Sputtering and backfire
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4th Gear
Joined: Dec 2010
Posts: 8
Likes: 0
Sputtering and backfire
Hello I have an 04 1200 sportster custom. when im at idle roll the throttle it back fires from time to time then once i get going its fine. but once i get to higher gears like 4th or 5th it tends to sputter or "hickup" while you going. i wondering if any of you know what might be the issue. the bike is all stock and nothing has been modified.
Road Captain
Joined: Oct 2010
Posts: 566
Likes: 3
From: rural ontario
It is time for a tune-up. To be more specific is difficult. This could be caused by a fuel delivery problem resulting in a lean condition in the cylinder or a spark issue causing a misfire ( a slight crack in an ignition wire could cause a periodic short for example). I would start at the plugs and work back.
Just an after thought---your local gas station may have started using a higher ethanol blend and this could also cause problems like you are describing. Perhaps just changing to a higher octane fuel or new gas station would be enough to solve your problem.
Just an after thought---your local gas station may have started using a higher ethanol blend and this could also cause problems like you are describing. Perhaps just changing to a higher octane fuel or new gas station would be enough to solve your problem.
Elite HDF Member
Joined: Jul 2010
Posts: 4,828
Likes: 8
Doing a tune up will be a step in the right direction, for a few reasons. First, the new plugs will perform better than the used ones. Second, when you take the old plugs out you will be able to tell a lot more about what is going on with the air/fuel. The plugs will tell you if the bike is running lean or rich. Is it a true backfire (out the carb) or is it out the exhaust?
Also, what kind of exhaust are you running?
Also, what kind of exhaust are you running?
Elite HDF Member
Joined: Jul 2010
Posts: 4,828
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Could be a blown head gasket, too. A compression test will tell for sure.
Have you checked the coolant recently?
Have you checked the coolant recently?
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4th Gear
Joined: Dec 2010
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haha coolent, i have all new top end gaskets on the bike cause i had to replace a broken exhaust stud so i decided it all needed to be changed. im guessing it is a leak at the manifold but im going to check the timing and the spark plugs and wires just to cover all grounds. i have a stock California bike exhaust
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Elite HDF Member
Joined: Jul 2010
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Yeah, I would check the plugs and see what they say. They can tell a lot about the bike's air fuel condition. If they are tan, that is perfect. If the insulator is white or the electrode or ground strap are white or covered in white ash, it means the bike is running lean. If it is black and has a lot of carbon deposits on it, the bike is running rich. Also make sure that you put in plugs that are the same temperature replacement. Good luck, and if you need help reading the plugs, just shoot a pic of them here. Just make sure to mark them front and rear so you know which cylinder to look into.
If it is an intake gasket issue, only one of the plugs will show failure. If one is tan and one is white, you know it is a gasket issue. If one is covered in oil it could be ring failure, and if one is covered in black deposits it could point to valvetrain or piston holes or even piston compression ring blowby.
If it is an intake gasket issue, only one of the plugs will show failure. If one is tan and one is white, you know it is a gasket issue. If one is covered in oil it could be ring failure, and if one is covered in black deposits it could point to valvetrain or piston holes or even piston compression ring blowby.