Jul 05, 2016 If you mean it ran fine previously, and now when you ride it, it backfires? Or do you mean that it backfires unpredictably? It also matters what you are doing with the throttle when it backfires. There are two types of “backfire” — only one is tec.
.A backfire is a loud pop or bang sound that comes from your exhaust pipes when your motorcycle is running. A motorcycle exhaust backfire is an annoying and potentially dangerous problem to have. It can damage your ears if you’re in a confined space, or could start a fire as some backfires even emit flames, I’ve almost had my hand burned once from a pesky backfire problems I was troubleshooting.Why is my motorcycle backfiring?
A motorcycle backfire happens because of the presence of uncombusted fuel in the exhaust pipe. This issue is caused by:. Incorrect timing.
Too much fuel. Loose exhaust pipe. Too short of exhaust. Too little fuel. Intermittent sparkI have worked on dozens of motorcycles over the years and backfire issues seem to come around every once in a while.
I have a minor in automotive engineering and spent time in some of my classes studying and fixing backfires.I’ll describe each possible scenario as simply as possible so you can troubleshoot your motorcycle and try to understand why you might be experiencing this problem. Incorrect TimingWhen it comes to troubleshooting motorcycle issues, it’s always nice to have the right, basic tools handy so you can make these fixes in the comfort of your own garage.
To see my list of recommended tools to use on your motorcycle.Motorcycles have two different types of timing, either electronic timing or a points/condenser setup. Most motorcycles from 1970 on have electronic timing which makes things a lot easier.Electronic timing has simplified how to troubleshoot a backfiring problem because there are less parts to check off as the culprit.
The way electronic timing works is by sending a voltage signal to your ignition coil when one of the cylinders is in its compression stroke and about ready to fire.When the ignition coil receives this voltage signal it dumps its built up voltage which is carried through your spark plug wire, through your spark plug, and finally ends up as a big spark right at the top of your cylinder.Electronic ignition modules generally do a great job at sending the firing signal, even when they’re 40 years old.
A backfire is caused by the buildup of un-burned gasoline in the exhaust header and pipe system. Once the gas has built up to the right mixture with air, it explodes, making a loud bang. A visible flame may momentarily shoot out of the exhaust pipe.It can happen when you start your motorcycle, for example if you stopped the bike with high rpm’s and extra gas was left in the carburetor, when you accelerate or let off the throttle. Typically backfiring results from various malfunctions related to the air to fuel ratio.A backfire can occur in carbureted engines that are running lean where the air-fuel mixture has insufficient fuel and whenever the timing is too advanced.
As the engine runs leaner or if there is less time for the fuel to burn in the combustion chamber, there is a tendency for incomplete combustion. The condition that causes this is a misfire. The result of a misfire or incomplete combustion is that unburned fuel is delivered to the exhaust where it may ignite unpredictably. Another backfire situation occurs when the engine is running rich, meaning with excess fuel, and there is incomplete combustion, with similar result. Backfire is rare with fuel-injection and computer-controlled fuel mixtures. Actually, deceleration popping (backfire) is caused by a lean condition.There is always some unburnt fuel in the exhaust gases. (we never have perfect and complete combustion, if we did the EPA would love it) These leans gases are above the flash point of the gasoline.
So if the unburnt fuel gets next to any free oxygen before it cools below the flash point, it self ignites and we have decel popping.This is why when you install a free flowing exhaust system on a engine you often aquire decel popping. It lets reversion air up the pipe where it was too restrictive in the stock exhaust system to get in before.That is why when you richen the mixture decel popping goes away.