Troubleshooting ATV Engine Problems
July 27, 2008 by ATV News
It happens every holiday season. You jam a bunch of food in your face, you feel bloated and you start to sputter before the night closes in. Once again, you’ve clogged up your system. Thankfully, it usually only takes a good night’s sleep and a little exercise to get your body up and running at peak efficiency again. Too bad keeping that precious ATV running at its top level isn’t as easy.
Just like your body, an ATV can get clogged up with all sorts of junk that makes it run completely out of whack. It’s going to take a lot more than exercising your ATV’s engine and letting it rest overnight to cure its issues. Most often tough starting, inconsistent idle and a sputtering engine are a direct result of poor maintenance. But don’t fret, it’s not too late to get your ATV running at peak efficiency again.
We’ve assembled several troubleshooting steps you should work through if your ATV’s engine and idle are hesitating like its driver after a holiday binge.
Step 1
This step may seem obvious to some, but one of the biggest causes of engine and idle hesitation is due to a clogged or damaged air filter. Recently, we were riding a 2007 Yamaha Wolverine loaner during a scouting mission and the quad started to choke up and sputter. After quick inspection, we realized the element was clogged with unacceptable levels of dust. The riding area had been in the grips of a drought and dust conditions were at all-time highs — air filter inspections should have occurred after each ride, but it was likely several weeks since the last time the Wolverine’s owner serviced the element. To get back to base camp, we gently rubbed the element on relatively smooth tree bark.
While many new machines come with a reusable element, older ATVs often don’t. If your machine’s element is damaged or excessively dirty like the borrowed Wolverine, replacement may be necessary. For reusable elements, soak in approved element soap and water, dry the element and ensure it is properly oiled before installation.
If symptoms persist, check the air filter housing for dirt and clogs. Finally, inspect the air filter housing-to-carburetor air boot for leaks. A damaged boot will cause the engine to suck too much air and run lean.
Step 2
It only takes a small amount of goop in the fuel valve or fuel line to cause problems and contaminate your ATV’s engine. Fortunately, cleaning the fuel valve (petcock) and fuel line is easier than cleaning out your polluted arteries after eating 12 deviled eggs at your aunt’s house.
Inspect the entire fuel hose for clogs. Turn off the fuel valve before detaching the fuel line. You can detach the fuel hose from the fuel tank and carburetor easily with a pliers to loosen the hose clamps. Visually inspect it for clogs. Any clogs can be taken care of with carburetor cleaner or products like SeaFoam. If the hose is cracked or damaged, replacement hose is very inexpensive and is available cut to length at most automotive retailers.
During this step, it is also advised to clean the fuel valve and, if your machine has one, corresponding fuel valve filter. A gummed up valve will result in fuel restriction and engine hesitation.
Step 3
Many regular unleaded fuels are blended with ethanol. Ethanol fuels have a cleaning effect on fuel systems and can loosen old varnish and other deposits, sending the debris through the fuel system where they clog filters, jets and other pathways.
If the gas has been sitting for a long period of time without a fuel stabilizer — generally over the winter months — drain it and replace it. Contaminated fuel is a large contributor to rough idle and hard starting. If you plan on storing your machine for long periods of time, use fuel stabilizer to avoid common issues found in the next three steps.
Step 4
Contaminated fuel can cause a host of other issues, including a clogged fuel filter and fouled spark plug. Remove your ATV’s fuel filter, unscrew the filter and inspect the brass screen. If it is contaminated, clean with STP, Gumout, Marvel or a similar product. If the fuel filter is damaged beyond repair, a new one can be purchased for roughly $10.
Step 5
As for the spark plug, a grayish-tan to white color indicates the plug is operating at the proper heat range. This also indicates correct jetting and that the cylinder is running well. Excessive electrode wear will cause misfires during acceleration and hard starting. A melted center electrode or chalky appearance could mean your machine is running a plug with the wrong heat range or there is a lean fuel mixture. Replace the plug with a compatible plug in the proper heat range. If the plug has an ashy appearance with light-brown deposits encrusted to the center electrode or ground, this is often the result of oil or fuel additives. Replace the plug and re-evaluate engine performance.
An oil-fouled plug could mean worn valve guides or piston rings. If this is the case, your machine could have low engine compression.
Step 6
So, you’ve jammed 1,000 deviled eggs into your pie hole over your lifespan and more greasy double cheeseburgers than you can fathom. The bad news for you is your heart is either going to stop or need quadruple bypass surgery. And worse yet, you might die.
The good news is operating on your ATV’s carburetor isn’t as complex nor as expensive when it’s obstructed, and it can be brought back to life. Unfortunately, for many machines, getting to the carburetor will be like cracking into a rib cage. But, once you locate the carburetor, removing it and cleaning it is a fairly simply process.
Like a restricted pulmonary artery in your heart will make you short of breath, debris barricading the main jet in an ATV’s carburetor will cause a lean, rough running engine and harsh idle. Generally, that debris is the direct result of gasoline and grime drying out, which leaves a thick goo residue or sediment build-up. Along with grime, small rust particles may have worked into the jets and orifices of the carb. These fine particles build up over time along with the dried up gasoline goop and the result is carburetor dysfunction — passages that direct proper air and fuel mixture are plugged or flow is restricted.
The only fix at this point is to disassemble the carb and clean the jets, sliders, diaphragm and float bowl. Taking apart a carb might sound intimidating, but it is a process most ATV riders with basic handyman skills can accomplish. The main tip here is to write down or chart where each part goes when taking apart the carburetor. Each part will need to be inspected and cleaned with carburetor cleaner.
If you aren’t confident enough to disassemble the carb, you can usually remove the float bowl without taking the entire carb and airbox off the machine. A gummed up float bowl is generally the culprit if the ATV’s rough idle or starting wasn’t diagnosed in an earlier step. Clean the bowl and main and slow jets with carburetor cleaner and use a toothbrush or similar bristle brush to clean the jets. Try to get a few of the bristles in the jet holes to unclog any impediments. Do not use wire as it can damage the jet size! You don’t want to accidentally re-jet your machine and cause more problems.
Finally, inspect the float bowl gasket and ensure it isn’t damaged. A bad gasket will result in an improper air-to-fuel ratio and unwanted fuel leaks.
Hopefully, the basic steps we’ve detailed will get your machine running at its peak performance again. The key is sticking to a strict maintenance routine. And, for your sake, avoid digesting 10 pounds of mutton next time you’re at mom’s house. For a comprehensive step-by-step carburetor cleaning how-to, see our upcoming May issue of ATV Magazine.
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Thanks guys, this was extremely helpful. My son’s ATV was not running at all, and it seemed to be a fuel problem, so I pulled everything above the carb off and then sprayed carb cleaner through it. It ran after that but with very little power. I read through this troubleshooting section and decided that I could take the carb out, disassemble it, and clean it. After I put it all back together (cleaning the airfilter and replacing all of the hoses while I was at it), this puppy ran better than new. Literally 20% faster than it was when we bought it.
Your advice was far more helpful than the manual.
My quad takes for ever to start and then when I get it started once i press the gas it won’t go I was gonna try everything on your web page but was wondering if you had any idea’s to why it’s doing this before i take it apart ? Thanks!
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