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 Valve Shims - 5 pack 29.748300
PROX
$10.95Valve shim wear directly impacts your engine's valve clearance, compression, and overall performance consistency—especially under high-RPM conditions. PROX Valve Shims deliver precision-machined...09260906- SKU:
- 09260906
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- OUTSIDE DIAMETER METRIC:
- 7.48 MM
- RIDING STYLE:
- STREET
- RIDING STYLE:
- UTV
- VALVE SHIM THICKNESS METRIC:
- 3.00 MM
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
$10.95 -
PROX Piston Kit 01.6324.C
PROX
$166.95A worn or damaged piston can compromise your engine's compression, efficiency, and reliability—especially under high-performance conditions. The PROX Piston Kit 01.6324.C delivers OEM-equivalent...09101165- SKU:
- 09101165
- Availability:
- Ships Same Business Day
- Weight:
- 0.66 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
- BORE SIZE METRIC:
- 66.36 MM
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 66.36 MM
- PRODUCT NAME:
- PISTON KIT
$166.95 -
PROX Piston Kit 01.3341.B
PROX
$188.95A worn or damaged piston compromises compression, power delivery, and engine reliability—especially under high-performance conditions. The PROX Piston Kit 01.3341.B restores your engine to OEM...09104540- SKU:
- 09104540
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
- BORE SIZE METRIC:
- 76.97 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 76.97 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$188.95 -
PROX Piston Kit 01.6226.D
PROX
$143.95A piston failure or wear means catastrophic engine damage and costly downtime. The PROX Piston Kit 01.6226.D restores your engine to OEM specifications with precision-engineered components that...09104549- SKU:
- 09104549
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 53.97 MM
- BORE SIZE METRIC:
- 53.97 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
$143.95 -
PROX Piston Kit 01.1232.B
PROX
$177.95Worn or damaged pistons rob your engine of compression, power, and reliability. The PROX Piston Kit 01.1232.B delivers OEM-equivalent performance with precision engineering that restores your engine...09103252- SKU:
- 09103252
- Availability:
- Ships Same Business Day
- Weight:
- 0.30 LBS
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 65.98 MM
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 65.98 MM
$177.95 -
PROX Crank Bearing and Seal Kit 23.CBS13006
PROX
$116.95A crankshaft rebuild demands precision—substandard bearings and seals invite catastrophic failure and lost performance. This PROX kit eliminates guesswork by delivering OEM-spec components engineered...09240299- SKU:
- 09240299
- Availability:
- Ships Same Business Day
- Weight:
- 1.05 LBS
- PRODUCT NAME:
- BEARING AND SEAL KIT
- APPLICATION:
- CRANKSHAFT
- TYPE:
- BALL
- STYLE:
- 4-STROKE
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
$116.95 -
PROX Crank Bearing and Seal Kit 23.CBS13087
PROX
$70.95A crank bearing and seal failure can sideline your engine—and your race season. This PROX kit eliminates guesswork by delivering factory-precise replacements engineered to exact OEM specifications,...09240301- SKU:
- 09240301
- Availability:
- Ships Same Business Day
- Weight:
- 1.65 LBS
- APPLICATION:
- CRANKSHAFT
- TYPE:
- BALL
- PRODUCT NAME:
- BEARING AND SEAL KIT
- RIDING STYLE:
- ATV
- STYLE:
- 2-STROKE
- UNITS:
- KIT
$70.95 -
PROX Connecting Rod Kit - Honda CRF450R 03.1417
PROX
$183.95A connecting rod is the critical link between your crankshaft and piston—when it fails, your engine fails. The PROX Connecting Rod Kit for Honda CRF450R delivers the strength and precision needed for...09230460- SKU:
- 09230460
- Availability:
- Ships Same Business Day
- Weight:
- 1.50 LBS
- PRODUCT NAME:
- CONNECTING ROD KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
$183.95 -
PROX Connecting Rod Kit - Honda CRF150R 03.1227
PROX
$131.95A worn or damaged connecting rod compromises power delivery and risks catastrophic engine failure. The PROX Connecting Rod Kit for Honda CRF150R delivers OEM-quality reliability with...09230237- SKU:
- 09230237
- Availability:
- Ships Same Business Day
- Weight:
- 0.74 LBS
- ENGINE TYPE:
- 2-STROKE
- MATERIAL:
- FORGED
- MATERIAL:
- STEEL
- PRODUCT NAME:
- CONNECTING ROD KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
$131.95 -
PROX Connecting Rod Kit 03.1660
PROX
$197.95A connecting rod kit is fundamental to engine reliability and power delivery—it's the critical link between your crankshaft and piston, transferring combustion forces with precision. The PROX 03.1660...09230241- SKU:
- 09230241
- Availability:
- Ships Same Business Day
- Weight:
- 2.27 LBS
- ENGINE TYPE:
- 4-STROKE
- MATERIAL:
- FORGED STEEL
- PRODUCT NAME:
- CONNECTING ROD KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$197.95 -
PROX Connecting Rod Kit 03.4409
PROX
$183.95A connecting rod kit is the critical link between your engine's piston and crankshaft—any flex, wear, or imbalance directly compromises power delivery and engine longevity. The PROX 03.4409 kit...09230245- SKU:
- 09230245
- Availability:
- Ships Same Business Day
- Weight:
- 1.63 LBS
- ENGINE TYPE:
- 4-STROKE
- MATERIAL:
- FORGED STEEL
- PRODUCT NAME:
- CONNECTING ROD KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$183.95 -
PROX Connecting Rod Kit 03.6528
PROX
$188.95A quality connecting rod kit is fundamental to engine reliability and performance, especially under high RPM and boost conditions. The PROX 03.6528 delivers a complete assembly with...09230248- SKU:
- 09230248
- Availability:
- Ships Same Business Day
- Weight:
- 1.79 LBS
- UNITS:
- EACH
- ENGINE TYPE:
- 4-STROKE
- PRODUCT NAME:
- CONNECTING ROD KIT
- RIDING STYLE:
- OFF-ROAD
- MATERIAL:
- FORGED STEEL
$188.95 -
PROX Connecting Rod 03.1212
PROX
$132.95A connecting rod is the critical mechanical bridge between your crankshaft and piston—any wear, flex, or misalignment directly tanks engine efficiency and reliability. The PROX 03.1212 delivers...09230126- SKU:
- 09230126
- Availability:
- Ships Same Business Day
- Weight:
- 0.72 LBS
- ENGINE TYPE:
- 2-STROKE
- FEATURES:
- INCLUDES THRUST WASHERS
- MATERIAL:
- FORGED STEEL
- PRODUCT NAME:
- CONNECTING ROD KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$132.95 -
PROX Connecting Rod 03.2426
PROX
$183.95A quality connecting rod directly impacts engine reliability and power delivery—weak or worn rods risk catastrophic internal damage. The PROX Connecting Rod 03.2426 delivers precision engineering...09230183- SKU:
- 09230183
- Availability:
- Ships Same Business Day
- Weight:
- 1.51 LBS
- MATERIAL:
- FORGED STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- ENGINE TYPE:
- 4-STROKE
- PRODUCT NAME:
- CONNECTING ROD KIT
$183.95 -
On Sale
PROX Piston Kit 01.1315.A1
PROX
MSRP: $139.95Now: $119.00Was: $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
MSRP: $139.95Now: $119.00Was: $139.95 -
On Sale
PROX Piston Kit 01.2217.D
PROX
MSRP: $121.95Now: $90.00Was: $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
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Crank Seal Kit - KTM50 42.6011
PROX
MSRP: $16.95Now: $13.00Was: $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
MSRP: $16.95Now: $13.00Was: $16.95 -
On Sale
PROX Gasket Kit - Complete - Honda 34.1220
PROX
MSRP: $93.95Now: $76.00Was: $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
MSRP: $93.95Now: $76.00Was: $93.95 -
On Sale
PROX Gasket Kit - Complete - Honda 34.1322
PROX
MSRP: $105.95Now: $85.00Was: $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
MSRP: $105.95Now: $85.00Was: $105.95 -
On Sale
PROX Gasket Kit - Complete - Honda 34.1416
PROX
MSRP: $130.95Now: $106.00Was: $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
MSRP: $130.95Now: $106.00Was: $130.95
