter back on the fuel line and fill the tank with gas)
  6. Make sure the throttle cable is pushed all the way into the top of the black rubber holder at the very top of the carburetor. AGAIN the top of the carburetor needs to be screwed down, all the way down.
  7. Turn on gas petcock (located on right side of carburetor, turn clockwise to on-it allows gas to fill the gas lines and the bottom of the carburetor. Make sure there are not any kinks in the fuel lines). Some models- this is not necessary because there is no gas shutoff valve=petcock.
  8. DO NOT USE THE REMOTE START TO START THE UNIT. ONLY USE THE REMOTE FOR ENGINE KILL/STOP. Put the key in the off position, then on the remote push unlock twice.
  9. Turn key to ON. To start the unit for the first time, you must use the key to start it and if you use the remote unlock to shut bike off then you must hit the unlock button twice before starting the next time.
  10. Raise the back end of the unit up and put a block under the back end. This is a good position to have it in as you make adjustments while starting.
  11. Fully choke the unit. We have two different models of chokes. One has the choke on the way to the left (fully choked), other type=Carburetor choke- slider should be all the way up (fully choked)
  12. For some models -Set the left hand brake (pull back on the left handle brake lever) and then push red button (kill switch) on left handle grip=THIS IS OUR #1 Problem, because if you cannot start it and you continue to give it more and more gas = Flooding the engine and running too rich which then deposits BLACK carbon deposits on your spark plug making it very hard to start in the future. For other models -Set the left hand brake (pull back on the left handle brake lever) and push red switch forward on left handle grip (rocker switch). ON black models-turn the gas shutoff (on right side of carburetor) on (lever needs to be down).
  13. Push starter button on left handle bar which is yellow on some models, it is a black button on other models, which is below the red kill switch.
  14. If when choke is on and you push the start button it will start up and almost immediately it will die. Then turn the choke off, then push start button and it will restart immediately and NOW work the throttle to keep it going while it warms up. (if you leave the choke up while running or idling you will FOUL your spark plug because you are too rich and the spark plug turns black).
  15. After starting, Let it idle for 2-3 minutes.
  16. Now you are ready to ride the ATV.
  17. Adjust maximum riding speed - When NOT riding the ATV, adjust the maximum speed control with the black long screw that sticks out of the right handle grip (see picture). When you loosen the screw, it increases the maximum speed, when you screw it in, it reduces the maximum speed. After adjusting the maximum speed to the desired setting, tighten the nut around the bolt tightly so that the bolt does not fall out. Also if the bolt is free to vibrate, it will change your maximum speed setting.



 It is definitely frustrating when you can't get your scooter or moped started. The first thing you'll need to do is to narrow down the problem. In order for your gas scooter to start, it really only needs 3 things:

  • Your vehicle needs to spark at the correct time.
  • Your engine needs the proper fuel/air mixture and exhaust flow.
  • You need sufficient engine compression.


Top 9 Reasons Why Your Scooter Won't Start:

  1. Try depressing the brake handle when starting.
  2. The battery has not been charged.
  3. The battery is hooked up wrong. This is often the reason for blown fuses
  4. There isn't enough gas.
  5. There is a gas flow problem.
  6. The spark plug wire is not connected.
  7. A low battery or bad relay can cause the vehicle to only start by using the kick starter.
  8. There is no spark to the spark plug. The coil is bad and needs to be replaced.
  9. Turn the key to the "on" position.


Compression Check

If you just acquired your vehicle, you should first do a full inspection before you try to get it running. If this is the case, I'd do a compression check first because it's easy to do.

