One of the most common power robbing culprits on an ATV is a dirty air filter. If you spend even a little time riding your ATV in sand dunes there's a very good chance you need to clean yours.
Unlike street vehicles, the air intake on a machine designed to traverse dirt must not only provide the motor with oxygen to make the appropriate fuel-air mixture necessary to propel the bike forward; it must also keep dirt, sand, gravel, and all other manner of potentially dangerous material out of sensitive moving parts within your motor. This section of your machine balances performance and protection more than any other.
In addition to being a potential hazard (a little slug of sand or gravel into your engine will end your trip with alarming speed and finality), the accumulation of dirt and grime within your intake system can make it harder for your motor to pull in needed oxygen, actually robbing you of horsepower better spent on making the wheels spin really fast.
Taking a few minutes to remove and clean your air filter and air box at the beginning of a new season will go a long way to allowing your bike’s motor to reach its’ maximum potential.
Specific cleaning directions follow:
To start, pull off your bike seat and other plastics/parts as necessary to be able to really get in and work around the intake system. You don’t want anything impeding your work and the areas around the intake can sometimes be a tight fit. Check the current level of grime build up in and around the filter.
Take a can of WD40 or other agent to clean and remove dirt and grime from around the intake port (the place where air is drawn from the filter/air box to continue towards the carburetor, usually via a shaped plastic intake tube).
Make sure this area is thoroughly clean of excess dirt and grime. Once that is done, remove the entire airbox/intake assembly as one piece. Make sure to saran wrap (or otherwise protect) the now exposed intake port, to prevent any grime floating around in the air or around the shop from getting into the exposed motor.
At this point you should have just the airbox and air filter separate from the bike itself. You can now more easily remove the air filter and not worry about where any of the built up grime or dirt may go as you unscrew and/or jostle the filter loose from its’ fitting inside the air box. Remove the filter from the air box.
If you have an outerwears cover over your filter remove it (An outerwears cover is a polyester cover that slides over the air filter. It is usually used on aftermarket, K&N style wire mesh filters as an added layer of protection to catch fine grain dust and sand. These are usually unnecessary unless you’ve either removed your airbox lid and/or the entire air box leaving the filter exposed to the open air).
Now you should have the air box and the filter lying separate. The filter itself should be cleaned using a filter cleaner (foam filters have foam filter cleaners, and K&N mesh filters have a specific filter cleaner. MAKE SURE you’re using the right cleaners and oils for the right type of filters).
After the filter has had a chance to be cleaned with the correct type of cleaner it should be re-oiled. Again, as with the cleaner, make sure the filter oil you’re using is the appropriate type. For mesh-wire filters it is ESPECIALLY important that when applying oil you make sure at least a thin layer covers each ridge line on the filter’s surface.
The best way to do this is to hold the filter oil can about 6-9 inches from the filter, and apply an even stream up and down each line of the filter while slowly turning it on your hand to ensure that every inch of surface area has a nice thin layer of oil. Once you’ve done that, set the filter aside to dry.
The airbox (and the outerwears cover if you have one) should be thoroughly cleaned and de-greased. You want to ensure that none of the old oil, dirt, and grime find its way back into your machine.
Plenty of de-greasers and cleaners are available that can handle the job; I prefer simple hot water and dish soap. Thoroughly rinse and scrub the airbox free of any visible build up of dirt. Once the airbox is thoroughly clean, it too must dry before placing back in the bike.
Once everything is cleaned, oiled, and dried, you can reassemble everything as you found it. I would recommend putting the airbox in FIRST, thus giving you some extra hand space to ensure everything is reconnected properly.
Pay special attention to the connection point between the air box and the intake. The connection must be sealed and flush, devoid of any dirt or other impediments. This area is also a good place to inspect if you're buying a used ATV because it can be a strong indication of how the ATV was maintained by the previous owner(s). Once you’ve reinstalled and secured the airbox in place, you can start in on the filter.
If you have an outerwears cover I recommend sliding it back over the filter before re-installation of the filter. Once that’s done, place the filter flush in its seat and tighten into place (varies dependent on model, but this is usually done with a clamp controlled by a Phillips screw).
Once you’ve done that, BEFORE you replace the plastics and the seat, fire up the machine and give it a few revs. While you do that, place your hand around the connection points on the filter and airbox and feel for airflow. Air being pulled through the filter = good, air being pulled in AROUND the filter (i.e. bypassing the filter via the intake port air box or elsewhere) = bad.
Once you’ve run your test, you’re ready to rock! Your ride will definitely appreciate the added lung capacity the next time you stomp on the throttle.