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 Piston Kit 01.3420.B
PROX
$185.95A piston kit is the heart of your engine's combustion cycle—worn or damaged pistons compromise compression, power delivery, and reliability. The PROX Piston Kit 01.3420.B delivers OEM-equivalent performance with the precision engineering of a Japanese...09100438- SKU:
- 09100438
- Availability:
- Ships Same Business Day
- Weight:
- 0.90 LBS
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$185.95 -
PROX Piston Kit 01.2429.A
PROX
$210.95A piston kit is the heart of reliable engine performance, and worn or damaged pistons compromise compression, power delivery, and fuel efficiency. The PROX Piston Kit 01.2429.A delivers OEM-equivalent quality with precision manufacturing, ensuring your...09100439- SKU:
- 09100439
- Availability:
- Ships Same Business Day
- Weight:
- 0.57 LBS
- BORE SIZE METRIC:
- 94.95 MM
- PISTON DIAMETER METRIC:
- 94.95 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$210.95 -
PROX Piston Kit 01.2429.B
PROX
$210.95A worn or damaged piston compromises combustion efficiency, reduces power output, and risks catastrophic engine failure. The PROX Piston Kit 01.2429.B delivers OEM-equivalent performance with precision engineering, restoring your engine to factory...09100440- SKU:
- 09100440
- Availability:
- Ships Same Business Day
- Weight:
- 0.82 LBS
- RIDING STYLE:
- OFF-ROAD
- ENGINE TYPE:
- 4-STROKE
- PISTON DIAMETER METRIC:
- 94.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE B
- UNITS:
- EACH
- BORE SIZE METRIC:
- 94.96 MM
- PRODUCT NAME:
- PISTON KIT
$210.95 -
PROX Piston Kit 01.1111.B
PROX
$93.95When your engine's pistons wear out, performance and reliability suffer—and replacement is non-negotiable. The PROX Piston Kit 01.1111.B delivers OEM-equivalent quality without the dealership markup, engineered to restore your engine's original...09100913- SKU:
- 09100913
- Availability:
- Ships Same Business Day
- Weight:
- 0.31 LBS
- BORE SIZE METRIC:
- 46.95 MM
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 46.95 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
$93.95Qty in Cart: 0Quantity:Price:$93.95Subtotal: -
PROX Piston Kit 01.1111.C
PROX
$93.95When your engine's pistons show wear or you're rebuilding after high-mileage use, OEM-equivalent replacement is non-negotiable for reliability and performance. The PROX Piston Kit 01.1111.C delivers Japanese manufacturing precision with high-silicon...09100914- SKU:
- 09100914
- Availability:
- Ships Same Business Day
- Weight:
- 0.30 LBS
- ENGINE TYPE:
- 2-STROKE
- PISTON DIAMETER METRIC:
- 46.96 MM
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- BORE SIZE METRIC:
- 46.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- PISTON SIZE METRIC:
- STANDARD
$93.95 -
PROX Piston Kit - Standard - Yamaha YZ 65 01.2018.A
PROX
$88.95The PROX Piston Kit delivers the reliability and precision your Yamaha YZ 65 demands in high-stress offroad conditions. Whether you're rebuilding after hard use or upgrading your engine package, this OEM-quality piston ensures consistent power delivery...09105694- SKU:
- 09105694
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
- BORE - OVERSIZE METRIC:
- STANDARD
- BORE SIZE METRIC:
- 43.44 MM
- BORE - OVERSIZE:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
$88.95 -
PROX Piston Kit - Standard - Yamaha YZ 65 01.2018.B
PROX
$88.95The PROX Piston Kit maintains optimal compression and reliable performance in your YZ 65, whether you're running stock power or building toward higher output. OEM pistons wear over time, causing compression loss, blow-by, and reduced throttle response—a...09105695- SKU:
- 09105695
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
- BORE - OVERSIZE:
- STANDARD
- RIDING STYLE:
- OFF-ROAD
- BORE - OVERSIZE METRIC:
- STANDARD
- UNITS:
- KIT
- BORE SIZE METRIC:
- 43.45 MM
- PRODUCT NAME:
- PISTON KIT
$88.95Qty in Cart: 0Quantity:Price:$88.95Subtotal: -
PROX Piston Kit - Standard - Yamaha YZ 65 01.2018.C
PROX
$88.95The PROX Piston Kit keeps your YZ 65 running at peak efficiency through reliable compression and precise bore tolerances. Factory pistons wear down from heat cycles and abrasive riding conditions—upgrading to PROX ensures consistent power delivery and...09105696- SKU:
- 09105696
- Availability:
- Ships Same Business Day
- Weight:
- 0.12 LBS
- BORE - OVERSIZE:
- STANDARD
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- BORE - OVERSIZE METRIC:
- STANDARD
- BORE SIZE METRIC:
- 43.46 MM
- PRODUCT NAME:
- PISTON KIT
$88.95 -
PROX Piston Kit 01.3413.A
PROX
$210.95Piston failure compromises engine reliability and performance—and substandard replacements accelerate wear across your entire drivetrain. The PROX Piston Kit 01.3413.A delivers OEM-equivalent durability with precision CNC-machining and...09102972- SKU:
- 09102972
- Availability:
- Ships Same Business Day
- Weight:
- 0.90 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 95.96 MM
- PISTON DIAMETER METRIC:
- 95.96 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
$210.95 -
PROX Piston Kit 01.1343.C
PROX
$185.95When your engine demands precision engineering and reliability you can count on, the PROX Piston Kit 01.1343.C delivers OEM-equivalent performance without compromise. Built from high-silicon aluminum alloy and CNC-machined to exacting tolerances, this...09104535- SKU:
- 09104535
- Availability:
- Ships Same Business Day
- Weight:
- 0.55 LBS
- PISTON DIAMETER METRIC:
- 76.79 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 76.79 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
