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
-
On Sale
PROX Piston Kit 01.4108.A
PROX
MSRP: $93.95Now: $76.00Was: $93.95When your engine's internal components start to wear, piston degradation directly impacts compression, fuel efficiency, and overall power delivery. The PROX Piston Kit 01.4108.A is engineered as a direct OEM replacement, offering the precision and...PX4280A- SKU:
- PX4280A
- Availability:
- Ships Same Business Day
- Weight:
- 0.30 LBS
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 47.94 MM
- BORE SIZE METRIC:
- 47.94 MM
- RIDING STYLE:
- OFF-ROAD
MSRP: $93.95Now: $76.00Was: $93.95Qty in Cart: 0Quantity:Price:MSRP: $93.95Now: $76.00Was: $93.95Subtotal: -
On Sale
PROX Piston Kit 01.4108.C
PROX
MSRP: $89.95Now: $76.00Was: $89.95When your engine demands precision and reliability, stock pistons won't cut it. The PROX Piston Kit 01.4108.C delivers OEM-equivalent performance with the tight tolerances and material integrity your high-revving builds require. This complete kit...PX4280C- SKU:
- PX4280C
- Availability:
- Ships Same Business Day
- Weight:
- 0.30 LBS
- PISTON DIAMETER METRIC:
- 47.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- BORE SIZE METRIC:
- 47.96 MM
- PRODUCT NAME:
- PISTON KIT
MSRP: $89.95Now: $76.00Was: $89.95Qty in Cart: 0Quantity:Price:MSRP: $89.95Now: $76.00Was: $89.95Subtotal: -
On Sale
PROX Piston Kit 01.4121.A
PROX
MSRP: $99.95Now: $76.00Was: $99.95Factory pistons wear out or fail, leaving you with expensive downtime and compromised engine performance. The PROX Piston Kit 01.4121.A delivers OEM-equivalent quality at a fraction of the cost, engineered in Japan with the same exacting standards as...PX4281A- SKU:
- PX4281A
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 48.45 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 48.45 MM
- RIDING STYLE:
- OFF-ROAD
MSRP: $99.95Now: $76.00Was: $99.95 -
On Sale
PROX Piston Kit 01.4121.B
PROX
MSRP: $99.95Now: $76.00Was: $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 engineering required for competitive racing and serious street...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
MSRP: $99.95Now: $76.00Was: $99.95Qty in Cart: 0Quantity:Price:MSRP: $99.95Now: $76.00Was: $99.95Subtotal: -
On Sale
PROX Ring Set 02.4121
PROX
MSRP: $24.95Now: $21.00Was: $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 OEM-equivalent specifications with Japanese manufacturing...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
MSRP: $24.95Now: $21.00Was: $24.95 -
On Sale
PROX Piston Kit 01.4100.B
PROX
MSRP: $79.95Now: $68.00Was: $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 precision, ensuring consistent compression, thermal stability,...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
MSRP: $79.95Now: $68.00Was: $79.95Qty in Cart: 0Quantity:Price:MSRP: $79.95Now: $68.00Was: $79.95Subtotal: -
On Sale
PROX Piston Kit 01.4216.A
PROX
MSRP: $105.95Now: $90.00Was: $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 with precision-engineered components that handle the...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
MSRP: $105.95Now: $90.00Was: $105.95Qty in Cart: 0Quantity:Price:MSRP: $105.95Now: $90.00Was: $105.95Subtotal: -
On Sale
PROX Piston Kit 01.4216.B
PROX
MSRP: $121.95Now: $90.00Was: $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 precision engineering, restoring your engine to factory...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
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.4216.C
PROX
MSRP: $105.95Now: $90.00Was: $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 that—factory-spec reliability with Japanese manufacturing precision...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
MSRP: $105.95Now: $90.00Was: $105.95 -
On Sale
PROX Ring Set 02.4217
PROX
MSRP: $24.95Now: $21.00Was: $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, ensuring your engine maintains peak power output and minimal...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
MSRP: $24.95Now: $21.00Was: $24.95Qty in Cart: 0Quantity:Price:MSRP: $24.95Now: $21.00Was: $24.95Subtotal: -
On Sale
PROX Piston Kit 01.4218.A
PROX
MSRP: $121.95Now: $90.00Was: $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 OEM-equivalent performance with precision manufacturing that...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
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.4218.C
PROX
MSRP: $121.95Now: $90.00Was: $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 performance with Japanese manufacturing standards and...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
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.4322.B
PROX
MSRP: $143.95Now: $119.00Was: $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 manufactured to exacting tolerances in Japan. This...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
MSRP: $143.95Now: $119.00Was: $143.95 -
On Sale
PROX Piston Kit 01.4322.C
PROX
MSRP: $143.95Now: $119.00Was: $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 01.4322.C delivers OEM-equivalent engineering with...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
MSRP: $143.95Now: $119.00Was: $143.95 -
On Sale
PROX Piston Kit 01.4285.A
PROX
MSRP: $132.95Now: $110.00Was: $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 delivers OEM-equivalent durability with precision...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
MSRP: $132.95Now: $110.00Was: $132.95 -
On Sale
PROX Piston Kit 01.4285.B
PROX
MSRP: $132.95Now: $110.00Was: $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 without the OEM price tag, engineered to exact factory...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
MSRP: $132.95Now: $110.00Was: $132.95 -
On Sale
PROX Piston Kit 01.4285.C
PROX
MSRP: $132.95Now: $110.00Was: $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 01.4285.C delivers OEM-equivalent quality at a...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
MSRP: $132.95Now: $110.00Was: $132.95 -
On Sale
PROX Ring Set 02.4285
PROX
MSRP: $44.95Now: $38.00Was: $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 performance with Japanese manufacturing precision,...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
MSRP: $44.95Now: $38.00Was: $44.95Qty in Cart: 0Quantity:Price:MSRP: $44.95Now: $38.00Was: $44.95Subtotal: -
On Sale
PROX Piston Kit 01.4408.A
PROX
MSRP: $185.95Now: $158.00Was: $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 with precision engineering that restores your engine to...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
MSRP: $185.95Now: $158.00Was: $185.95Qty in Cart: 0Quantity:Price:MSRP: $185.95Now: $158.00Was: $185.95Subtotal: -
On Sale
PROX Piston Kit 01.4408.B
PROX
MSRP: $185.95Now: $158.00Was: $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 precision manufacturing that restores your engine to...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
MSRP: $185.95Now: $158.00Was: $185.95Qty in Cart: 0Quantity:Price:MSRP: $185.95Now: $158.00Was: $185.95Subtotal:
