Backfiring and decel pop - if you are a motorcyclist, you must have come across these two terms at least once in your lifetime. Chances are that you might have even experienced them while riding but you might not have been able to tell the difference. Well, let's understand these two terms and their impact on our beloved motorcycles from an experienced man in this industry, Ari Henning from Revzilla.
Let's begin by exploring why a muffler might emit sounds other than regular exhaust noise. During the combustion process in an engine, there will inevitably be some unburned gas left over. When this residual fuel mixes with oxygen in the exhaust, it can ignite, causing a phenomenon known as an afterfire. If the engine is not running optimally, this can result in combustion in the exhaust as well.
Two common types of afterfires are decel pop and backfire. Decel pop refers to a series of burbles, snaps, and bursts that occur when the rider rolls off the throttle, while backfires sound more like gunshots or firecrackers. While decel pop is a normal occurrence in modern street bikes, backfires are rare and potentially dangerous. They can cause the throttle body to detach from the engine or ignite the air filter.
In reality, what we often refer to as backfires are actually afterfires since they occur after the combustion chamber. Both backfires and decel pop are usually a sign of a problem with the bike's tuning, which could be due to issues such as a faulty injector, clogged carburetor jet, or messed up ignition or cam timing. If your bike is experiencing either of these phenomena, it's crucial to diagnose the underlying issue to avoid causing damage.
One factor that can contribute to decel pop becoming more noticeable is the installation of an aftermarket open exhaust, which reduces the muffling effect that the OEM pipes have. Additionally, larger muffler openings introduce more air into the exhaust, which can lead to more combustion before the gases are pushed out of the tailpipe. If decel pop becomes as violent as a backfire, it's essential to check for exhaust leaks and have the air-fuel ratio checked.
While decel pop is normal and harmless, backfires are a sign of trouble. In professional racing, however, it's common to maintain some fuel flow when the throttle is closed to improve initial throttle response. This, along with a wide-open exhaust and abundant raw gas, can result in flames shooting out of the tailpipe.
In summary, understanding the difference between decel pop and backfire is essential for maintaining your bike's health. While decel pop is normal and usually harmless, backfires are a warning sign that something is wrong with your bike's setup. If you're experiencing either of these phenomena, it's crucial to diagnose the underlying issue to avoid causing damage.