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 - Honda 35.1334
PROX
MSRP: $88.95Now: $72.00Was: $88.95A top-end gasket set is critical for maintaining cylinder head sealing integrity and preventing coolant and oil leakage that can compromise engine performance and reliability. PROX's 35.1334 gasket set delivers OEM-equivalent durability with precision...09345672- SKU:
- 09345672
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- UNITS:
- SET
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- GASKET SET
- TYPE:
- TOP END
MSRP: $88.95Now: $72.00Was: $88.95 -
On Sale
PROX Top End Gasket Set - Honda 35.1402
PROX
MSRP: $89.95Now: $76.00Was: $89.95A top-end gasket set is critical for maintaining compression, preventing coolant and oil seepage, and ensuring reliable performance between rebuild cycles. PROX's 35.1402 gasket set delivers OEM-equivalent durability with precision fitment, eliminating...09345677- SKU:
- 09345677
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- TOP END
- PRODUCT NAME:
- GASKET SET
- UNITS:
- SET
MSRP: $89.95Now: $76.00Was: $89.95 -
On Sale
PROX Top End Gasket Set - Yamaha 35.2122
PROX
MSRP: $25.95Now: $21.00Was: $25.95A quality top-end gasket set is non-negotiable for any engine rebuild or head service—it's your seal against oil leaks, coolant seepage, and compression loss that compromise performance and reliability. The PROX 35.2122 is engineered to OEM...09345686- SKU:
- 09345686
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- GASKET SET
- TYPE:
- TOP END
- UNITS:
- SET
MSRP: $25.95Now: $21.00Was: $25.95 -
On Sale
PROX Top End Gasket Set - Yamaha 35.2201
PROX
MSRP: $51.95Now: $42.00Was: $51.95A degraded top end gasket set compromises cylinder sealing, leading to compression loss, oil leakage, and reduced engine efficiency. The PROX 35.2201 restores OEM-spec sealing integrity with precision-engineered gaskets designed specifically for Yamaha...09345687- SKU:
- 09345687
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- TYPE:
- TOP END
- PRODUCT NAME:
- GASKET SET
- UNITS:
- SET
- RIDING STYLE:
- OFF-ROAD
MSRP: $51.95Now: $42.00Was: $51.95 -
On Sale
PROX Piston Kit 01.1414.A
PROX
MSRP: $210.95Now: $167.00Was: $210.95When your engine demands reliability under extreme conditions, OEM-spec pistons aren't optional—they're foundational. The PROX Piston Kit 01.1414.A delivers factory-engineered performance with precision machining that eliminates the guesswork of...09100607- SKU:
- 09100607
- Availability:
- Ships Same Business Day
- Weight:
- 0.81 LBS
- BORE SIZE METRIC:
- 95.96 MM
- PISTON DIAMETER METRIC:
- 95.96 MM
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
MSRP: $210.95Now: $167.00Was: $210.95 -
On Sale
PROX Piston Kit 01.1338.B
PROX
MSRP: $188.95Now: $158.00Was: $188.95Worn or damaged pistons compromise engine efficiency, power delivery, and long-term reliability—especially under racing conditions or high-mileage operation. The PROX Piston Kit 01.1338.B restores your engine to OEM specification with...09101127- SKU:
- 09101127
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 77.98 MM
- BORE SIZE METRIC:
- 77.98 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
MSRP: $188.95Now: $158.00Was: $188.95 -
On Sale
PROX Connecting Rod 03.6520
PROX
MSRP: $210.95Now: $170.00Was: $210.95A connecting rod is the critical link between your crankshaft and piston—it must handle extreme forces without flex or failure. The PROX 03.6520 is engineered to deliver the reliability and precision required for high-RPM performance, whether you're...09230138- SKU:
- 09230138
- Availability:
- Ships Same Business Day
- Weight:
- 1.92 LBS
- MATERIAL:
- FORGED STEEL
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- CONNECTING ROD KIT
- ENGINE TYPE:
- 4-STROKE
- RIDING STYLE:
- ATV
- UNITS:
- EACH
MSRP: $210.95Now: $170.00Was: $210.95 -
On Sale
PROX Connecting Rod 03.4285
PROX
MSRP: $132.95Now: $102.00Was: $132.95A connecting rod is the critical link between your crankshaft and piston—it's where combustion forces transfer into rotational power. The PROX 03.4285 delivers OEM-quality construction with pre-assembled bearings and hardware, eliminating guesswork...09230161- SKU:
- 09230161
- Availability:
- Ships Same Business Day
- Weight:
- 0.76 LBS
- MATERIAL:
- FORGED STEEL
- ENGINE TYPE:
- 2-STROKE
- PRODUCT NAME:
- CONNECTING ROD KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
MSRP: $132.95Now: $102.00Was: $132.95 -
On Sale
PROX Exhaust Valve 28.1356-1
PROX
MSRP: $30.95Now: $25.00Was: $30.95A precision exhaust valve is critical to maintaining peak combustion efficiency and engine reliability, especially in high-performance applications where tolerances matter. The PROX 28.1356-1 is engineered to OEM specifications, ensuring proper sealing...09260673- SKU:
- 09260673
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- VALVE
MSRP: $30.95Now: $25.00Was: $30.95 -
On Sale
PROX Intake Valve 28.1356-2
PROX
MSRP: $22.95Now: $17.00Was: $22.95A quality intake valve is critical to your engine's breathing efficiency and combustion reliability. The PROX 28.1356-2 is precision-manufactured to strict OEM specifications, ensuring consistent performance and longevity whether you're running a stock...09260674- SKU:
- 09260674
- Availability:
- Ships Same Business Day
- Weight:
- 0.09 LBS
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- VALVE
- UNITS:
- EACH
MSRP: $22.95Now: $17.00Was: $22.95 -
On Sale
PROX Connecting Rod 03.6323
PROX
MSRP: $132.95Now: $102.00Was: $132.95A connecting rod is the critical mechanical link between your piston and crankshaft—any weakness here directly translates to power loss, unreliable shifts, or catastrophic engine failure. The PROX 03.6323 is a complete assembly engineered for durability...09230173- SKU:
- 09230173
- Availability:
- Ships Same Business Day
- Weight:
- 0.99 LBS
- ENGINE TYPE:
- 2-STROKE
- MATERIAL:
- FORGED STEEL
- PRODUCT NAME:
- CONNECTING ROD KIT
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- STREET
- UNITS:
- EACH
MSRP: $132.95Now: $102.00Was: $132.95 -
On Sale
PROX Connecting Rod 03.3323
PROX
MSRP: $132.95Now: $102.00Was: $132.95A connecting rod is the critical link between your piston and crankshaft—any weakness here directly compromises power delivery, reliability, and engine longevity. The PROX 03.3323 is engineered for those who demand precision under load, with...09230185- SKU:
- 09230185
- Availability:
- Ships Same Business Day
- Weight:
- 1.02 LBS
- UNITS:
- EACH
- ENGINE TYPE:
- 2-STROKE
- MATERIAL:
- FORGED STEEL
- PRODUCT NAME:
- CONNECTING ROD KIT
- RIDING STYLE:
- OFF-ROAD
MSRP: $132.95Now: $102.00Was: $132.95 -
On Sale
PROX Crank Bearing and Seal Kit 23.CBS13092
PROX
MSRP: $70.95Now: $56.00Was: $70.95A complete crankshaft bearing and seal replacement isn't something you want to compromise on—worn bearings directly impact engine reliability, oil pressure stability, and longevity under load. This PROX kit eliminates the guesswork by delivering OEM-spec...09240302- SKU:
- 09240302
- Availability:
- Ships Same Business Day
- Weight:
- 1.60 LBS
- PRODUCT NAME:
- BEARING AND SEAL KIT
- STYLE:
- 2-STROKE
- APPLICATION:
- CRANKSHAFT
- TYPE:
- BALL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
MSRP: $70.95Now: $56.00Was: $70.95 -
On Sale
PROX Crank Bearing and Seal Kit 23.CBS14006
PROX
MSRP: $116.95Now: $93.00Was: $116.95A catastrophic crank bearing failure will sideline your engine—and your race season. This PROX Crank Bearing and Seal Kit delivers OEM-spec replacements for all critical bearing and seal positions, ensuring your crankshaft runs true under sustained high...09240305- SKU:
- 09240305
- Availability:
- Ships Same Business Day
- Weight:
- 1.40 LBS
- APPLICATION:
- CRANKSHAFT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- PRODUCT NAME:
- BEARING AND SEAL KIT
- STYLE:
- 4-STROKE
- TYPE:
- BALL
MSRP: $116.95Now: $93.00Was: $116.95 -
On Sale
PROX Top End Gasket Set - Yamaha 35.2423
PROX
MSRP: $67.95Now: $55.00Was: $67.95A top-end gasket set is essential maintenance for any serious Yamaha rider—it's the barrier between combustion efficiency and catastrophic leaks. Over time, factory gaskets deteriorate from thermal cycling and pressure stress, leading to compression loss...09345710- SKU:
- 09345710
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- PRODUCT NAME:
- GASKET SET
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- TOP END
- UNITS:
- SET
MSRP: $67.95Now: $55.00Was: $67.95 -
On Sale
PROX Top End Gasket Set - Suzuki 35.3341
PROX
MSRP: $72.95Now: $59.00Was: $72.95A top-end gasket set is essential for maintaining compression integrity and preventing oil leakage after high-mileage operation or performance modifications. The PROX 35.3341 delivers OEM-equivalent sealing across critical engine surfaces, ensuring...09345738- SKU:
- 09345738
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- UNITS:
- SET
- PRODUCT NAME:
- GASKET SET
- TYPE:
- TOP END
- RIDING STYLE:
- OFF-ROAD
MSRP: $72.95Now: $59.00Was: $72.95 -
On Sale
PROX Crank Bearing and Seal Kit 23.CBS22005
PROX
MSRP: $62.95Now: $51.00Was: $62.95A crankshaft rebuild demands precision bearings and seals that can withstand extreme loads and sustained RPM, and this Pro X kit delivers exactly that without compromise. Rather than sourcing individual components and risking fitment errors, this...09240313- SKU:
- 09240313
- Availability:
- Ships Same Business Day
- Weight:
- 0.95 LBS
- APPLICATION:
- CRANKSHAFT
- PRODUCT NAME:
- BEARING AND SEAL KIT
- UNITS:
- KIT
- RIDING STYLE:
- OFF-ROAD
- STYLE:
- 2-STROKE
- TYPE:
- BALL
MSRP: $62.95Now: $51.00Was: $62.95 -
On Sale
PROX Crank Bearing and Seal Kit 23.CBS24001
PROX
MSRP: $133.95Now: $107.00Was: $133.95A crankshaft rebuild demands precision components that match OEM tolerances—any compromise on bearing or seal quality directly impacts engine reliability and performance. This Pro X kit delivers all necessary bearings and seals in one package,...09240327- SKU:
- 09240327
- Availability:
- Ships Same Business Day
- Weight:
- 1.00 LBS
- STYLE:
- 4-STROKE
- TYPE:
- BALL
- APPLICATION:
- CRANKSHAFT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- PRODUCT NAME:
- BEARING SET
- RIDING STYLE:
- STREET
MSRP: $133.95Now: $107.00Was: $133.95 -
On Sale
PROX Crank Bearing and Seal Kit 23.CBS41088
PROX
MSRP: $36.95Now: $29.00Was: $36.95A failing crankshaft bearing or seal can compromise your entire engine's integrity, leading to catastrophic damage and costly downtime. This PROX kit delivers OEM-specification bearings and seals in a single package, eliminating the guesswork and...09240349- SKU:
- 09240349
- Availability:
- Ships Same Business Day
- Weight:
- 0.75 LBS
- PRODUCT NAME:
- BEARING AND SEAL KIT
- TYPE:
- BALL
- STYLE:
- 2-STROKE
- APPLICATION:
- CRANKSHAFT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
MSRP: $36.95Now: $29.00Was: $36.95 -
On Sale
PROX Valve Shim Kit 29.VSA948
PROX
MSRP: $116.95Now: $93.00Was: $116.95Valve shim wear directly impacts your engine's valve clearance, combustion efficiency, and overall reliability—especially under high-RPM conditions. The PROX Valve Shim Kit 29.VSA948 delivers precision-machined replacements that maintain exact OEM...09260941- SKU:
- 09260941
- Availability:
- Ships Same Business Day
- Weight:
- 1.14 LBS
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- PRODUCT NAME:
- SHIM KIT
- TYPE:
- VALVE
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- ATV
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- STREET
- VALVE SHIM THICKNESS METRIC:
- 1.20 MM - 3.50 MM
MSRP: $116.95Now: $93.00Was: $116.95
