Why does my four wheeler keep back fireing and not starting?//

Check the spark plug for spark and check the plug to see if it is getting fuel or if it is gas fouled to much fuel

Check that the cam shaft is turning ( broken timing belt). run fault codes to determine if a position sensor has failed.

If you have fire to the coil but not out out of the coil, the coil is usually bad. However on mid 80's Hondas, there is another common, but little-known cause. The connector on the wire going to the spark coil gets loose, corroded or both. Pull the connector off and inspect the tab connector on the coil. This connection has to be the cleanest and best connection on your cycle. If the connector tab on the coil is not shiny, polish it with emery cloth and push the connector back on. If it is not the tightest connection on the Atv, squeeze the female connector so it makes a tighter fit when you push it on.
BTW in my experience, this is the leading cause of ignition failure on Hondas more than 20 years old with with CDI ignitions.
R. Liston, engineer, formerly with Honda America.

How long since the oil has been changed? Is the oil level OK? It sounds like you have a sticky valve that hangs open once in a while.

Your Charging system is not working. You may need to replace the alternator. The only reason it runs when you are hooked to a charger is your battery is not holding a charge and the alternator is not producing the electricity needed to fire the spark plugs. When you hook up to charger, you now have the voltage necessary to fire the spark plugs.

some four wheelers require a battery to run correctly. sounds like you need a new one.

if your four wheeler is back firing you may have water in your gas or your gap on the plug

check your compression. piston rings might be ate up and its time for a rebuild.

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2. Car Repair & Maintenance
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4. Drain Car Oil
5. How to Repair a Polaris Four Wheeler

How to Repair a Polaris Four Wheeler By Brianna Byrne, eHow Contributor Spark plug inspection and adjustment can be one way to repair a Polaris ATV.

Almost every vehicle needs regular servicing and repairs in order to continually perform at its best, and Polaris' lineup of four wheelers is no exception. The company has released dozens of ATV makes and models throughout the years, ranging from sporty racing quads to youth models to heavy-duty utility ATVs. Despite the differences between the company's many makes and models, general repair tips and troubleshooting instructions remain consistent for all Polaris four-wheelers. The electrical, ignition and fuel systems are some of the most common sources of Polaris ATV problems.

Read more: How to Repair a Polaris Four Wheeler ' eHow.com http://www.ehow.com/how_8074861_repair-polaris-four-wheeler.html#ixzz26pmQIzeh

If the motor has two carbs then balance the carbs. Balancing the carbs basically means being certain the slides on both carbs open up simultaneously. If one carb opens sooner than the other then it 'drives' the other carb and can cause the backfire. Other things can can cause a backfire but lets start here first.