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 01.6394.A
PROX
$189.95A piston kit is the heart of your engine's combustion cycle—worn or damaged pistons directly compromise compression, power delivery, and reliability. The PROX Piston Kit 01.6394.A delivers OEM-equivalent performance with Japanese manufacturing precision,...09103257- SKU:
- 09103257
- Availability:
- Ships Same Business Day
- Weight:
- 0.75 LBS
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 71.94 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 71.94 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$189.95Qty in Cart: 0Quantity:Price:$189.95Subtotal: -
PROX Piston Kit 01.6394.B
PROX
$189.95When your engine demands reliability and precision, factory-spec performance isn't optional—it's essential. The PROX Piston Kit 01.6394.B delivers OEM-equivalent durability with CNC-machined precision, ensuring consistent combustion, optimal ring seal,...09103258- SKU:
- 09103258
- Availability:
- Ships Same Business Day
- Weight:
- 0.75 LBS
- BORE SIZE METRIC:
- 71.95 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 71.95 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
$189.95Qty in Cart: 0Quantity:Price:$189.95Subtotal: -
PROX Piston Kit 01.4413.A
PROX
$189.95Worn or damaged pistons compromise combustion efficiency, increase blow-by, and accelerate engine wear—ultimately costing you horsepower and reliability. The PROX Piston Kit 01.4413.A restores your engine to OEM performance specifications with...09103266- SKU:
- 09103266
- Availability:
- Ships Same Business Day
- Weight:
- 0.80 LBS
- PISTON DIAMETER METRIC:
- 95.97 MM
- PISTON SIZE METRIC:
- STANDARD
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 95.97 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$189.95Qty in Cart: 0Quantity:Price:$189.95Subtotal: -
PROX Piston Kit 01.4413.B
PROX
$210.95A piston kit is mission-critical for any engine rebuild or high-mileage refresh—it's the component that directly translates combustion pressure into power, so quality here impacts reliability and performance across the board. The PROX Piston Kit 01.4413...09103267- SKU:
- 09103267
- Availability:
- Ships Same Business Day
- Weight:
- 0.80 LBS
- PISTON DIAMETER METRIC:
- 95.98 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- BORE SIZE METRIC:
- 95.98 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
$210.95 -
PROX Piston Kit 01.4413.C
PROX
$189.95A piston kit is fundamental to engine longevity and performance—it directly impacts combustion efficiency, ring seal, and heat dissipation. The PROX Piston Kit 01.4413.C delivers OEM-quality engineering with Japanese manufacturing precision, ensuring...09103268- SKU:
- 09103268
- Availability:
- Ships Same Business Day
- Weight:
- 0.80 LBS
- PISTON DIAMETER METRIC:
- 95.99 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- BORE SIZE METRIC:
- 95.99 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
$189.95 -
PROX Piston Kit 01.6019.B
PROX
$77.95A piston kit is the heart of your engine's combustion cycle—and worn or damaged pistons directly rob you of compression, power, and reliability. The PROX Piston Kit 01.6019.B delivers OEM-equivalent performance with precision engineering and high-silicon...09103270- SKU:
- 09103270
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
- PISTON DIAMETER METRIC:
- 39.47 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 39.47 MM
$77.95 -
PROX Piston Kit 01.6019.C
PROX
$77.95A piston kit is critical to engine reliability and performance—worn or damaged pistons compromise compression, increase blow-by, and accelerate engine wear. The PROX Piston Kit 01.6019.C delivers OEM-equivalent quality with precision manufacturing,...09103271- SKU:
- 09103271
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 39.48 MM
- PISTON DIAMETER METRIC:
- 39.48 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD
- RIDING STYLE:
- OFF-ROAD
$77.95 -
PROX Piston Kit - 71.94 TM300 01.7302.A
PROX
$221.95When your engine has logged serious hours, piston wear directly compromises compression, fuel efficiency, and power output. The PROX Piston Kit 71.94 TM300 delivers OEM-equivalent performance with precision engineering that restores your engine to...09103287- SKU:
- 09103287
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 71.94 MM
- ENGINE TYPE:
- 2-STROKE
- SKIRT COATING:
- MOLY COATED
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
$221.95 -
PROX Piston Kit 01.2414.B
PROX
$179.95When you're rebuilding an engine, piston quality directly impacts reliability, longevity, and performance. The PROX Piston Kit 01.2414.B delivers OEM-equivalent engineering with Japanese manufacturing precision, ensuring your rebuild meets or exceeds...09103421- SKU:
- 09103421
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
- ENGINE TYPE:
- 4-STROKE
- PISTON DIAMETER METRIC:
- 76.96 MM
- UNITS:
- EACH
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 76.96 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
$179.95Qty in Cart: 0Quantity:Price:$179.95Subtotal: -
PROX Piston Kit 01.2444.A
PROX
$195.95When your engine demands peak performance and reliability, OEM-quality pistons are non-negotiable. The PROX Piston Kit 01.2444.A delivers factory-spec durability with precision engineering, ensuring consistent combustion efficiency and extended engine...09103423- SKU:
- 09103423
- Availability:
- Ships Same Business Day
- Weight:
- 0.85 LBS
- ENGINE TYPE:
- 4-STROKE
- PISTON DIAMETER METRIC:
- 96.95 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 96.95 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
$195.95Qty in Cart: 0Quantity:Price:$195.95Subtotal: -
