Occasionally when we're riding and come off the throttle, we hear a loud popping. This is particularly noticeable if you've installed a new exhaust system or jet kit. In this month's tech talk, we'll explain what causes decel pop, whether it hurts your bike, and what you can do to reduce it.
If you have a carbureted bike with a big single cylinder, decel pop is inevitable. It happens when you chop (turn off) the throttle while the motor is still moving at high RPMs. The strong vacuum created by the moving piston forces fuel through the choke/idle circuit and through the engine. When the raw gas comes out the other side and hits the hot exhaust pipe, it ignites and goes boom. It might be annoying, but it doesn’t hurt anything in the motor.
We often hear about this issue right after someone installs a new exhaust system and/or a proper jet kit. While the decel pop was always there, the stock jetting is usually lean enough and the stock exhaust strangled enough that you don't notice it. So as you can imagine, you can also reduce the decel pop effect by changing the jetting to achieve a leaner mixture. Unfortunately, doing so will often also negatively impact performance, and the pop never goes away completely. Another remedy is to slightly alter your riding style. Rather than chop the throttle, if you take a moment to roll off smoothly, it will greatly reduce the vacuum in the intake circuit and reduce the decel pop.
Check out the full video to learn more about decel pop and other common carburetor questions!
