How to keep Cobra Exhaust from Back Firing

How to keep Cobra Exhaust from Back Firing
Most people who install Cobra Motorcycle exhausts end up complaining about backfiring at some point in time. Backfiring is a common issue in most aftermarket exhausts so it should not worry you so much if it happens. This article will look at what backfiring is, what causes it and how it is fixed.
Cobra street bike exhaust

What Causes It?

Backfiring of the exhaust system is caused by the very same elements that cause engine combustion. These are fuel, oxygen and ignition. Backfiring of the exhaust during accelerations points to engine related problem and may not be easily fixed with fuel/air mixture changes. This is because it normally reflects problems with the valve seal, cam timing among others. Backfiring during deceleration is the most common one and is mostly a result of changes in the exhaust and fuel mixture. In this article, we will look at backfiring during deceleration.

Before looking at the backfiring bit, we need to understand how the whole system works. When you decelerate, the fuel injection system turns off right when the throttle is fully closed. When the engine reaches a predetermined rpm, the fuel injection system is turned back on. For motorcycles that backfire through the whole deceleration process, the injector may be the one with the problem and may not be turning off as expected. This shows it’s a fuel injection system problem.

Cobra Harley bike exhaust
There are many possibilities that can explain this including problems with throttle cable adjustment, Throttle Position Sensor among others. If backfiring is only present at lower rpm, this shows that the injectors are working properly and fuel is igniting in the exhaust due to the oxygen present.

There are many ways that oxygen can make its way to the exhaust system especially for those using the Cobra V-Twin exhausts. To keep this in check, examine the bike and the exhaust itself to make sure they are both working properly. If the exhaust experiences very short baffles, this may be the cause as fresh air makes its way in along the sides of the pipe. This is very common in short exhaust pipes with large diameters.
Cobra Harley bike exhaust

Tests to Fix Backfiring Issues

When the engine is fully warmed, decelerate and listen to where the backfiring occurs and then fix it.

Add some fuel to the cruise range and ride the motorcycle to see if there are any changes.

On short open pipes, try increasing the baffle effect and see what happens.

For motorcycles with exhaust gas re-circulation systems, unplug the feed tube and see if any changes occur.

By: James Langston
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