EFI to Carb Conversion: Is It Worth It?

The automotive world has seen a significant shift from carburettors to Electronic Fuel Injection (EFI) over the past few decades. While EFI offers benefits in terms of emissions, fuel efficiency, and precise engine management, there remains a segment of riders who yearn for the simplicity and adjustability of traditional carburettors. This has led to a common question: can an EFI motorcycle be converted back to carburettor setup? The answer, for many models, is a resounding yes, but it's not always a straightforward or universally beneficial modification. Let's delve into the intricacies of EFI to carburettor conversions.

Why Convert from EFI to Carburettor?

The primary drivers behind considering an EFI to carburettor conversion often stem from a few key areas:

• Perceived Complexity: EFI systems, with their sensors, injectors, and electronic control units (ECUs), can seem daunting to understand and maintain, especially for those accustomed to the mechanical nature of carburettors.
• Cost of Repair: When EFI components fail, replacement parts can be expensive. Some owners fear the potential cost of diagnosing and repairing EFI issues.
• Tuning Limitations: While EFI offers precise control, some riders feel it can be restrictive when it comes to aftermarket tuning, particularly with modifications like exhaust systems and air filters. They might prefer the hands-on approach to tuning a carburettor.
• Nostalgia and Simplicity: For many, the appeal lies in returning to a more 'analogue' riding experience. The simplicity of a carburettor, with its readily accessible jets and adjustment screws, appeals to those who enjoy tinkering and understanding the mechanical workings of their bike.
• Component Failure: In some cases, EFI systems can become unreliable, leading owners to seek a more robust or familiar solution.

EFI to Carburettor Conversion Kits: What's Involved?

Several manufacturers and custom shops offer conversion kits to facilitate this transition. These kits typically include the essential components needed to replace the EFI system:

A notable example is the Amal Carburettor Conversion Kit for EFI Royal Enfield models. These kits often include an Amal MK1 Concentric carburettor, filter, petrol tap, adaptor plate, cables, and gaskets. Extensive dyno testing has shown that these conversions can lead to good increases in both torque and BHP, allowing users more freedom to use different exhausts and air filters without EFI system restrictions.

For models like the Harley Davidson, kits are available to remove Magnetti Marelli EFI systems and replace them with carburettors, often including all necessary parts like manifold, air cleaner backing, standalone ignition, carb, seals, fuel pipe, and choke cable. Happy customers report significant improvements in tickover, power, and acceleration.

Is it Always a Good Idea? The Counterarguments

While the allure of carburettors is strong for some, it's crucial to consider the potential downsides and the advantages of modern EFI systems:

EFI Advantages

• Emissions Compliance: EFI systems are far more effective at controlling emissions, which is increasingly important for meeting stringent regulations like MOT tests and Low Emission Zone (LEZ) requirements, particularly in urban areas like London.
• Fuel Efficiency: EFI generally provides better fuel economy due to its precise fuel delivery.
• Performance Across Conditions: EFI systems automatically adjust for changes in temperature, altitude, and air pressure, ensuring optimal performance in a wider range of conditions without manual adjustment.
• Easier Cold Starts: EFI systems typically provide a richer fuel mixture when the engine is cold, leading to easier and smoother starting.
• Engine Longevity: By maintaining the correct air-fuel ratio, EFI can contribute to reduced engine wear and potentially longer engine life.
• Tuning Potential: While some feel EFI is restrictive, modern EFI systems can be remapped or fitted with piggyback units (like a Power Commander) to achieve significant performance gains, often exceeding what's achievable with carburettors, especially for highly tuned or forced-induction engines.

Challenges of Conversion

• Emissions and Legality: As mentioned, removing an EFI system can make it difficult or impossible to pass emissions tests. Modifying a vehicle to bypass emissions controls can also have legal ramifications and affect its roadworthiness.
• Complexity of Integration: Not all EFI bikes are straightforward conversions. Some engines may rely heavily on sensors integrated with the EFI system for ignition timing or other critical functions. For example, some motors might not have easily adaptable crank sensors for older standalone ignition systems.
• Inlet Manifold Design: The biggest physical challenge can be fabricating or sourcing a suitable inlet manifold to connect a carburettor to an engine originally designed for EFI.
• Fuel Pump Requirement: EFI bikes typically have an electric fuel pump in the tank. This needs to be bypassed or replaced with a gravity-fed fuel tap, and the carburettor's float bowl needle valve must be capable of handling the fuel supply without leaking.
• Loss of EFI Benefits: You lose the inherent advantages of EFI – precise fuel control, automatic compensation for environmental factors, and potentially better fuel economy and emissions.