PROX Piston Kit 01.2444.B
PROX
$195.95A worn or damaged piston compromises combustion efficiency, reliability, and overall engine performance. The PROX Piston Kit 01.2444.B delivers OEM-equivalent performance with precision engineering, ensuring your engine runs at peak efficiency whether...09103424- SKU:
- 09103424
- Availability:
- Ships Same Business Day
- Weight:
- 0.85 LBS
- BORE SIZE METRIC:
- 96.96 MM
- PISTON SIZE METRIC:
- STANDARD
- ENGINE TYPE:
- 4-STROKE
- PISTON DIAMETER METRIC:
- 96.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
$195.95Qty in Cart: 0Quantity:Price:$195.95Subtotal: -
PROX Piston Kit 01.4124.A
PROX
$99.95A worn or damaged piston is a silent killer of engine performance and reliability. The PROX Piston Kit 01.4124.A restores your engine to OEM specifications with precision-engineered components that handle sustained high-RPM operation without compromise...09103429- SKU:
- 09103429
- Availability:
- Ships Same Business Day
- Weight:
- 0.30 LBS
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 48.45 MM
- PISTON DIAMETER METRIC:
- 48.45 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$99.95 -
PROX Piston Kit 01.4124.B
PROX
$99.95When your engine's original pistons show signs of wear, ring blow-by, or loss of compression, a quality replacement kit is essential to restore reliability and performance. The PROX Piston Kit 01.4124.B delivers OEM-equivalent performance with...09103430- SKU:
- 09103430
- Availability:
- Ships Same Business Day
- Weight:
- 0.30 LBS
- PISTON DIAMETER METRIC:
- 48.46 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 48.46 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$99.95 -
PROX Piston Kit 01.4124.C
PROX
$99.95A piston kit is the heart of your engine's combustion cycle—worn or damaged pistons directly compromise compression, power delivery, and reliability. The PROX Piston Kit 01.4124.C delivers OEM-equivalent performance through precision Japanese...09103431- SKU:
- 09103431
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- PISTON DIAMETER METRIC:
- 48.47 MM
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 48.47 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE METRIC:
- STANDARD
- UNITS:
- EACH
$99.95 -
PROX Piston Kit - Beta RR300 01.7393.A
PROX
$199.95When your Beta RR300 demands peak performance, compromised pistons will cost you both power and reliability. This PROX piston kit delivers OEM-grade precision and durability with CNC-machined tolerances that ensure consistent combustion and minimal...09103447- SKU:
- 09103447
- Availability:
- Ships Same Business Day
- Weight:
- 0.80 LBS
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- KIT
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- SKIRT COATING:
- MOLY COATED
- ENGINE TYPE:
- 2-STROKE
- PISTON DIAMETER METRIC:
- 71.94 MM
$199.95 -
PROX Piston Kit 01.6029.B
PROX
$77.95When your engine demands precision and reliability, OEM-specification pistons are non-negotiable. The PROX Piston Kit 01.6029.B delivers factory-grade performance with the durability required for both street and competition applications, engineered to...09102483- SKU:
- 09102483
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- BORE SIZE METRIC:
- 44.97 MM
- PISTON SIZE METRIC:
- STANDARD
- PISTON DIAMETER METRIC:
- 44.97 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
$77.95 -
PROX Piston Kit 01.6029.C
PROX
$77.95A piston kit is the heart of your engine's combustion cycle—when it fails or wears, you lose compression, power, and reliability. The PROX Piston Kit 01.6029.C delivers OEM-quality replacement pistons engineered to restore your engine to factory...09102484- SKU:
- 09102484
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- PISTON DIAMETER METRIC:
- 44.98 MM
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 44.98 MM
- PISTON SIZE METRIC:
- STANDARD
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$77.95Qty in Cart: 0Quantity:Price:$77.95Subtotal: -
PROX Piston Kit 01.4345.A
PROX
$179.95Factory-spec piston performance requires precision manufacturing and material integrity—two areas where OEM replacements often fall short. The PROX Piston Kit 01.4345.A delivers exact OEM dimensions and durability through high-silicon aluminum...09103904- SKU:
- 09103904
- Availability:
- Ships Same Business Day
- Weight:
- 0.45 LBS
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 76.96 MM
- PISTON DIAMETER METRIC:
- 76.96 MM
- RIDING STYLE:
- OFF-ROAD
$179.95Qty in Cart: 0Quantity:Price:$179.95Subtotal: -
PROX Piston Kit 01.4345.B
PROX
$179.95When your engine demands reliability under extreme combustion pressures, OEM-equivalent pistons are non-negotiable. The PROX Piston Kit 01.4345.B delivers the precision and durability of factory-spec components without the factory price tag. Whether...09103905- SKU:
- 09103905
- Availability:
- Ships Same Business Day
- Weight:
- 0.45 LBS
- PISTON DIAMETER METRIC:
- 76.97 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 76.97 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
$179.95Qty in Cart: 0Quantity:Price:$179.95Subtotal: -
PROX Piston Kit 01.4345.C
PROX
$179.95A piston kit is fundamental to engine reliability and performance—it directly impacts compression, combustion efficiency, and overall durability under load. The PROX Piston Kit 01.4345.C delivers OEM-equivalent quality with precision manufacturing,...09103906- SKU:
- 09103906
- Availability:
- Ships Same Business Day
- Weight:
- 0.45 LBS
- BORE SIZE METRIC:
- 76.98 MM
- PISTON SIZE METRIC:
- STANDARD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 76.98 MM
- RIDING STYLE:
- OFF-ROAD
$179.95
