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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PROX Ring Set 02.4312
PROX
$39.95Piston rings are fundamental to engine performance—they seal combustion pressure, regulate oil consumption, and maintain compression integrity. The PROX Ring Set 02.4312 delivers OEM-grade...PX4308R- SKU:
- PX4308R
- Availability:
- Ships Same Business Day
- Weight:
- 0.04 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- SET
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- PISTON RING
$39.95Qty in Cart: 0Quantity:Price:$39.95Subtotal: -
PROX Piston Kit 01.1315.A1
PROX
$139.95Whether you're rebuilding after race-induced wear or restoring your engine to factory performance, the PROX Piston Kit 01.1315.A1 delivers the precision and durability that competitive engines demand...PX4420B- SKU:
- PX4420B
- Availability:
- Ships Same Business Day
- Weight:
- 0.63 LBS
- PISTON DIAMETER METRIC:
- 66.35 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 66.35 MM
- PRODUCT NAME:
- PISTON KIT
$139.95Qty in Cart: 0Quantity:Price:$139.95Subtotal: -
PROX Piston Kit 01.1315.A2
PROX
$139.95A piston kit is the heart of engine reliability—worn or damaged pistons compromise combustion efficiency, increase blowby, and accelerate engine degradation. The PROX Piston Kit 01.1315.A2 restores...PX4420C- SKU:
- PX4420C
- Availability:
- Ships Same Business Day
- Weight:
- 0.63 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- BORE SIZE METRIC:
- 66.36 MM
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PISTON DIAMETER METRIC:
- 66.36 MM
- PRODUCT NAME:
- PISTON KIT
$139.95Qty in Cart: 0Quantity:Price:$139.95Subtotal: -
PROX Piston Kit 01.1315.A3
PROX
$139.95When your engine is running at the limit, piston failure isn't an option. The PROX Piston Kit 01.1315.A3 delivers OEM-equivalent reliability with the precision engineering required for...PX4420D- SKU:
- PX4420D
- Availability:
- Ships Same Business Day
- Weight:
- 0.63 LBS
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PISTON DIAMETER METRIC:
- 66.37 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- BORE SIZE METRIC:
- 66.37 MM
- PRODUCT NAME:
- PISTON KIT
$139.95Qty in Cart: 0Quantity:Price:$139.95Subtotal: -
PROX Piston Kit 01.1320.A3
PROX
$139.95When your engine demands reliability under extreme conditions, OEM-specification pistons are non-negotiable. The PROX Piston Kit 01.1320.A3 delivers the precision engineering and material integrity...PX4430D- SKU:
- PX4430D
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 66.37 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 66.37 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$139.95Qty in Cart: 0Quantity:Price:$139.95Subtotal: -
PROX Piston Kit 01.3310.D
PROX
$129.95When your engine's pistons wear beyond their limits, you're looking at catastrophic performance loss and potential internal damage. The PROX Piston Kit 01.3310.D delivers OEM-equivalent reliability...PX5070D- SKU:
- PX5070D
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- PISTON DIAMETER METRIC:
- 66.96 MM
- PISTON SIZE METRIC:
- STANDARD SIZE D
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 66.96 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$129.95Qty in Cart: 0Quantity:Price:$129.95Subtotal: -
PROX Piston Kit 01.3310.E
PROX
$129.95When your engine's internals are worn or damaged, OEM-quality replacement pistons are essential for restoring compression, reliability, and performance. The PROX Piston Kit 01.3310.E delivers...PX5070E- SKU:
- PX5070E
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- PISTON DIAMETER METRIC:
- 66.97 MM
- PISTON SIZE METRIC:
- STANDARD SIZE E
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 66.97 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$129.95Qty in Cart: 0Quantity:Price:$129.95Subtotal: -
PROX Piston Kit 01.2217.D
PROX
$121.95Worn or damaged pistons compromise engine efficiency, power delivery, and reliability—making a quality replacement essential for any serious build or rebuild. The PROX Piston Kit 01.2217.D delivers...PX7215D- SKU:
- PX7215D
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- RIDING STYLE:
- OFF-ROAD
- ENGINE TYPE:
- 2-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 53.98 MM
- PISTON DIAMETER METRIC:
- 53.98 MM
- PISTON SIZE METRIC:
- STANDARD
$121.95 -
PROX PRO-X Crank Seal Kit 42.2218
PROX
$19.95A worn crankshaft seal kit compromises engine integrity and invites oil leakage that damages surrounding components and reduces performance. The PROX PRO-X Crank Seal Kit 42.2218 delivers OEM-quality...094286- SKU:
- 094286
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
$19.95Qty in Cart: 0Quantity:Price:$19.95Subtotal: -
PROX PRO-X Crank Seal Kit 42.2318
PROX
$14.95A compromised crank seal is a silent killer—allowing oil to weep into combustion chambers and destroying the precision you've built your engine around. The PROX PRO-X Crank Seal Kit 42.2318 delivers...094287- SKU:
- 094287
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
$14.95Qty in Cart: 0Quantity:Price:$14.95Subtotal: -
PROX Crank Seal Kit - KTM50 42.6011
PROX
$16.95A worn crank seal kit is the silent killer of small-displacement performance. If you're rebuilding a KTM50 or experiencing oil weeping around the crankshaft, this OEM-quality seal kit eliminates...09350605- SKU:
- 09350605
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- TYPE:
- OIL
- PRODUCT NAME:
- SEAL
- APPLICATION:
- CRANKSHAFT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
$16.95 -
PROX Crank Seal Kit - RMZ250 42.3340
PROX
$24.95A compromised crank seal kit is one of the fastest ways to tank engine reliability and performance. This PROX kit delivers OEM-quality seals engineered to eliminate leakage, preserve oil pressure,...09350460- SKU:
- 09350460
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- PRODUCT NAME:
- SEAL
- TYPE:
- OIL
- APPLICATION:
- CRANKSHAFT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
$24.95Qty in Cart: 0Quantity:Price:$24.95Subtotal: -
PROX Gasket Kit - Complete - Honda 34.1218
PROX
$89.95A complete gasket kit is essential for any engine rebuild or major service, as failing gaskets lead to fluid leaks, compression loss, and potential engine damage. The PROX Gasket Kit – Complete for...09345519- SKU:
- 09345519
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- ENGINE TYPE:
- 2-STROKE
- PRODUCT NAME:
- GASKET KIT
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- COMPLETE
- UNITS:
- KIT
$89.95Qty in Cart: 0Quantity:Price:$89.95Subtotal: -
PROX Gasket Kit - Complete - Honda 34.1220
PROX
$93.95A complete gasket kit is essential for any engine rebuild or head gasket replacement—it eliminates the risk of mixing incompatible components and ensures every sealing surface meets OEM...09345520- SKU:
- 09345520
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- COMPLETE
- UNITS:
- KIT
- PRODUCT NAME:
- GASKET KIT
$93.95Qty in Cart: 0Quantity:Price:$93.95Subtotal: -
PROX Gasket Kit - Complete - Honda 34.1224
PROX
$104.95A complete gasket kit is essential for any engine rebuild or top-end service—it ensures a proper seal across all critical engine surfaces and prevents oil and coolant leaks that compromise...09345522- SKU:
- 09345522
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
- PRODUCT NAME:
- GASKET KIT
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- COMPLETE
- UNITS:
- KIT
$104.95Qty in Cart: 0Quantity:Price:$104.95Subtotal: -
PROX Gasket Kit - Complete - Honda 34.1322
PROX
$105.95A complete gasket kit is the foundation of a reliable engine rebuild or refresh. Over time, gaskets degrade and lose their sealing integrity, leading to oil leaks, coolant seepage, and potential...09345526- SKU:
- 09345526
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- COMPLETE
- UNITS:
- KIT
- ENGINE TYPE:
- 4-STROKE
- PRODUCT NAME:
- GASKET KIT
$105.95 -
PROX Gasket Kit - Complete - Honda 34.1334
PROX
$184.95A complete gasket kit is essential for any engine rebuild or overhaul—preventing oil seepage, coolant leaks, and combustion chamber compromise that can undermine all your performance work. The PROX...09345529- SKU:
- 09345529
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- ENGINE TYPE:
- 4-STROKE
- PRODUCT NAME:
- GASKET KIT
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- COMPLETE
- UNITS:
- KIT
$184.95Qty in Cart: 0Quantity:Price:$184.95Subtotal: -
PROX Gasket Kit - Complete - Honda 34.1416
PROX
$130.95A complete gasket kit is essential for any Honda engine rebuild or overhaul—it ensures a proper seal across all critical engine surfaces and eliminates the risk of oil leaks or compression loss that...09345535- SKU:
- 09345535
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- ENGINE TYPE:
- 4-STROKE
- PRODUCT NAME:
- GASKET KIT
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- COMPLETE
- UNITS:
- KIT
$130.95 -
PROX Gasket Kit - Complete - Suzuki 34.3122
PROX
$74.95Engine gasket failure can compromise your entire build, leading to oil leaks, coolant seepage, and catastrophic performance loss. The PROX Complete Gasket Kit eliminates guesswork by providing...09345569- SKU:
- 09345569
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- PRODUCT NAME:
- GASKET KIT
- UNITS:
- KIT
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- COMPLETE
$74.95Qty in Cart: 0Quantity:Price:$74.95Subtotal: -
PROX Gasket Kit - Complete - Kawasaki 34.4027
PROX
$63.15A complete gasket kit is essential for any engine rebuild or major service on your Kawasaki—engine sealing integrity directly impacts compression, reliability, and performance. Rather than sourcing...09345588- SKU:
- 09345588
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- COMPLETE
- PRODUCT NAME:
- GASKET KIT
- UNITS:
- KIT
$63.15Qty in Cart: 0Quantity:Price:$63.15Subtotal:
