Popping on deceleration is due to unburnt fuel being ignited in the exhaust. The reason you do not hear this on a bike with a stock exhaust is due to the baffling of the stock exhaust. To REDUCE it may not totally go away popping on deceleration first make sure that you do not have any intake or exhaust leaks.
There are many ways to stop the bike from backfiring and some of them are as listed below. The engine will run clean if the fuel cannot flow properly and the main cause for this is a dirty carburetor. A backfire is caused by a combustion or explosion that occurs when unburnt fuel in the exhaust system is ignited, even if there is no flame in the exhaust pipe itself. That unburnt fuel can be caused by a variety of mechanical problems, and here are some of the most common reasons for a backfire : Running too rich.
Why does my scooter backfire? Category: automotive road side assistance. Most commonly backfires occur when the engine of your motor scooter is running rich. This means the mixture of fuel to air within your scooter is balanced too far in favor of fuel. During an incomplete combustion, the heat of your exhaust causes the surplus fuel to ignite and sparks a micro-explosion. Can bad spark plugs cause backfire? Why is my carburetor popping?
Is exhaust backfire bad? What causes backfire on acceleration? What does a backfire sound like? What causes a backfire through the intake?
What causes exhaust popping? What causes unburned fuel in exhaust? What does a popping exhaust mean? Why does my Chevy backfire through the carb? Why does my Chevy backfire through the exhaust? When you have a classic motorcycle that still has points and a condenser then things get a little more tricky because now not only do you have all those mechanical timing issues to worry about, but you also have to figure out if your ignition is manually timed correctly. My Triumph originally had a points system and I got tired of it so I installed an electronic system.
A point is basically two small metal discs that open and close as your engine spins around. Every time the discs separate it sends the signal to the ignition coil to send the spark to the spark plug. A point has to be set manually by following the written instructions from your motorcycle shop manual or repair manual. Once the timing marks are lined up you have to set the points a specific distance away from each other.
Again, this all depends on what model of motorcycle you have as they are all different. If your timing is off and the spark gets to the end of the spark plug a little too late then the exhaust valve in your cylinder head will have started to open, and the spark plug finally sparks. In order for the combustion process to take place successfully inside the cylinder there needs to be a certain amount of air and fuel. A rich condition on an engine is not a a healthy way to run and should be fixed.
Running rich not only drastically decreases your miles per gallon, but can cause severe backfires in the exhaust pipe. If there is too much fuel present in the cylinder when the spark plug ignites then not all of the fuel will be successfully burned during the combustion process, there will be excess fuel that is pushed out of the cylinder head through the exhaust valve.
This unburned fuel will come in contact with atmospheric air and be surrounded by the extremely hot exhaust header. In the presence of fresh air and high temperatures, the fuel combusts and creates a loud pop or bang sound. I was once troubleshooting a 2 cylinder motorcycle and each cylinder had a separate exhaust pipe. I would put my hand by the end of each exhaust pipe in turn to see how much air was coming out.
If one side is weaker than the other then you know you have a problem on that one cylinder. As I was reaching down to feel the air coming out, there was a loud bang and fire erupted out of the tailpipe, missing my hand by about an inch. I no longer put my fingers right by the exhaust pipe of a running motorcycle! The culprit of getting too much fuel in your cylinder is almost always the carburetor.
A dirty carburetor can cause a slew of problems. When the needle inside the carburetor gets dirty it tends to sticks to the walls next to it. When it sticks it lets in more fuel than intended and you get a rich condition.
Clean carbs should solve your problem of having a motorcycle running rich. For other ways to fix a motorcycle that is running rich, check out my article here. Just for clarification, a motorcycle exhaust header is the metal pipe connected directly to the engine, and an exhaust pipe is the last foot or two of pipe that can be disconnected or unbolted. I was once working on a BMW R80 for a friend and the threads on the backside of the cylinder head were damaged as usual.
We were having a hard time getting the exhaust nut to tighten down onto the cylinder head and finally we decided to just try it how it was. We started up the motorcycle and immediately there was loud popping coming from that side of the engine.
The exhaust was escaping around that loose exhaust nut. The exhaust gases leaving the engine have a lot higher pressure than the ambient air around us, so if there is even the slightest hole between the cylinder head and the exhaust header then the fumes will escape and create quite a noise. The best way to fix this is to tighten down your exhaust headers. Likewise, a fuel injection system performing improperly can cause backfires by failing to burn fuel completely.
Ray Byrnes began writing for publication in His work has been featured in "Buzz Magazine," online at the and in several literary journals. He specializes in writing fiction, poetry and journalism. He received his Bachelor of Arts in rhetoric from the University of Illinois.
Ignition Timing If the explosions in the scooter engine are improperly timed, it could result in backfiring. Fuel Filter and Injection System A poorly maintained fuel filter can also cause backfires.
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