Dirt Bike Engine
Dirt Bike Engine Parts at JJ Motorsports
Discover a full range of dirt bike engine components for rebuilding or upgrading your performance from JJ Motorsports. From crankshafts to cylinder heads and piston kits, these precision-engineered components ensure reliable performance. For additional upgrades, check out our full selection of off-road dirt bike parts to keep your engine running at peak efficiency on the track or trails.
Shop trusted brands like Wiseco for forged piston kits and K&N for high-flow oil filters. Explore related categories such as Dirt Bike Air and Fuel for intake upgrades or Dirt Bike Exhaust for complete systems.
Browse our in-stock inventory below with same-day shipping and expert support. Questions? Contact us for fitment advice!
- Product
- Qty in Cart
- Quantity
- Price
- Subtotal
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On Sale
PROX Top End Gasket Set - Sea Doo 35.5512
PROX
MSRP: $112.68Now: $72.00Was: $112.68A leaking or worn top end gasket set compromises combustion efficiency and can lead to costly engine damage if left unaddressed. The PROX Top End Gasket Set is engineered to factory specifications, ensuring a reliable seal that restores compression and...09347145- SKU:
- 09347145
- Availability:
- Ships Same Business Day
- Weight:
- 0.36 LBS
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- SET
- PRODUCT NAME:
- GASKET SET
- TYPE:
- TOP END
MSRP: $112.68Now: $72.00Was: $112.68 -
PROX Top End Gasket Set 35.6118
PROX
$36.95A quality top-end gasket set is non-negotiable for maintaining compression and preventing oil seepage in your engine. Whether you're rebuilding after a full race season or performing preventive maintenance, the PROX 35.6118 delivers OEM-grade sealing...09347146- SKU:
- 09347146
- Availability:
- Ships Same Business Day
- Weight:
- 0.11 LBS
- UNITS:
- SET
- PRODUCT NAME:
- GASKET SET
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- TOP END
$36.95 -
PROX Top End Gasket Set 35.6315
PROX
$88.95A top-end gasket set is critical for maintaining compression integrity and preventing fluid leaks in your engine's combustion chamber. PROX's 35.6315 gasket set delivers the precision fit and material quality required for reliable performance, whether...09347148- SKU:
- 09347148
- Availability:
- Ships Same Business Day
- Weight:
- 0.16 LBS
- UNITS:
- SET
- PRODUCT NAME:
- GASKET SET
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- TOP END
$88.95 -
PROX Top End Gasket Set 35.6316
PROX
$88.95A quality top-end gasket set is critical to maintaining compression, preventing oil seepage, and ensuring reliable engine performance across countless heat cycles. The PROX 35.6316 delivers OEM-equivalent sealing with materials engineered to handle...09347149- SKU:
- 09347149
- Availability:
- Ships Same Business Day
- Weight:
- 0.21 LBS
- UNITS:
- SET
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- TOP END
- PRODUCT NAME:
- GASKET SET
$88.95 -
PROX Top End Gasket Set 35.6317
PROX
$72.95A properly sealed top end is non-negotiable for engine reliability and performance. The PROX Top End Gasket Set 35.6317 delivers OEM-equivalent sealing integrity with precision manufacturing, preventing coolant and oil leakage that can compromise your...09347150- SKU:
- 09347150
- Availability:
- Ships Same Business Day
- Weight:
- 0.11 LBS
- PRODUCT NAME:
- GASKET SET
- UNITS:
- SET
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- TOP END
$72.95 -
PROX Valve and Spring Kit 28.SIS2444-2
PROX
$166.95If you're running high-RPM applications or pushing your engine beyond stock parameters, OEM valve springs will struggle to keep pace with valve float and premature wear. The PROX Valve and Spring Kit 28.SIS2444-2 replaces both intake and exhaust valves...09262729- SKU:
- 09262729
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
- PRODUCT NAME:
- VALVE AND SPRING KIT
- UNITS:
- KIT
$166.95 -
PROX Exhaust Valve 28.1334-1
PROX
$40.95Proper valve operation is critical to engine reliability and performance—a compromised exhaust valve leads to lost compression, increased emissions, and potential catastrophic engine damage. The PROX 28.1334-1 is engineered to OEM specifications,...09260143- SKU:
- 09260143
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
- PRODUCT NAME:
- VALVE
- UNITS:
- EACH
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- APPLICATION:
- EXHAUST
$40.95 -
PROX Exhaust Valve 28.1402-1
PROX
$40.95Proper valve clearance and sealing are critical to engine performance and longevity—a worn or damaged exhaust valve directly impacts compression, combustion efficiency, and power output. The PROX Exhaust Valve 28.1402-1 is engineered to OEM...09260144- SKU:
- 09260144
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- VALVE
- UNITS:
- EACH
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
$40.95 -
PROX Exhaust Valve 28.1495-1
PROX
$35.95A precision exhaust valve is critical to maintaining proper engine breathing and combustion efficiency, directly impacting power output and engine longevity. The PROX 28.1495-1 is engineered to OEM specifications, ensuring reliable performance whether...09260145- SKU:
- 09260145
- Availability:
- Ships Same Business Day
- Weight:
- 0.12 LBS
- RIDING STYLE:
- ATV
- UNITS:
- EACH
- MATERIAL:
- STEEL
- PRODUCT NAME:
- VALVE
- RIDING STYLE:
- OFF-ROAD
- APPLICATION:
- EXHAUST
$35.95 -
PROX Exhaust Valve 28.1654-1
PROX
