In a rich air-fuel mixture, fuel amount will be in excess and in a lean air-fuel mixture, air will be in excess amounts. When there is too much air in the engine, the fuel gets clouded by the air in the combustion chamber and as a result, does not get burned completely in the engine. This unburnt fuel when reaches the exhaust will then detonate to cause backfiring in the motorcycle. Whenever a lean air-fuel mixture is causing problems in your bike, you need to look into these two things:.
Check both the carburetor as well as the inlet valve which is causing low fuel entry into the engine. Once the issue is addressed, the motorcycle backfiring will stop automatically.
Spark plugs are important engine components used to ignite the compressed air-fuel mixture in the combustion chamber. If there are deposits formed on the spark plug layer, then it would be difficult for the plug to ignite the engine.
The deposits block the spark plug to generate spark in the combustion chamber. As a result, a masked spark plug can cause uneven ignition inside the combustion chamber, with most of the fuel leaving the engine unburnt. This unburnt fuel, upon reaching the exhaust pipe, will detonate — to cause motorcycle backfiring.
Spark plugs need to be checked every to miles of distance traveled. You need to keep the spark plugs in good condition by checking it regularly during every motorcycle servicing. If a masked spark plug is the problem and is causing backfire, then you might have to replace the spark plug entirely.
To determine whether you need to replace the spark plug or not, check the spark plug gap using a wire type feeler gauge. The spark plug gap should fall within the tolerance limits specified by the manufacturer. Typically, around 0. If the gap is less than the tolerance limits, you have to replace the spark plug with a new one.
Another reason why your motorcycle backfires is because it has a high flowing exhaust system. If your motorcycle has a larger opening at the back and a short pipe, then it has high flowing exhaust system. Decel backfiring, i. Shorter the length of the exhaust pipe and larger its opening, higher is the air flowing in the exhaust.
On a high flowing exhaust system, where air can enter the exhaust easily, a high amount of decel backfiring can be experienced in the motorcycles.
If the backfiring is because of high flowing exhaust in your motorcycle, you need not worry much. If at all you want to address it, you can replace the exhaust pipe with a large one. Again, this is not at all required. Dirt accumulation in the jets will prevent sufficient fuel flow in the carburetor. This in turn will lead to a lean air-fuel mixture entering into the combustion chamber. So, dirt in the jets — pilot jet, main jet and needle jet — in any of these, will ultimately lead to backfiring.
Even filling up every-now-and-then using higher octane fuel will help to clean out the fuel system. All jets should be removed and cleaned using carb cleaner , as should the housing of the carburetor. If you ride in dusty or muddy conditions for example: motocross, dirt bike, enduro and adventure riders , you need to start doing more regular maintenance. Make sure you clean your air filter regularly, lube it, and seal it to the airbox housing with a thin layer of grease.
Simple answer? A backfire is a fuel malfunction. Any combustion outside of the combustion chamber is going to result in a loss in power. Sometimes you can really feel the cut out of power for a brief moment. Running the motorcycle too rich or too lean can also cause the internal temperatures of the combustion chamber to get too hot and fry your engine! Uh Oh! One of the easier things to check off the list would be the spark plug.
The spark plug is responsible for the ignition and it might have bad ignition timing with the compression. Sometimes the issue can be as simple as the levels of Octane in your fuel.
I recommend running a higher-octane fuel through the engine to help clean out the fuel system and possible put a halt to those backfires. I recommend always using a premium high octane fuel for your bikes. This applies to engines that use a carburetor for its fuel management system instead of fuel injection. If your motorcycle has sat for a lengthy amount of time then it is very possible the old gas has sat in the carburetor and the impurities have settled, causing a clog and your engine to run poorly or maybe not run at all.
Your carburetor has 4 components inside that make all the magic happen when you get a hand full of that whiskey throttle. If you think that you need to clean the carburetor then you need to go buy a can or 2 of carburetor cleaner, it will come in a spray can with a straw attachment.
If you have done all of this and are still experiencing backfiring problems then you more than likely have an air flow issue. On many older carburetors there are idle and mixture screws that could also need adjusting. If you have an aftermarket exhaust I would try swapping the stock exhaust back on the bike and see if the backfiring persists.
There are a few different methods you could go about checking for an exhaust leak. If you have access to a smoke machine then here is a video demonstrating how to perform that method.
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