  1. First, check the quantity and condition of the engine oil.
  2. Hook up or purchase a good battery.
  3. Leave out the spark plug and crank the vehicle for ~5 seconds. This helps to circulate the oil. Let it set for ~15 seconds and then do it again. It's not a good idea to continuously crank the starter because it can overheat and wear out prematurely. Most need a minimum of 100 psi in compression in order to run start and properly. Compression should be checked when the engine is warm. However, that's hard to do if it is not running. So, just hook up a compression gauge and open up the throttle all the way. Crank the vehicle until the needle on the compression gauge stops moving. This should take no more than 5 seconds. Very roughly, 100-125 psi is good, 125-150 psi is very good, and 150+ psi is great. If you don't have this level of compression, then you have bad valves and/or bad piston rings. If you want, you can add a teaspoon or so of oil to the engine through the spark plug hole. Then try the compression test again. If compression is higher, then it's likely you have bad rings. The oil will seal the rings and give you better compression. If compression is the same, then you have bad/misadjusted valves.


Got Spark?

You need to check for a spark. There are a few ways to do this. The easiest way is to remove the spark plug and put it back in the spark plug cap. Then ground it to the engine - you should be able to lay it against a non-painted portion of the engine. Make sure there is good metal-to-metal contact. In a semi darkened area, attempt to start the vehicle. You should see a definite spark at the tip of the spark plug. It's hard to see in direct light. If the color of the spark is blue, that means it's a strong spark. A white color is less strong, and a yellow color is weak. Most scooter/atv/go kart starting systems are a bit weak (compared to cars). Even a yellow spark should start your vehicle just fine. The spark must occur at the right time. Just about all made since around 1980 have an electronic ignition. These systems can rarely be set. In general, the spark occurs just before the piston reaches the top of it's stroke. There is a slight delay between the spark plug fire and the fuel-air mixture ignition. That's why the spark occurs a little early. Most ignition systems have an advance unit build in. As the engine speeds up, the time of the spark retards a little bit. This helps the engine fire the mixture at the proper time. Starting Fluid Assuming you have sufficient compression, try to squirt in a bit of starting fluid and then see if your scooter will start. If so, that's great! That means that you have sufficient compression and the proper spark. You should get the vehicle to run for a second or so on starting fluid. If so, there's a good chance you can keep it running. One caution here - do not run your engine for very long on starting fluid because it's hard on the engine.

Fuel/Air Mixture

The next thing to check is your fuel/air mixture. You could be getting too much or too little of either. If your vehicle has been sitting for a while, it's likely that the gas has evaporated and left a bunch of sludgy deposits. If it's been more than 3 months, you should clean out the fuel system and blow out (video above) or replace the carb. Disconnect the fuel line and drain the old gas. Add fresh fuel and make sure it flows smoothly through the petcock (on the bottom of the fuel tank). If the petcock is controlled by vacuum, you'll have to draw a vacuum on the vacuum line in order for fuel to flow. The vacuum line will be the smaller line on the petcock. Do you get a good, steady flow of gas? If so, good. If not, you will have to remove the petcock and clean it. The gas flow should stop when you release the vacuum.

Fuel & Vacuum Lines

Remove the fuel and vacuum lines that run from the petcock to the carb. Place a suitable container under the fuel line and draw air on the vacuum line to the petcock (if so equipped) and see how well the gas flows. The flow has to be more than a trickle. It should be steady and fairly substantial. If you get this flow, then you're ok. Run at least a pint of gas through to help flush the system. If you don't get a flow then it's likely your petcock is clogged. You have to remove it before you can disassemble and clean it. Carefully reinstall it on the gas tank or you could get a gas leak. Reassemble everything and try to start the scooter. It will take several seconds of cranking to get the gas to work its way from the gas tank to the carburetor. Spark Plug Install a new spark plug (especially if the engine is a two stoke). Clean or replace the air filter as necessary. The carb, air cleaner, and exhaust pipe are all carefully tuned to work together. Most vehicles absolutely WILL NOT run correctly if any of these parts are changed in a haphazard manner! Double check all connections, then crank your scooter for 10-15 seconds. Did it start? Do you hear any popping? It should sound like the engine is trying to run. Most vehicle will not start if you apply throttle while cranking. If the vehicle catches, but doesn't start, let it rest 15 seconds before trying to start it again.

