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
-
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...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...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...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,...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...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...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...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
$88.95 -
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...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...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...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,...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...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...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...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...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
$77.95 -
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...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...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,...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...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
$166.95Qty in Cart: 0Quantity:Price:$166.95Subtotal: -
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...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:
