Why does my engine bog down when I open the throttle?
One of the most frustrating carburettor problems is when your engine bogs down as soon as you open the throttle. Instead of a clean, strong pull, the motor hesitates, stumbles, or even stalls. This is almost always caused by a fuel delivery problem inside the carburettor.
A carburettor is designed to meter fuel precisely depending on throttle position. If it’s not delivering the correct mixture, the engine can’t accelerate smoothly. Let’s look at the most common causes.
Common causes of throttle bogging
1. Lean mixture (not enough fuel)
•A blocked or undersized main jet can starve the engine of fuel.
•Dirty emulsion tubes restrict flow, making the mixture lean.
2. Rich mixture (too much fuel)
•If the float height is too high or the needle jet is worn, the carb may dump excess fuel when the throttle is opened, drowning the engine.
3. Accelerator pump problems (where fitted)
•On many carbs, the accelerator pump squirts an extra shot of fuel when the throttle is cracked open. If this pump isn’t working, you’ll get hesitation.
4. Incorrect needle height
•If the carb needle is too low, it won’t lift enough fuel on throttle opening. Too high, and it floods the engine.
5. Air leaks
•A split intake boot or loose carb mount lets in unmetered air, leaning out the mixture and causing bogging.
Why DIY fixes rarely last
While you can sometimes “mask” the issue by adjusting the mixture screws, real fixes mean stripping the carb, cleaning all jets and passages, checking float height, and reassembling with fresh seals. Many riders waste hours swapping jets blindly without solving the real issue.
Professional carburettor tuning service
That’s where a professional carburettor rebuild and tuning service comes in. With ultrasonic cleaning, proper jet inspection, float setting, and carb balancing, your engine gets exactly the right fuel at every throttle position. The result? Instant throttle response, better acceleration, and improved fuel economy.
💡 If your bike or classic car is bogging down on throttle, book a carburettor rebuild service near you. It’s the fastest and most reliable way to restore smooth, responsive performance.