$185.95Qty in Cart: 0Quantity:Price:$185.95Subtotal: -
PROX Piston Kit 01.3341.A
PROX
$188.95Piston failure compromises engine reliability and performance, leaving you stranded or facing catastrophic damage. The PROX Piston Kit 01.3341.A delivers OEM-grade quality with precision engineering, ensuring your engine maintains consistent compression...09104539- SKU:
- 09104539
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
- BORE SIZE METRIC:
- 76.96 MM
- PISTON DIAMETER METRIC:
- 76.96 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$188.95Qty in Cart: 0Quantity:Price:$188.95Subtotal: -
PROX Piston Kit 01.3341.C
PROX
$179.95A piston kit is the heart of your engine's combustion cycle—when tolerances wear or ring seal compromises performance, you're losing power and risking catastrophic failure. The PROX Piston Kit 01.3341.C delivers OEM-specification reliability with...09104541- SKU:
- 09104541
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 76.98 MM
- BORE SIZE METRIC:
- 76.98 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
$179.95Qty in Cart: 0Quantity:Price:$179.95Subtotal: -
PROX Piston Kit 01.4342.A
PROX
$188.95Your engine's heart depends on precision-engineered pistons that can handle extreme combustion pressures without compromise. The PROX Piston Kit 01.4342.A delivers OEM-equivalent performance with the manufacturing rigor of Japanese precision engineering,...09104542- SKU:
- 09104542
- Availability:
- Ships Same Business Day
- Weight:
- 0.45 LBS
- BORE SIZE METRIC:
- 76.96 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 76.96 MM
- RIDING STYLE:
- OFF-ROAD
$188.95 -
PROX Piston Kit 01.4342.B
PROX
$188.95A piston kit is critical to engine longevity and performance—worn or damaged pistons compromise compression, increase blow-by, and accelerate wear on cylinder walls. The PROX Piston Kit 01.4342.B delivers OEM-equivalent quality with CNC precision,...09104543- SKU:
- 09104543
- Availability:
- Ships Same Business Day
- Weight:
- 0.45 LBS
- BORE SIZE METRIC:
- 76.97 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 76.97 MM
- PISTON SIZE METRIC:
- STANDARD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$188.95 -
PROX Piston Kit 01.6029.D
PROX
$77.95When your engine demands reliability at the limit, OEM-equivalent pistons aren't a luxury—they're essential. The PROX Piston Kit 01.6029.D delivers the precision engineering and material integrity your rebuild requires, engineered in Japan to exact OEM...09104545- SKU:
- 09104545
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 44.99 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 44.99 MM
$77.95Qty in Cart: 0Quantity:Price:$77.95Subtotal: -
PROX Piston Kit 01.6226.A
PROX
$143.95A worn or damaged piston compromises combustion efficiency and can lead to catastrophic engine failure. The PROX Piston Kit 01.6226.A restores OEM-specification performance with precision-engineered components manufactured to exacting tolerances. This...09104546- SKU:
- 09104546
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 53.94 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 53.94 MM
$143.95 -
PROX Piston Kit 01.6226.B
PROX
$143.95When your engine demands reliability under extreme conditions, factory pistons simply won't cut it. The PROX Piston Kit 01.6226.B delivers OEM-equivalent performance with Japanese precision engineering, ensuring consistent combustion, minimal wear, and...09104547- SKU:
- 09104547
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- PISTON SIZE METRIC:
- STANDARD
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 53.95 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 53.95 MM
$143.95 -
PROX Piston Kit 01.6226.C
PROX
$124.95When your engine demands reliability at extreme RPMs, OEM-quality pistons are non-negotiable. The PROX Piston Kit 01.6226.C delivers Japanese precision engineering with a complete assembly—pistons, rings, wrist pins, and circlips—eliminating the need for...09104548- SKU:
- 09104548
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- PISTON DIAMETER METRIC:
- 53.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 53.96 MM
$124.95Qty in Cart: 0Quantity:Price:$124.95Subtotal: -
PROX Piston Kit - MX/EC250 01.7307.B
PROX
$166.95A worn or damaged piston directly compromises engine compression, power delivery, and fuel efficiency—leaving you stranded on the track or trail. The PROX Piston Kit restores your engine to OEM specifications with Japanese-manufactured precision,...09103246- SKU:
- 09103246
- Availability:
- Ships Same Business Day
- Weight:
- 0.55 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- SKIRT COATING:
- MOLY COATED
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- ENGINE TYPE:
- 2-STROKE
- PISTON DIAMETER METRIC:
- 66.34 MM
- PRODUCT NAME:
- PISTON KIT
$166.95 -
PROX Piston Kit - 71.94 EC300 01.7300.A
PROX
$199.95A properly functioning piston kit is critical to engine reliability and performance—worn or damaged pistons compromise compression, increase blowby, and accelerate engine wear. The PROX Piston Kit 71.94 EC300 is engineered as a direct OEM replacement,...09103248- SKU:
- 09103248
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- PISTON DIAMETER METRIC:
- 71.94 MM
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- ENGINE TYPE:
- 2-STROKE
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- ATV
- RIDING STYLE:
- STREET
- PISTON MATERIAL:
- ALUMINUM ALLOY
- SKIRT COATING:
- MOLY COATED
$199.95Qty in Cart: 0Quantity:Price:$199.95Subtotal:
