Why is one cylinder not firing?
When your bike is running on three cylinders instead of four (or one instead of two), it’s a clear sign something’s wrong in the fuelling or ignition system. If the plug on that cylinder is dry and pale, fuel isn’t getting through. If it’s wet and black, the mixture is too rich or the spark isn’t igniting properly.
On multi-carb bikes, it’s common for one carburettor to have a blocked jet, stuck float, or leaking diaphragm that stops the cylinder from firing. A split in the vacuum diaphragm can prevent the slide from lifting, starving that cylinder of fuel at anything above idle. On older bikes, perished intake rubbers can also introduce air leaks and throw the mixture off.
At The Carb Shack, we diagnose and fix these issues from the inside out. Every carb is stripped, ultrasonically cleaned, and inspected for jet blockage, slide wear, or diaphragm damage. We test each carb individually and bench-sync them to ensure balanced fuelling across all cylinders. The result is a smooth, even idle and crisp throttle response on every pot.
If one cylinder keeps dropping out, don’t keep swapping plugs and guessing. Book your carburettors in for a professional clean, rebuild, and sync. We’ll get all your cylinders firing perfectly again.
