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 01.4415.C
PROX
$189.95A worn or damaged piston directly compromises engine compression, power delivery, and longevity—requiring immediate replacement to restore factory performance and reliability. The PROX Piston Kit 01.4415.C delivers OEM-equivalent precision engineering at...09103909- SKU:
- 09103909
- Availability:
- Ships Same Business Day
- Weight:
- 0.85 LBS
- PISTON DIAMETER METRIC:
- 95.99 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 95.99 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
$189.95Qty in Cart: 0Quantity:Price:$189.95Subtotal: -
PROX Piston Kit 01.2412.B
PROX
$179.95When your engine demands reliability at high RPM, factory pistons often can't deliver the precision fit and durability required for sustained performance. The PROX Piston Kit 01.2412.B is engineered to OEM specifications using high-silicon-content...09102733- SKU:
- 09102733
- Availability:
- Ships Same Business Day
- Weight:
- 0.55 LBS
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 76.96 MM
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 76.96 MM
- RIDING STYLE:
- OFF-ROAD
$179.95Qty in Cart: 0Quantity:Price:$179.95Subtotal: -
PROX Piston - SuperJet 700 01.2510.100
PROX
$129.95The PROX Piston for SuperJet 700 delivers the reliability and precision your watercraft demands during high-performance operation. A quality piston is critical to maintaining compression, power delivery, and engine longevity—especially in demanding...09102740- SKU:
- 09102740
- Availability:
- Ships Same Business Day
- Weight:
- 1.00 LBS
- ENGINE TYPE:
- 2-STROKE
- BORE SIZE METRIC:
- 82.00 MM
- PISTON MATERIAL:
- ALUMINUM
- UNITS:
- EACH
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- WATERCRAFT
$129.95 -
PROX Piston Kit - 300EXC TPI '18-'19 01.6388.C
PROX
$189.95When your 300EXC TPI demands peak performance, a worn or damaged piston compromises compression, throttle response, and engine reliability. The PROX Piston Kit delivers OEM-equivalent quality with precision manufacturing that restores your KTM's original...09106268- SKU:
- 09106268
- Availability:
- Ships Same Business Day
- Weight:
- 0.78 LBS
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- PRODUCT NAME:
- PISTON KIT
$189.95Qty in Cart: 0Quantity:Price:$189.95Subtotal: -
PROX Piston Kit - Beta RR300 '18-'19 01.7398.B
PROX
$221.95Your Beta RR300 demands precision engine internals that match factory specifications without compromise. This PROX piston kit is engineered in Japan with high-silicon aluminum and CNC machining to restore or upgrade your top-end performance. Whether...09106269- SKU:
- 09106269
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
$221.95 -
PROX Piston Kit - Standard - Yamaha PW50/80 01.2005.000
PROX
$79.95The PROX Piston Kit is engineered to deliver reliable performance and extended service life in demanding offroad conditions. Whether you're rebuilding a worn engine or refreshing your Yamaha PW50/80 for consistent power delivery, this OEM-quality piston...09106097- SKU:
- 09106097
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- BORE SIZE METRIC:
- 40.00 MM
- PRODUCT NAME:
- PISTON KIT
- BORE - OVERSIZE METRIC:
- STANDARD
- BORE - OVERSIZE:
- STANDARD
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
$79.95 -
PROX Piston Kit - Yamaha SJ 700 01.2510.000
PROX
$129.95Off-road riding demands pistons that withstand extreme heat, pressure, and rapid acceleration cycles—factory units often fall short under sustained performance conditions. The PROX Piston Kit delivers precision-engineered internals designed to maintain...09106099- SKU:
- 09106099
- Availability:
- Ships Same Business Day
- Weight:
- 1.05 LBS
- BORE SIZE METRIC:
- 81.00 MM
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- KIT
- RIDING STYLE:
- WATERCRAFT
$129.95 -
PROX Piston Kit - Yamaha SJ 700 01.2510.050
PROX
$138.95The PROX Piston Kit is engineered for demanding offroad conditions where stock pistons fall short on durability and heat management. Built to withstand the extreme pressures and temperatures of serious trail riding and competition, this kit delivers the...09106100- SKU:
- 09106100
- Availability:
- Ships Same Business Day
- Weight:
- 1.05 LBS
- BORE SIZE METRIC:
- 81.50 MM
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- KIT
$138.95 -
PROX Piston Kit 01.3001.000
PROX
$79.95High-performance piston kits are essential for offroad engines pushing beyond stock limits—whether you're running increased boost, higher RPMs, or extreme terrain. The PROX Piston Kit 01.3001.000 delivers the durability and precision engineering required...09106101- SKU:
- 09106101
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
- BORE - OVERSIZE:
- STANDARD
- BORE - OVERSIZE METRIC:
- STANDARD
- RIDING STYLE:
- ATV
- UNITS:
- KIT
- BORE SIZE METRIC:
- 41.00 MM
- PRODUCT NAME:
- PISTON KIT
$79.95 -
PROX Piston Kit - Standard - KTM 50SX 01.6012.A
PROX
$77.95The PROX Piston Kit is engineered to restore your KTM 50SX to factory performance specifications or serve as a critical replacement when wear compromises combustion efficiency and power delivery. A quality piston kit directly impacts throttle response,...09106102- SKU:
- 09106102
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
- BORE - OVERSIZE:
- STANDARD
- BORE - OVERSIZE METRIC:
- STANDARD
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 39.46 MM
- UNITS:
- KIT
- PRODUCT NAME:
- PISTON KIT
$77.95 -
PROX Piston Kit - Standard - KTM 50SX 01.6012.B
PROX