$56.95Exhaust valve performance directly impacts engine efficiency, combustion temperature management, and overall power delivery. The PROX 28.1654-1 is precision-engineered to OEM specifications, ensuring reliable sealing and consistent valve timing across...09260146- SKU:
- 09260146
- Availability:
- Ships Same Business Day
- Weight:
- 0.12 LBS
- RIDING STYLE:
- OFF-ROAD
- MATERIAL:
- STEEL
- PRODUCT NAME:
- VALVE
- UNITS:
- EACH
- APPLICATION:
- EXHAUST
$56.95 -
PROX Exhaust Valve 28.3402-1
PROX
$35.95A worn or damaged exhaust valve compromises engine breathing, power delivery, and fuel efficiency—forcing your engine to work harder for less performance. The PROX Exhaust Valve 28.3402-1 restores proper valve sealing and thermal management, ensuring...09260147- SKU:
- 09260147
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- ATV
- UNITS:
- EACH
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- VALVE
$35.95 -
PROX Exhaust Valve 28.2418-1
PROX
$29.95Exhaust valves are critical to engine breathing and combustion efficiency—a worn or substandard valve directly compromises horsepower, fuel economy, and engine longevity. The PROX 28.2418-1 is precision-manufactured to OEM specifications, ensuring...09260148- SKU:
- 09260148
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- VALVE
$29.95 -
PROX Intake Valve 28.1495-2
PROX
$25.95Precision valve operation is critical to engine reliability and performance—any deviation in valve geometry directly impacts combustion efficiency and durability. The PROX Intake Valve 28.1495-2 is engineered to exact OEM specifications, ensuring your...09260149- SKU:
- 09260149
- Availability:
- Ships Same Business Day
- Weight:
- 0.12 LBS
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- PRODUCT NAME:
- VALVE
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$25.95 -
PROX Intake Valve 28.1654-2
PROX
$35.95A properly functioning intake valve is critical to your engine's breathing efficiency and power delivery. The PROX 28.1654-2 is precision-manufactured to OEM specifications, ensuring reliable sealing and consistent performance under demanding conditions...09260150- SKU:
- 09260150
- Availability:
- Ships Same Business Day
- Weight:
- 0.12 LBS
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- PRODUCT NAME:
- VALVE
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$35.95 -
PROX Intake Valve 28.3402-2
PROX
$30.95A worn or damaged intake valve directly compromises cylinder sealing, fuel efficiency, and combustion reliability—issues that cascade into poor engine performance and increased wear on surrounding components. The PROX 28.3402-2 is engineered to OEM...09260151- SKU:
- 09260151
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- PRODUCT NAME:
- VALVE
- RIDING STYLE:
- ATV
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
$30.95 -
PROX Intake Valve 28.2418-3
PROX
$22.95Precision intake valve operation is critical to engine efficiency and reliability—especially under high-performance conditions where tolerances matter. The PROX 28.2418-3 is manufactured to exacting OEM specifications, ensuring consistent sealing, proper...09260153- SKU:
- 09260153
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PRODUCT NAME:
- VALVE
$22.95 -
PROX Valve Shims - 5 pack 29.748120
PROX
$10.95Valve shim wear directly impacts your engine's valve clearance and overall performance consistency—especially under high-RPM conditions where precision matters most. PROX Valve Shims deliver OEM-equivalent durability at a fraction of the cost, making...09260870- SKU:
- 09260870
- Availability:
- Ships Same Business Day
- Weight:
- 0.01 LBS
- OUTSIDE DIAMETER METRIC:
- 7.48 MM
- RIDING STYLE:
- STREET
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 1.20 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
$10.95 -
PROX Valve Shims - 5 pack 29.748135
PROX
$10.95Valve shim wear directly impacts your engine's valve clearance and overall performance—letting them degrade compromises both power delivery and engine longevity. PROX Valve Shims give you a cost-effective way to maintain precise valve lash without the...09260873- SKU:
- 09260873
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 1.35 MM
- RIDING STYLE:
- OFF-ROAD
- OUTSIDE DIAMETER METRIC:
- 7.48 MM
- RIDING STYLE:
- STREET
- RIDING STYLE:
- WATERCRAFT
- RIDING STYLE:
- ATV
- TYPE:
- VALVE
$10.95 -
PROX Valve Shims - 5 pack 29.748140
PROX
$10.95Valve shim wear directly impacts cylinder head performance and engine longevity—replacing worn shims restores proper valve clearance and prevents costly damage to valves, seats, and rocker arms. PROX Valve Shims deliver OEM-quality precision at a...09260874- SKU:
- 09260874
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- UNITS:
- 5 PACK
- OUTSIDE DIAMETER METRIC:
- 7.48 MM
- RIDING STYLE:
- ATV
- RIDING STYLE:
- STREET
- RIDING STYLE:
- WATERCRAFT
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
- VALVE SHIM THICKNESS METRIC:
- 1.40 MM
$10.95 -
PROX Valve Shims - 5 pack 29.748145
PROX
$10.95Valve shims are critical wear items that directly impact your engine's valve clearance, timing accuracy, and overall performance. Factory shims wear down over time, leading to improper valve overlap and potential power loss—these PROX replacements offer...09260875- SKU:
- 09260875
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 1.45 MM
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- UTV
- TYPE:
- VALVE
- OUTSIDE DIAMETER METRIC:
- 7.48 MM
- RIDING STYLE:
- ATV
- RIDING STYLE:
- STREET
$10.95
