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 01.4121.B
PROX
$99.95When your engine demands reliability at high RPM, OEM-equivalent pistons aren't optional—they're essential. The PROX Piston Kit 01.4121.B delivers factory-spec performance with the precision...PX4281B- SKU:
- PX4281B
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- PISTON DIAMETER METRIC:
- 48.46 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 48.46 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
$99.95 -
PROX Ring Set 02.4121
PROX
$24.95Piston ring wear directly impacts compression, blow-by, and fuel efficiency—making quality ring sets essential for maintaining peak engine performance. The PROX Ring Set 02.4121 delivers...PX4281R- SKU:
- PX4281R
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- PISTON RING
- UNITS:
- SET
$24.95Qty in Cart: 0Quantity:Price:$24.95Subtotal: -
PROX Piston Kit 01.4100.B
PROX
$79.95When your engine demands precision and reliability, OEM-quality pistons are non-negotiable. The PROX Piston Kit 01.4100.B delivers factory-spec performance with Japanese engineering and CNC...PX4290A- SKU:
- PX4290A
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- PISTON DIAMETER METRIC:
- 42.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 42.96 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
$79.95Qty in Cart: 0Quantity:Price:$79.95Subtotal: -
PROX Piston Kit 01.4216.A
PROX
$105.95When your engine's pistons wear beyond safe limits, you're looking at catastrophic failure and a complete rebuild. The PROX Piston Kit 01.4216.A restores your engine to OEM-specification performance...PX4296A- SKU:
- PX4296A
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- BORE SIZE METRIC:
- 53.95 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PISTON DIAMETER METRIC:
- 53.95 MM
- PRODUCT NAME:
- PISTON KIT
$105.95Qty in Cart: 0Quantity:Price:$105.95Subtotal: -
PROX Piston Kit 01.4216.B
PROX
$121.95A worn or damaged piston compromises combustion efficiency, reduces power output, and can lead to catastrophic engine failure. The PROX Piston Kit 01.4216.B delivers OEM-level reliability with...PX4296B- SKU:
- PX4296B
- Availability:
- Ships Same Business Day
- Weight:
- 0.38 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE B
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 53.96 MM
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 53.96 MM
- PRODUCT NAME:
- PISTON KIT
$121.95 -
PROX Piston Kit 01.4216.C
PROX
$105.95When you're rebuilding an engine or replacing worn pistons, you need a drop-in solution that matches OEM performance without compromise. The PROX Piston Kit 01.4216.C delivers exactly...PX4296C- SKU:
- PX4296C
- Availability:
- Ships Same Business Day
- Weight:
- 0.38 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 53.97 MM
- BORE SIZE METRIC:
- 53.97 MM
- PISTON SIZE METRIC:
- STANDARD SIZE C
- PRODUCT NAME:
- PISTON KIT
$105.95Qty in Cart: 0Quantity:Price:$105.95Subtotal: -
PROX Ring Set 02.4217
PROX
$24.95Maintaining proper ring seal is critical to engine efficiency, compression, and longevity. The PROX Ring Set 02.4217 delivers OEM-equivalent performance with Japanese manufacturing precision,...PX4296R- SKU:
- PX4296R
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- UNITS:
- SET
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON RING
- RIDING STYLE:
- OFF-ROAD
$24.95Qty in Cart: 0Quantity:Price:$24.95Subtotal: -
PROX Piston Kit 01.4218.A
PROX
$121.95A piston kit is the heart of your engine's combustion cycle—worn or damaged pistons directly compromise compression, power delivery, and engine longevity. The PROX Piston Kit 01.4218.A delivers...PX4299A- SKU:
- PX4299A
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
- BORE SIZE METRIC:
- 53.96 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 53.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$121.95 -
PROX Piston Kit 01.4218.C
PROX
$121.95Your engine's power delivery and longevity depend on piston quality—and factory replacements often compromise on durability or precision. The PROX Piston Kit 01.4218.C delivers OEM-equivalent...PX4299C- SKU:
- PX4299C
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 53.98 MM
- PISTON SIZE METRIC:
- STANDARD SIZE C
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 53.98 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$121.95 -
PROX Piston Kit 01.4322.B
PROX
$143.95A worn or damaged piston compromises combustion efficiency, power delivery, and engine longevity. The PROX Piston Kit 01.4322.B restores OEM-level performance with precision-engineered components...PX4308B- SKU:
- PX4308B
- Availability:
- Ships Same Business Day
- Weight:
- 0.75 LBS
- PISTON DIAMETER METRIC:
- 66.35 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 66.35 MM
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE B
- RIDING STYLE:
- OFF-ROAD
$143.95 -
PROX Piston Kit 01.4322.C
PROX
$143.95A piston kit is the heart of your engine's combustion chamber—when yours shows wear, blow-by, or loss of compression, replacement becomes non-negotiable for reliable performance. The PROX Piston Kit...PX4308C- SKU:
- PX4308C
- Availability:
- Ships Same Business Day
- Weight:
- 0.75 LBS
- PISTON DIAMETER METRIC:
- 66.36 MM
- PISTON SIZE METRIC:
- STANDARD SIZE C
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 66.36 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
$143.95 -
PROX Piston Kit 01.4285.A
PROX
$132.95When your engine's factory pistons show wear or you're rebuilding after high-mileage use, settling for inferior replacements compromises reliability and performance. The PROX Piston Kit 01.4285.A...PX4310A- SKU:
- PX4310A
- Availability:
- Ships Same Business Day
- Weight:
- 0.55 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 65.94 MM
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 65.94 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
$132.95 -
PROX Piston Kit 01.4285.B
PROX
$132.95When your engine's internals are worn or damaged, a quality piston kit is non-negotiable for restoring reliable power and compression. The PROX Piston Kit 01.4285.B delivers OEM-grade performance...PX4310B- SKU:
- PX4310B
- Availability:
- Ships Same Business Day
- Weight:
- 0.60 LBS
- PISTON DIAMETER METRIC:
- 65.95 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE B
- BORE SIZE METRIC:
- 65.95 MM
- PRODUCT NAME:
- PISTON KIT
$132.95 -
PROX Piston Kit 01.4285.C
PROX
$132.95A piston kit is fundamental to engine reliability and performance—worn or damaged pistons compromise combustion efficiency, increase blow-by, and risk catastrophic engine failure. The PROX Piston Kit...PX4310C- SKU:
- PX4310C
- Availability:
- Ships Same Business Day
- Weight:
- 0.65 LBS
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 65.96 MM
- BORE SIZE METRIC:
- 65.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
$132.95 -
PROX Ring Set 02.4285
PROX
$44.95Piston rings are the critical seal between your combustion chamber and crankcase—when they wear, you lose compression, power, and fuel efficiency. The PROX Ring Set 02.4285 delivers OEM-equivalent...PX4310R- SKU:
- PX4310R
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON RING
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- SET
$44.95Qty in Cart: 0Quantity:Price:$44.95Subtotal: -
PROX Piston Kit 01.4408.A
PROX
$185.95A worn or damaged piston can compromise engine efficiency, increase blow-by, and lead to catastrophic failure if left unaddressed. The PROX Piston Kit 01.4408.A delivers OEM-equivalent performance...PX4330A- SKU:
- PX4330A
- Availability:
- Ships Same Business Day
- Weight:
- 1.18 LBS
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 85.94 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON DIAMETER METRIC:
- 85.94 MM
- UNITS:
- EACH
$185.95Qty in Cart: 0Quantity:Price:$185.95Subtotal: -
PROX Piston Kit 01.4408.B
PROX
$185.95A worn or damaged piston kit compromises combustion efficiency, reduces power output, and risks catastrophic engine failure. The PROX Piston Kit 01.4408.B delivers OEM-equivalent performance with...PX4330B- SKU:
- PX4330B
- Availability:
- Ships Same Business Day
- Weight:
- 1.18 LBS
- PISTON DIAMETER METRIC:
- 85.95 MM
- BORE SIZE METRIC:
- 85.95 MM
- UNITS:
- EACH
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- PISTON SIZE METRIC:
- STANDARD SIZE B
- RIDING STYLE:
- OFF-ROAD
$185.95Qty in Cart: 0Quantity:Price:$185.95Subtotal: -
PROX Piston Kit 01.1315.A
PROX
$139.95A piston kit is your foundation for reliable engine performance and longevity. The PROX Piston Kit 01.1315.A delivers OEM-equivalent quality with precision engineering that ensures proper ring...PX4420A- SKU:
- PX4420A
- Availability:
- Ships Same Business Day
- Weight:
- 0.63 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 66.34 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 66.34 MM
- PRODUCT NAME:
- PISTON KIT
$139.95 -
PROX Ring Set 02.1315
PROX
$49.95Worn piston rings directly compromise combustion efficiency, oil consumption, and overall engine reliability—making a quality replacement essential for consistent performance. The PROX Ring Set 02...PX4420R- SKU:
- PX4420R
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- PRODUCT NAME:
- PISTON RING
- UNITS:
- SET
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
$49.95Qty in Cart: 0Quantity:Price:$49.95Subtotal: -
PROX Piston Kit 01.1320.A
PROX
$143.95Your engine's performance and longevity depend on pistons that can withstand extreme temperatures, pressures, and RPMs without compromise. The PROX Piston Kit 01.1320.A is engineered as a direct OEM...PX4430A- SKU:
- PX4430A
- Availability:
- Ships Same Business Day
- Weight:
- 0.63 LBS
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 66.34 MM
- PISTON DIAMETER METRIC:
- 66.34 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$143.95
