The Bullet Proof Designs Spark Plug / Coil Retainer is a precision-engineered solution developed specifically for Sherco 4-stroke equipped with coil-on-plug ignition systems. Because of engine vibration, chassis flex, and the coil-on-plug arrangement on Sherco engines, the ignition coil and plug lead can experience movement that may result in occasional misfire or unstable ignition under load. Over time, this movement can create intermittent spark, plug-boot separation.
To eliminate these issues, the system uses a Delrin retainer paired with a custom titanium valve cover fastener engineered to interface directly with Sherco’s three-bolt valve cover pattern. Delrin (acetal homopolymer) offers excellent dimensional stability, high fatigue resistance, and a naturally low-friction surface, making it ideal for securing the coil without damaging the lead or insulation. The included titanium bolt provides superior tensile strength while reducing weight and resisting corrosion in high-temperature environments.
Because Sherco engines vary slightly in wiring routing between models and years, the retainer is designed to mount to any ONE of the three valve cover bolt locations, giving the installer full flexibility to choose the position with the cleanest clearance around the frame, harness, thermostat housing, and breather routing. Once installed, the retainer creates a stable mechanical anchor point for the coil body, significantly reducing coil movement during impacts, chassis flex, or high-RPM vibration.
This design enhances ignition reliability in the demanding conditions Sherco riders face—technical climbs, heavy clutching, rapid load transitions, and continuous bike impacts common in hard enduro racing. By stabilizing the connection between the coil and spark plug, the retainer reduces misfires, plug-boot displacement, and premature lead wear.
Engineering Advantages for Sherco Riders
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Direct Sherco compatibility: Designed around Sherco’s 3-bolt valve cover architecture
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Delrin retainer: High fatigue resistance, low friction, excellent thermal stability
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Titanium fastener: High strength-to-weight ratio, perfect for hot engine environments
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Improved ignition stability: Reduces plug-boot separation and coil displacement under harsh vibration
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Flexible installation: Mounts to any of the three valve cover fastener locations
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Non-permanent: No cutting, drilling, or modification to Sherco OEM components
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Included Hardware
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(1) Delrin retainer
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(1) Precision shoulder bolt
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(1) Custom titanium valve cover fastener (replaces ONE OEM bolt)
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Installation Notes
This kit replaces one valve cover bolt.
Select the bolt location with the best access and cleanest wire clearance based on your specific Sherco model.
⚠️ Torque Spec:
8 Nm (71 in-lb) — do NOT overtighten the valve cover bolt.
Over-torquing can damage the valve cover, distort the sealing surface, or strip the threads.
