MOT Failures: Common Causes

Understanding Motorcycle MOT Failures

The MOT test is a crucial annual safety check for motorcycles over three years old in the UK. It ensures that your bike meets the minimum road safety and environmental standards. Failing an MOT can be a frustrating and costly experience, but understanding the common reasons for failure can help you prepare your motorcycle and avoid unexpected issues. This guide delves into the most frequent causes of MOT failures, offering insights and advice to help you keep your motorcycle in top condition and ensure it passes its test with ease.

Key Areas of Inspection

The MOT test covers a wide range of components on your motorcycle. While some issues are minor and easily rectified, others can be more significant and require professional attention. The primary areas inspected include:

• Lighting: Headlights, taillights, brake lights, and indicators must all be functional and correctly aimed.
• Brakes: The efficiency of both front and rear braking systems is rigorously tested.
• Tyres: Tread depth, condition, and suitability for the motorcycle are checked.
• Wheels and Suspension: These components are inspected for wear, damage, and proper functioning.
• Chassis: The frame and any structural components are checked for corrosion or damage.
• Exhaust System: This includes checking for leaks, security, and ensuring it meets noise and emission standards.
• Seat and Footrests: These must be secure and in good condition.
• Horn: The horn must be present and audible.
• Throttle: The throttle must operate smoothly and return to the idle position correctly.
• Fuel System: The fuel system must be secure and free from leaks.

Most Common MOT Failure Categories

While any of the above components can lead to an MOT failure, certain categories are far more prevalent. Let's explore these in detail:

1. Lighting and Signalling Equipment

This is arguably the most common reason for MOT failures. Even a simple blown bulb can result in a fail. The test checks for:

• Headlights: Must be present, correctly aimed (both dipped and main beam), and operate at the correct colour (white or yellow). Problems with aim are particularly common.
• Taillights: Must be fitted and function correctly.
• Brake Lights: Both front and rear brake light switches must activate the brake light.
• Indicators: All indicators must operate, flash at the correct rate, and be the correct colour (amber).

Tip: Regularly check all your lights before your MOT. Replacing bulbs is a simple and inexpensive way to avoid a fail.

2. Brakes

Brake system integrity is paramount for safety. Failures in this area can be due to:

• Brake Pad/Disc Wear: Worn brake pads or discs that are below the minimum thickness will cause a fail. Cracks or damage to discs are also a concern.
• Brake Fluid: Low brake fluid levels or contamination can indicate a leak or system issue.
• Brake Hoses: Cracks, chafing, or leaks in the brake hoses are serious defects.
• Brake Performance: The MOT test measures the braking efficiency. If the brakes do not provide sufficient stopping power, the motorcycle will fail. This can be due to a combination of the above factors.
• Handbrake/Parking Brake: While less common on motorcycles, if fitted, it must function correctly.

Tip: Inspect your brake pads and discs regularly. If you notice any sponginess in the brake lever or pedal, get your brake system checked by a professional.

3. Tyres and Wheels

Tyre condition directly impacts grip and handling. The MOT will check for:

• Tread Depth: The legal minimum tread depth for motorcycle tyres is 1mm across the central three-quarters of the tyre's width, with visible tread in a continuous band.
• Tyre Damage: Cuts, cracks, bulges, or exposed ply/cord are reasons for failure.
• Incorrect Tyre Type: Using car tyres or tyres not designed for motorcycles will result in a fail.
• Wheel Bearings: Excessive play in the wheel bearings can lead to a fail.
• Wheel Condition: Bent or damaged wheels, or wheels with insecurely fitted spokes, will also fail.

Tip: Ensure your tyres are inflated to the correct pressure and check the tread depth and condition regularly. Look for signs of aging, such as cracking in the sidewalls.

4. Suspension and Steering

Properly functioning suspension and steering are vital for control. Issues include:

• Worn Suspension Components: Damaged or excessively worn shock absorbers, springs, or fork seals can cause a fail. Leaking fork seals are a common problem.
• Loose Steering Head Bearings: Excessive play in the steering head bearings will lead to a fail.
• Damaged Forks: Bent or corroded fork stanchions can also result in a failed MOT.