The Speedometer

Most of the time a speedometer will quit working because your speedometer cable is broken. Most of the time, the speedometer cable breaks 5-6 inches from its connection at the front wheel. It tends to break here because of the bend in the cable and the exposure to the elements (water and dirt) near the front wheel. The good news is that new speedometer cables are cheap and are not difficult to replace.

I Have Trouble Getting My Scooter On Its Center Stand

Like most things, there is a technique to this. Even a small person can put a large motorcycle on the center stand with the proper technique. Here's what I do: Hold the scooter with your left hand on the left grip. Put your right (or left foot) on the center stand to hold it down. Put your right hand under the seat area, where there should be a railing or a grip. This is the place where you'll lift the scooter a bit. Now in one motion, push down with your foot while you tug back with your left hand and up lift up with your right hand. If you do all of these movements at the same time with the proper motion, you'll have zero problems.


How Can I Increase My Scooter Performance?

This is a common question with 50cc scooters, but it comes up a lot with bigger scooters also. The most important question is how much money do you want to spend. If you have a 50cc scooter, and you want to increase the top speed from 25 mph -> 50 mph, you might be better off to just buy a new scooter. As you increase the scooter's speed and acceleration, you will find that your brakes, frame, and suspension are probably not up to the task. Replacing all of these parts is quite expensive. If you just want a bit of increased performance for your 50cc scooter, there are probably carb, exhaust pipe, and variator (gearing) changes you can make. You might be able to find a big bore kit, so that you can increase the engine displacement from 50cc up to around 70cc. You might want to get a performance carb and/or a new exhaust pipe. You'll need to replace these two components (and probably the air box) at the same time to get the best performance increase. The engine is basically just an air pump. The more air you can move through the engine, the more power you get. Adding a bigger carb draws more air (and more fuel) into the engine. But you restrict the amount of added air if you don't change the air box. You also restrict the amount of air out of the engine if you don't replace the exhaust pipe with a bigger (or more free flowing) exhaust pipe. In addition, just changing the carb changes the fuel / air ratio inside the engine. Your engine may or may not like the change. For instance, the new carb could give you more top end power, but also lead to starting problems. Or it may run better at low RPM's and poor at high RPM's. Tuning for best performance can be a lot of work! Try to buy a scooter performance kit (carb, air box, exhaust pipe) that is tuned for your scooter. It will make things much easier. Lastly, add the big bore kit. This will give you more torque (pulling power) and better acceleration. It won't necessarily add top speed unless you make gearing changes too. For larger scooters, there aren't too many performance parts available here in the U.S. The easiest thing is to do a web search for "scooter performance parts" and see what you can find.

Scooter Performance Tips

  • You can also try replacing your worn drive belt. This will give you a few more MPH because a new belt rides higher in the pulleys.
  • Changing your roller weights. You can use just slightly heavier rollers for more top speed.  Adjusti your valves.
  • Install a new air filter.
  • Change the oil.
  • Put in a new spark plug.
  • Keep your tires at proper inflation levels. This also helps you get better mileage and prevent premature tire wear.


My Idle Runs Too High

This could be due to a throttle cable that is too tight or misrouted. It could also mean you need to turn the idle screw on the carb counterclockwise 1/4 turn. A high idle may be due to a vacuum leak. The rubber manifold between the carb and the cylinder head can crack over time. Try starting the engine and squirting some water around the carb, manifold, and vacuum hoses. If the idle decreases, you have a vacuum leak somewhere.


High Altitude Changes

This issue doesn't come up very often. However, at high altitudes (above 4000 ft), your vehicle will start starving for air. You'll need to place a smaller main jet in the carb, so that it will take in less fuel. A good rule of thumb is to reduce the size of the main jet by 10% and see if that works.