This publication explains the reason for your motorcycle popping on acceleration. When this happens, you get a loud popping sound under moderate to hard acceleration from your front cylinder.
Perhaps, the exhaust is coming out of the compression release but if they look normal, it may not be the exhaust, and you will not find exhaust residue at the exhaust port. In some cases, you may not even notice oil leaks or any signs of a blown head gasket—at least not yet developed.
Motorcycle popping on acceleration
Some of these causes are fixable yourself but it’s usually advisable to have a mechanic diagnose and fix the problem. Below are the reasons your motorcycle pops on acceleration:
Intake manifold leak
It will take just a minute to check if there is an intake manifold leak. The popping noise could come from an air leak somewhere—intake or exhaust. You could bet it is the intake.
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Check and ensure that the intake manifold (rubber) is soft and pliable. If the manifold is hard and cracked, there could be an air leak at the manifold. The common symptom would be high idle that falls slowly to normal.
Try to remove the small aluminum plug on top of the carburetor between the top of the carburetor and the manifold boot. You should find an air screw there. Adjust the air screw by turning it halfway and testing it. Keep repeating this until the motorcycle popping on acceleration stops.
The cause of the pop when accelerating your motorcycle could be a positive wire from the battery to the solenoid getting too hot. It can make a bad connection and cause your bike to surge badly during acceleration.
You want to check the connections to the ignition module and ignition module grounds at the frame.
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Inspect the battery negative ground strap. If it is loose, that could be the reason your bike is popping loudly.
The problem could also be the connection from the voltage regulator to the starter on the primary case. If it has a bad connection, it will be cutting in and out, so the connectors will toast and melt. You need to buy a voltage regulator and starter for your motorcycle to run like brand new.
Blocked fuel filter
A blocked fuel filter could be the reason your motorcycle pops on acceleration. The solution is to clean or change the filter. Your engine uses more fuel when hot, so the blocked fuel filter is unable to give sufficient fuel to the engine, causing the popping noise when you match the gas.
Blown head gasket
The head gasket sits between the cylinder head and the block, where it seals the two mating surfaces of the top and bottom halves of the engine. Unlike other engine gaskets, the head gasket has to seal oil, coolant, and compression from the cylinders simultaneously, making it the most stressed gasket in an engine, and one of the most likely to fail.
You want to make sure the intake gaskets are good. Sometimes, a blown head gasket will chirp when you start the engine.
Sucked in carburetor pipe
The seal on the Y-pipe for the carburetor can get sucked in. You have to replace it with richness. After re-jetting again, it could be good for a short time before sucking in again. You can hold it with a windshield.
The simple cause could be that something did not seal when you did work on your carburetor. You have to pull it apart and check for it again. It could even be a tiny problem resulting from over/under-tightening some parts or getting gasket material in the way or not in the correct position.
This may be too technical for you to fix, so get someone who is good at rebuilding carburetors. You could use carburetor cleaner to blast out the air and fuel in the carburetor body.
Bad fuel or water in fuel
Bad fuel or water in the fuel can affect the engine, causing a popping sound when accelerating your motorcycle. Check to see if you bought fuel with ethanol in it. Here’s a video guide to tell if there’s ethanol in your gas:
Bad gas will make your motorcycle engine run erratically. And when gas is mixed with ethanol, it can go stale in about 30 days, according to Champion Auto Parts. Ethanol attracts moisture over time, which dilute the gas causing your motorcycle to pop.
Dirty spark plug
Perhaps, you already checked your spark plug, but do you have the right spark plug? Some spark plugs are hotter or colder than others.
If your dirty spark plug is black and sooty, you are running rich and need to either lean out your mixture or double-check your air cleaner, making sure it’s in good condition.
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It should only take a few seconds to pop off the side panel and brush them off. You will experience a noticeable difference in sound and power on acceleration after this fix.
An exhaust leak can cause a popping noise when the motorcycle accelerates. An easy way to check if an exhaust leak is the cause is to run the bike for a while—let it idle and tightly plug the end of the exhaust with an old towel.
If your motorcycle stalls, there is no exhaust leak. But if the motorcycle sputters and runs rough, there could be a leak in the exhaust.