Tip: Pay attention to how your motorcycle handles. If you notice excessive bouncing or instability, it might be time to have your suspension checked.

5. Exhaust System and Emissions

The exhaust system affects noise and environmental impact. Failures can occur due to:

• Exhaust Leaks: Any leaks in the exhaust system, from the manifold to the silencer, can cause a fail.
• Security: The exhaust system must be securely attached.
• Noise Levels: While not always tested, if the examiner deems the exhaust excessively noisy (e.g., due to a faulty baffle or aftermarket can), it can fail.
• Emissions: Although less stringent for older motorcycles compared to cars, excessive smoke or emissions can lead to a fail.

Tip: Ensure your exhaust is in good condition and securely fitted. If you have an aftermarket exhaust, make sure it complies with legal noise and emission standards.

6. Chassis and Structure

The motorcycle's frame and structural integrity are crucial for safety.

• Corrosion: Excessive corrosion, particularly on structural parts like the frame or subframe, can lead to a fail. This is more common on older bikes or those not well-maintained.
• Damage: Cracks or significant damage to the frame or mounting points will result in a fail.
• Seat Security: The rider's seat must be securely fastened.
• Footrests: Passenger footrests must be present and secure if the motorcycle is designed for two people.

Tip: Keep your motorcycle clean and check for any signs of rust or damage, especially after winter storage.

7. Other Common Issues

Beyond the major categories, several smaller issues can also lead to an MOT failure:

• Horn: Must be present and working.
• Throttle: Must operate smoothly and self-close.
• Number Plate: Must be correctly displayed, illuminated, and legible.
• Mirrors: Must be present, securely fitted, and provide a clear view.
• Chain and Sprockets: While not a direct failure point unless excessively worn or damaged, a very loose or worn chain can be a safety concern.

Preparing for Your MOT

The best way to ensure your motorcycle passes its MOT is through regular maintenance and pre-emptive checks. Here’s a checklist:

• Lights: Check all bulbs, including brake lights activated by both levers/pedals.
• Tyres: Inspect tread depth, look for damage, and check pressure.
• Brakes: Check pad thickness and look for any leaks or damage to hoses.
• Fluids: Ensure brake fluid and oil levels are correct.
• Horn: Test it.
• Chain: Check for correct tension and condition.
• General Condition: Look for any obvious signs of damage or excessive corrosion.

What Happens If You Fail?

If your motorcycle fails its MOT, you will be given a Vehicle Inspection Report (VIR) detailing the reasons for failure. You can continue to ride your motorcycle if it has a valid MOT certificate and the issues are not so severe as to make it dangerous to drive. However, it is illegal to ride a motorcycle that is deemed dangerous to drive. You will need to have the necessary repairs carried out and then present the motorcycle for a partial re-test. Depending on the nature of the failure, you may not need to pay for a full re-test.

Table: Common MOT Failures and Checks

Frequently Asked Questions (FAQs)

Q1: Can I fail my MOT for having aftermarket parts?

A: Not necessarily, but aftermarket parts must be road legal and not compromise safety or emissions. For example, a loud aftermarket exhaust might cause a fail if it's deemed too noisy.

Q2: What is the minimum tyre tread depth for a motorcycle MOT?

A: The legal minimum is 1mm across the central three-quarters of the tyre's width.

Q3: My headlight isn't aimed correctly. Can I still pass?

A: No, incorrect headlight aim is a common reason for failure. It needs to be adjusted to meet the required standard.

Q4: What if my motorcycle is very old? Are the standards different?

A: Motorcycles over 40 years old are exempt from MOT testing, provided they have not been substantially modified. For bikes between 3 and 40 years old, the same standards generally apply.

Q5: How long does an MOT test take?

A: The test typically takes around 30-45 minutes, but this can vary depending on the testing centre and the motorcycle.

Conclusion

Passing your motorcycle's MOT is a legal requirement and a vital part of ensuring your safety on the road. By understanding the common failure points and conducting regular checks, you can significantly increase your chances of a first-time pass. Regular maintenance and attention to detail are key. Don't wait until the last minute; proactive care will save you time, money, and potential hassle. Keep your motorcycle in good condition, and you'll enjoy safer, more reliable rides.

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