$77.95A quality piston kit is fundamental to maintaining peak engine performance and longevity in high-demand offroad riding. The PROX Piston Kit delivers OEM-grade reliability with precision-engineered tolerances, ensuring consistent compression and reduced...09106103- SKU:
- 09106103
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
- BORE SIZE METRIC:
- 39.47 MM
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- BORE - OVERSIZE:
- STANDARD
- BORE - OVERSIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
$77.95 -
PROX Piston Kit - Standard - KTM 65SX 01.6022.A
PROX
$77.95The PROX Piston Kit is engineered to restore your KTM 65SX to factory performance specifications or serve as a reliable replacement for high-mileage engines. Whether you're a weekend rider or a young racer pushing hard on the track, a quality piston kit...09106104- SKU:
- 09106104
- Availability:
- Ships Same Business Day
- Weight:
- 0.04 LBS
- BORE - OVERSIZE METRIC:
- STANDARD
- BORE - OVERSIZE:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- BORE SIZE METRIC:
- 44.96 MM
$77.95 -
PROX Piston Kit - Standard - KTM 65SX 01.6022.B
PROX
$77.95The PROX Piston Kit restores your KTM 65SX to OEM specifications with precision-engineered components built to handle the demands of competitive off-road riding. Whether you're rebuilding after a season of hard racing or performing preventative...09106105- SKU:
- 09106105
- Availability:
- Ships Same Business Day
- Weight:
- 0.12 LBS
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- BORE - OVERSIZE:
- STANDARD
- BORE - OVERSIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 44.97 MM
$77.95 -
PROX Piston Kit - Standard - 125SX 01.6220.A
PROX
$124.95Off-road performance demands pistons engineered for extreme conditions—high RPMs, aggressive throttle response, and sustained heat. The PROX Piston Kit delivers the reliability and precision fit your 125SX needs to maintain peak power delivery across...09106106- SKU:
- 09106106
- Availability:
- Ships Same Business Day
- Weight:
- 0.45 LBS
- BORE SIZE METRIC:
- 53.94 MM
- UNITS:
- KIT
- RIDING STYLE:
- OFF-ROAD
- BORE - OVERSIZE:
- STANDARD
- BORE - OVERSIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
$124.95 -
PROX Piston Kit - Standard - KTM 200EXC 01.6249.A
PROX
$139.95The PROX Piston Kit keeps your KTM 200EXC running at peak efficiency through the demands of aggressive off-road riding. When stock pistons wear or fail, you lose compression, power delivery, and fuel economy—this kit restores all three with precision...09106108- SKU:
- 09106108
- Availability:
- Ships Same Business Day
- Weight:
- 0.60 LBS
- BORE - OVERSIZE:
- STANDARD
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- BORE - OVERSIZE METRIC:
- STANDARD
- BORE SIZE METRIC:
- 63.94 MM
- PRODUCT NAME:
- PISTON KIT
$139.95Qty in Cart: 0Quantity:Price:$139.95Subtotal: -
PROX Piston Rings 02.1227
PROX
$49.95Piston rings are critical to engine longevity—they seal combustion pressure, manage blow-by, and transfer heat away from the piston crown. PROX Piston Rings 02.1227 deliver optimized heat transfer and sealing performance, ensuring reliable compression...09120647- SKU:
- 09120647
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- PRODUCT NAME:
- PISTON RING
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- PAIR
- PISTON MATERIAL:
- ALUMINUM ALLOY
- BORE SIZE METRIC:
- 65.97 MM - 65.99 MM
$49.95 -
PROX Piston Rings 02.1340
PROX
$49.95Piston rings are critical to engine efficiency—they seal combustion pressure, control oil consumption, and manage heat transfer from the piston to the cylinder wall. PROX Piston Rings 02.1340 deliver precision-engineered sealing with superior heat...09120648- SKU:
- 09120648
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- BORE SIZE METRIC:
- 76.77 MM - 76.79 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON RING
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- PAIR
$49.95Qty in Cart: 0Quantity:Price:$49.95Subtotal: -
PROX Piston Rings 02.3408
PROX
$49.95Piston rings are the critical seal between your combustion chamber and crankcase—poor sealing means lost compression, blow-by, and reduced power output. PROX Piston Rings 02.3408 deliver precise tolerances and optimized heat transfer to maintain...09120649- SKU:
- 09120649
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON RING
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 95.96 MM - 95.98 MM
- UNITS:
- PAIR
$49.95Qty in Cart: 0Quantity:Price:$49.95Subtotal: -
PROX Piston Rings 02.3340
PROX
$49.95Proper piston ring sealing is fundamental to engine efficiency and longevity. PROX Piston Rings 02.3340 deliver optimized heat transfer and gas sealing, which directly impacts combustion efficiency, oil consumption, and ring life. Whether you're...09120651- SKU:
- 09120651
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- BORE SIZE METRIC:
- 76.96 MM - 76.98 MM
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- PAIR
- PRODUCT NAME:
- PISTON RING
$49.95Qty in Cart: 0Quantity:Price:$49.95Subtotal: -
PROX Piston Rings 02.3337
PROX
$44.95Piston rings are critical to engine performance—they seal combustion pressure, regulate oil consumption, and manage heat transfer between the piston and cylinder wall. Worn or inferior rings cause compression loss, blow-by, and premature engine wear...09120653- SKU:
- 09120653
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- BORE SIZE METRIC:
- 76.96 MM - 76.98 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON RING
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- PAIR
$44.95
