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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On Sale
PROX Ring Set 02.2314
PROX
MSRP: $49.95Now: $42.00Was: $49.95Piston ring sets are critical to engine longevity and performance—they seal combustion pressure, regulate oil consumption, and maintain compression consistency across the entire powerband. The PROX...PX7080R- SKU:
- PX7080R
- Availability:
- Ships Same Business Day
- Weight:
- 0.04 LBS
- UNITS:
- SET
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON RING
- RIDING STYLE:
- OFF-ROAD
MSRP: $49.95Now: $42.00Was: $49.95Qty in Cart: 0Quantity:Price:MSRP: $49.95Now: $42.00Was: $49.95Subtotal: -
On Sale
PROX Piston Kit 01.2321.A
PROX
MSRP: $132.95Now: $110.00Was: $132.95Factory piston performance demands precision engineering and material integrity—two hallmarks of the PROX Piston Kit 01.2321.A. Whether you're rebuilding after high-mileage wear or seeking the...PX7130A- SKU:
- PX7130A
- Availability:
- Ships Same Business Day
- Weight:
- 0.69 LBS
- ENGINE TYPE:
- 4-STROKE
- PISTON DIAMETER METRIC:
- 66.35 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 66.35 MM
MSRP: $132.95Now: $110.00Was: $132.95 -
On Sale
PROX Piston Kit 01.2321.B
PROX
MSRP: $132.95Now: $110.00Was: $132.95Worn or damaged pistons compromise engine efficiency, power delivery, and reliability—especially under high-load conditions. The PROX Piston Kit 01.2321.B restores your engine to OEM performance...PX7130B- SKU:
- PX7130B
- Availability:
- Ships Same Business Day
- Weight:
- 0.69 LBS
- BORE SIZE METRIC:
- 66.36 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 66.36 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
MSRP: $132.95Now: $110.00Was: $132.95Qty in Cart: 0Quantity:Price:MSRP: $132.95Now: $110.00Was: $132.95Subtotal: -
On Sale
PROX Piston Kit 01.2321.C
PROX
MSRP: $132.95Now: $110.00Was: $132.95Worn or damaged pistons compromise compression, fuel efficiency, and engine reliability—often requiring a complete teardown to address. The PROX Piston Kit 01.2321.C delivers OEM-equivalent...PX7130C- SKU:
- PX7130C
- Availability:
- Ships Same Business Day
- Weight:
- 0.65 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 66.37 MM
- BORE SIZE METRIC:
- 66.37 MM
- PRODUCT NAME:
- PISTON KIT
MSRP: $132.95Now: $110.00Was: $132.95 -
On Sale
PROX Piston Kit 01.2321.D
PROX
MSRP: $132.95Now: $110.00Was: $132.95A worn or damaged piston compromises combustion efficiency, reduces power output, and accelerates engine wear. The PROX Piston Kit 01.2321.D restores OEM performance specifications with...PX7130D- SKU:
- PX7130D
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- BORE SIZE METRIC:
- 66.38 MM
- PISTON DIAMETER METRIC:
- 66.38 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE D
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PRODUCT NAME:
- PISTON KIT
MSRP: $132.95Now: $110.00Was: $132.95Qty in Cart: 0Quantity:Price:MSRP: $132.95Now: $110.00Was: $132.95Subtotal: -
On Sale
PROX Piston Kit 01.2215.C
PROX
MSRP: $121.95Now: $90.00Was: $121.95A piston kit is the foundation of reliable engine performance—worn or damaged pistons compromise compression, power delivery, and longevity. The PROX Piston Kit 01.2215.C delivers OEM-equivalent...PX7214C- SKU:
- PX7214C
- Availability:
- Ships Same Business Day
- Weight:
- 0.44 LBS
- BORE SIZE METRIC:
- 53.96 MM
- ENGINE TYPE:
- 2-STROKE
- PRODUCT NAME:
- PISTON KIT
- PISTON SIZE METRIC:
- +0.02 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 53.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.2217.A
PROX
MSRP: $121.95Now: $90.00Was: $121.95Worn or damaged pistons compromise engine compression, throttle response, and fuel efficiency—leaving you stranded or forced into costly rebuilds. The PROX Piston Kit 01.2217.A restores your engine...PX7215A- SKU:
- PX7215A
- Availability:
- Ships Same Business Day
- Weight:
- 0.44 LBS
- ENGINE TYPE:
- 2-STROKE
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 53.95 MM
- PISTON DIAMETER METRIC:
- 53.95 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.2217.B
PROX
MSRP: $121.95Now: $90.00Was: $121.95If you're rebuilding an engine or restoring performance after high-mileage wear, piston quality directly impacts reliability, compression consistency, and longevity under load. The PROX Piston Kit 01...PX7215B- SKU:
- PX7215B
- Availability:
- Ships Same Business Day
- Weight:
- 0.44 LBS
- PISTON DIAMETER METRIC:
- 53.96 MM
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 53.96 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON SIZE METRIC:
- +0.01 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.2217.C
PROX
MSRP: $105.95Now: $90.00Was: $105.95When your engine demands precision engineering and proven reliability, OEM-equivalent performance becomes non-negotiable. The PROX Piston Kit 01.2217.C delivers the exact specifications your engine...PX7215C- SKU:
- PX7215C
- Availability:
- Ships Same Business Day
- Weight:
- 0.44 LBS
- ENGINE TYPE:
- 2-STROKE
- PISTON SIZE METRIC:
- +0.02 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 53.97 MM
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 53.97 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
MSRP: $105.95Now: $90.00Was: $105.95Qty in Cart: 0Quantity:Price:MSRP: $105.95Now: $90.00Was: $105.95Subtotal: -
On Sale
PROX PRO-X Crank Seal Kit 42.2102
PROX
MSRP: $10.95Now: $8.00Was: $10.95A compromised crank seal allows oil seepage that degrades engine performance and can lead to catastrophic failure if left unaddressed. The PROX PRO-X Crank Seal Kit 42.2102 delivers OEM-quality seals...094280- SKU:
- 094280
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
MSRP: $10.95Now: $8.00Was: $10.95 -
On Sale
PROX PRO-X Crank Seal Kit 42.2319
PROX
MSRP: $22.95Now: $17.00Was: $22.95A worn or leaking crankshaft seal can compromise engine integrity and lead to costly oil loss and contamination. The PROX PRO-X Crank Seal Kit 42.2319 delivers OEM-quality seals engineered to restore...094288- SKU:
- 094288
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
MSRP: $22.95Now: $17.00Was: $22.95 -
On Sale
PROX PRO-X Crank Seal Kit 42.2321
PROX
MSRP: $22.95Now: $17.00Was: $22.95A worn crank seal compromises engine integrity and invites oil leakage that compounds over time. This complete kit eliminates guesswork during crank rebuilds, delivering OEM-specification seals...094289- SKU:
- 094289
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
MSRP: $22.95Now: $17.00Was: $22.95Qty in Cart: 0Quantity:Price:MSRP: $22.95Now: $17.00Was: $22.95Subtotal: -
On Sale
PROX PRO-X Crank Seal Kit 42.2221
PROX
MSRP: $22.95Now: $17.00Was: $22.95A compromised crank seal can silently undermine your engine's reliability, causing oil weeping, contamination, and catastrophic failure if left unaddressed. The PROX PRO-X Crank Seal Kit 42.2221...094290- SKU:
- 094290
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
MSRP: $22.95Now: $17.00Was: $22.95 -
On Sale
PROX PRO-X Crank Seal Kit 42.3316
PROX
MSRP: $29.95Now: $25.00Was: $29.95A compromised crank seal is an invisible threat to engine reliability—leaking oil where it shouldn't, contaminating your combustion chamber, and accelerating wear on critical components. The PROX...094395- SKU:
- 094395
- Availability:
- Ships Same Business Day
- Weight:
- 0.06 LBS
MSRP: $29.95Now: $25.00Was: $29.95Qty in Cart: 0Quantity:Price:MSRP: $29.95Now: $25.00Was: $29.95Subtotal: -
On Sale
PROX PRO-X Crank Seal Kit 42.3219
PROX
MSRP: $25.95Now: $21.00Was: $25.95A worn or leaking crankshaft seal can undermine your engine's reliability and lead to costly oil loss and contamination. The PROX PRO-X Crank Seal Kit 42.3219 supplies all necessary seals for a...094398- SKU:
- 094398
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
MSRP: $25.95Now: $21.00Was: $25.95 -
On Sale
PROX PRO-X Crank Seal Kit 42.4105
PROX
MSRP: $10.95Now: $8.00Was: $10.95A failing crank seal compromises oil containment and invites contamination into your engine's most critical rotating assembly. This complete kit eliminates the guesswork during rebuilds by providing...094481- SKU:
- 094481
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
MSRP: $10.95Now: $8.00Was: $10.95 -
On Sale
PROX PRO-X Crank Seal Kit 42.4208
PROX
MSRP: $22.95Now: $17.00Was: $22.95A compromised crank seal is a silent killer—it allows oil to weep past critical bearing surfaces, leading to catastrophic engine failure if left unaddressed. The PROX PRO-X Crank Seal Kit 42.4208...094484- SKU:
- 094484
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
MSRP: $22.95Now: $17.00Was: $22.95 -
On Sale
PROX PRO-X Crank Seal Kit 42.4288
PROX
MSRP: $9.95Now: $8.00Was: $9.95A compromised crank seal can silently undermine engine reliability, leading to oil leaks, contamination, and catastrophic failure during critical race moments or long-term ownership. The PROX PRO-X...094487- SKU:
- 094487
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
MSRP: $9.95Now: $8.00Was: $9.95Qty in Cart: 0Quantity:Price:MSRP: $9.95Now: $8.00Was: $9.95Subtotal: -
On Sale
PROX PRO-X Crank Seal Kit 42.4300
PROX
MSRP: $30.95Now: $25.00Was: $30.95A worn or leaking crank seal compromises engine compression, increases oil consumption, and accelerates internal wear—all problems that compound quickly under racing conditions or high-mileage street...094488- SKU:
- 094488
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
MSRP: $30.95Now: $25.00Was: $30.95Qty in Cart: 0Quantity:Price:MSRP: $30.95Now: $25.00Was: $30.95Subtotal: -
On Sale
PROX PRO-X Crank Seal Kit 42.4403
PROX
MSRP: $9.95Now: $8.00Was: $9.95A failing crank seal compromises engine compression, invites oil contamination, and accelerates wear on critical internal components. This complete kit delivers OEM-quality seals engineered to...094489- SKU:
- 094489
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
MSRP: $9.95Now: $8.00Was: $9.95