Case Studies and Opinions

Royal Enfield Owners

Royal Enfield owners, particularly those with models like the Continental GT 535, have shown a strong interest in carb conversions. This is often driven by a desire to personalise their bikes with aftermarket exhausts and filters, areas where the stock EFI could be perceived as limiting. The availability of kits like the Amal conversion allows them to tap into the vast aftermarket support for carburettor tuning.

Harley Davidson Riders

The sentiment among some Harley Davidson owners mirrors this. The Magnetti Marelli EFI systems on certain models have, at times, been a source of frustration, leading to conversions to carburettors for perceived reliability and a more classic riding feel. Testimonials suggest that these conversions, while not always cheap, can revitalise older bikes and improve their performance and rideability.

General Discussion Points

Discussions online reveal differing viewpoints:

• Some see EFI as a "black box" that is unalterable, while others point out that EFI systems can be altered with tuning boxes or remapping, offering a different kind of adjustability.
• The debate often touches on the "point" of EFI versus carburettors. For racing or highly modified engines, EFI is often preferred for its superior control and potential for higher power output. For everyday riding and those who enjoy mechanical simplicity, carburettors retain their appeal.
• There's also a philosophical element, with some riders lamenting the "loss of classic tech" due to emissions regulations, while others defend EFI's role in making motorcycles more efficient and environmentally friendly.
• The complexity of modern electronics is a common theme. Some express a preference for simpler, purely mechanical systems, even if it means sacrificing some performance or efficiency benefits.

Frequently Asked Questions

Q1: Can any EFI bike be converted to a carburettor?

A1: While conversion kits exist for many popular models, it's not universally applicable. The feasibility depends on the specific bike's engine design, sensor integration, and the availability of suitable conversion parts. Some modern, highly integrated EFI systems might be prohibitively difficult or expensive to convert.

Q2: What are the main benefits of converting to a carburettor?

A2: The perceived benefits include simpler maintenance, potentially lower repair costs, easier aftermarket tuning for certain modifications, and a more traditional, mechanical riding experience.

Q3: What are the downsides of converting to a carburettor?

A3: Downsides include potential non-compliance with emissions regulations, loss of fuel efficiency, poorer performance in varying conditions (temperature, altitude), difficulty with cold starts, and the need to replace or bypass the stock fuel pump.

Q4: Will a conversion kit include everything I need?

A4: Good quality kits aim to be comprehensive, including the carburettor, intake adaptors, fuel tap, cables, and necessary hardware. However, always check the kit's contents carefully. You might also need tools and potentially some basic fabrication skills.

Q5: Is it legal to convert an EFI bike to a carburettor?

A5: This varies by region and local regulations. In many places, modifying a vehicle to bypass emissions controls is illegal. It may also affect your ability to pass mandatory roadworthiness inspections (like the MOT in the UK).

Q6: Does converting to a carburettor improve performance?

A6: It can, depending on the bike and the tuning. For some bikes and specific modifications (like free-flowing exhausts), a well-tuned carburettor might offer better peak power or a different power delivery compared to the stock EFI. However, modern EFI systems are often optimised for a broader range of performance and efficiency.

Conclusion

The decision to convert an EFI motorcycle to a carburettor is a personal one, often driven by a desire for simplicity, a specific riding feel, or perceived cost savings. While conversion kits make the process feasible for many models, it's essential to weigh the potential benefits against the loss of EFI's advantages, particularly regarding emissions, fuel efficiency, and all-condition performance. Thorough research into available kits for your specific model and a clear understanding of the implications for legality and emissions testing are paramount before embarking on this 'old-skool' modification.