Hitting the gas full throttle should have you ripping down the trail at high speeds. When it doesn’t work that way and your machine responds with a muffled cry, you’re going to need to fix your ATV that’s bogging down. More often than not, an ATV that bogs down is experiencing an incorrect ratio of air to fuel.
While it sounds like a more advanced issue to fix, it’s possible to make the adjustments at home yourself and get back to a fully functioning rig. We’re going to talk a bit about why your ATV bogs down at full throttle, what the different types of bogging down are, and how you can go about fixing it at home without an expensive mechanic’s bill.
The air/fuel ratio of any engine refers to how much air is being put into the engine along with the mix of fuel. The ideal level is 14.7:1, meaning for every unit of fuel being injected, you have 14.7 times that much air. This level is tuned when in the factory, but can often find its way out of balance, making it up to you to fix.
As an engine ages, the carburetor will slowly move outside of the optimum mixture, which is why manufacturers installed an air/fuel mix adjustment screw. This is a simple and fast way to adjust the mix of air and gas so you don’t keep bogging down.
Before you get into the engine, you want to work on a warm engine, as this is when it’s operating at its best. Turn the engine on and let it warm up, then you can go to the screw. To make that adjustment, simply turn the screw clockwise for less fuel and counterclockwise to deliver more fuel.
Now, you need to be able to determine the difference in order to know which way to make your adjustment. There are two different types of air/fuel conditions that cause problems, rich and lean, so let’s look at how to tell what’s happening inside your ATV’s engine.
Rich condition is when your engine is receiving too much fuel for the amount of air being put in it. It’s overly rich in gas, so you need to make adjustments to deliver less gas with every intake. The common causes of the rich condition vary from the air/fuel mixture is incorrect, the air filter is clogged, having a carburetor float issue, or a leaky carburetor float needle.
You can identify a rich condition by bogging, spluttering, black smoke, or hard starts.
On the other hand, you have a lean condition. This is when you aren’t receiving enough fuel, making the ratio off and potentially causing bogging. With this, you may hear a popping or banging, the engine might not start, or you can only run with the choke engaged.
A lean condition can be caused by anything from bad fuel, an intake manifold leak, a faulty carburetor, or a blocked gas tank. The list is long, so diagnosing the issue and knowing what to fix can be a long process.
You can determine if you’re experiencing a rich or lean condition with a few small tricks.
Run the ATV while applying the choke. If the problem improves, you’re experiencing a lean condition, meaning you need more gas.
Next, remove the air filter and see if the bog improves. If so, your engine is in a rich condition and you need more air.
Another trick is to look at the spark plugs. A well-running engine will have a spark plug that’s a tan/brown color. If your engine is in rich condition, it will be black and sooty, while if lean, the spark plug will look much cleaner and gray or white.
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