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 Piston Kit 01.1323.A
PROX
MSRP: $143.95Now: $119.00Was: $143.95When your engine's pistons show signs of wear or damage, replacement isn't optional—it's essential for maintaining compression, preventing catastrophic failure, and preserving your engine's performance envelope. The PROX Piston Kit 01.1323.A delivers...PX1322A- SKU:
- PX1322A
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 66.34 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 66.34 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
MSRP: $143.95Now: $119.00Was: $143.95 -
On Sale
PROX Piston Kit 01.1323.B
PROX
MSRP: $139.95Now: $119.00Was: $139.95When your engine demands reliability under extreme conditions, OEM-spec pistons are non-negotiable. The PROX Piston Kit 01.1323.B delivers Japanese manufacturing precision and high-silicon aluminum construction that matches or exceeds factory...PX1322B- SKU:
- PX1322B
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 66.35 MM
- PISTON DIAMETER METRIC:
- 66.35 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
MSRP: $139.95Now: $119.00Was: $139.95Qty in Cart: 0Quantity:Price:MSRP: $139.95Now: $119.00Was: $139.95Subtotal: -
On Sale
PROX Piston Kit 01.2114.A
PROX
MSRP: $99.95Now: $76.00Was: $99.95Worn or damaged pistons compromise compression, reliability, and power output—making a quality replacement essential for any engine rebuild or high-mileage refresh. The PROX Piston Kit 01.2114.A delivers OEM-matched performance with the precision...PX2112A- SKU:
- PX2112A
- Availability:
- Ships Same Business Day
- Weight:
- 0.32 LBS
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 47.44 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON DIAMETER METRIC:
- 47.44 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON SIZE METRIC:
- STANDARD SIZE A
MSRP: $99.95Now: $76.00Was: $99.95 -
On Sale
PROX Piston Kit 01.2114.B
PROX
MSRP: $99.95Now: $76.00Was: $99.95Piston failure compromises engine reliability and performance—whether you're rebuilding after catastrophic wear or upgrading to factory-plus specifications. The PROX Piston Kit 01.2114.B delivers OEM-equivalent durability with precision engineering,...PX2112B- SKU:
- PX2112B
- Availability:
- Ships Same Business Day
- Weight:
- 0.32 LBS
- ENGINE TYPE:
- 2-STROKE
- PISTON DIAMETER METRIC:
- 47.45 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 47.45 MM
- RIDING STYLE:
- OFF-ROAD
MSRP: $99.95Now: $76.00Was: $99.95 -
On Sale
PROX Piston Kit 01.2224.A
PROX
MSRP: $121.95Now: $90.00Was: $121.95When your engine's stock pistons reach the end of their service life, you need a direct replacement that matches OEM specifications without compromise. The PROX Piston Kit 01.2224.A delivers the precision engineering and material quality required for...PX2222A- SKU:
- PX2222A
- Availability:
- Ships Same Business Day
- Weight:
- 0.32 LBS
- PISTON DIAMETER METRIC:
- 53.94 MM
- RIDING STYLE:
- OFF-ROAD
- ENGINE TYPE:
- 2-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 53.94 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.2224.B
PROX
MSRP: $121.95Now: $90.00Was: $121.95When your engine demands reliability and precision, OEM-quality pistons are non-negotiable. The PROX Piston Kit 01.2224.B delivers factory-spec performance without factory downtime, engineered in Japan to exact tolerances that keep your engine running at...PX2222B- SKU:
- PX2222B
- Availability:
- Ships Same Business Day
- Weight:
- 0.32 LBS
- BORE SIZE METRIC:
- 53.95 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE B
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 53.95 MM
- PRODUCT NAME:
- PISTON KIT
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Ring Set 02.2222
PROX
MSRP: $24.95Now: $21.00Was: $24.95Piston rings are critical to engine sealing and compression—worn or damaged rings lead to blow-by, oil consumption, and loss of horsepower. The PROX Ring Set 02.2222 delivers OEM-quality replacement rings engineered to restore your engine's performance...PX2222R- SKU:
- PX2222R
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 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 01.1408.000
PROX
MSRP: $185.95Now: $158.00Was: $185.95A worn or damaged piston kit compromises combustion efficiency, increases blow-by, and can lead to catastrophic engine failure. The PROX Piston Kit 01.1408.000 restores your engine to OEM performance specifications with precision-engineered components...PX4040- SKU:
- PX4040
- Availability:
- Ships Same Business Day
- Weight:
- 1.25 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD
- UNITS:
- EACH
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 89.00 MM
- PISTON DIAMETER METRIC:
- 89.00 MM
- PRODUCT NAME:
- PISTON KIT
MSRP: $185.95Now: $158.00Was: $185.95 -
On Sale
PROX Piston Kit 01.1408.025
PROX
MSRP: $185.95Now: $158.00Was: $185.95When your engine's pistons show wear, you're losing compression, efficiency, and power. The PROX Piston Kit 01.1408.025 restores your engine to OEM performance specifications with precision-engineered components manufactured to exacting tolerances in...PX4041- SKU:
- PX4041
- Availability:
- Ships Same Business Day
- Weight:
- 1.25 LBS
- PISTON DIAMETER METRIC:
- 89.25 MM
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PISTON MATERIAL:
- ALUMINUM ALLOY
- BORE SIZE METRIC:
- 89.25 MM
- PISTON SIZE IMPERIAL:
- +0.010'
- PRODUCT NAME:
- PISTON KIT
MSRP: $185.95Now: $158.00Was: $185.95Qty in Cart: 0Quantity:Price:MSRP: $185.95Now: $158.00Was: $185.95Subtotal: -
On Sale
PROX Piston Kit 01.1408.050
PROX
MSRP: $185.95Now: $158.00Was: $185.95A piston kit is fundamental to engine reliability and performance—worn or damaged pistons compromise compression, increase blow-by, and accelerate engine wear. The PROX Piston Kit 01.1408.050 delivers OEM-equivalent engineering with Japanese...PX4042- SKU:
- PX4042
- Availability:
- Ships Same Business Day
- Weight:
- 1.26 LBS
- BORE SIZE METRIC:
- 89.50 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON SIZE METRIC:
- +0.50 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 89.50 MM
MSRP: $185.95Now: $158.00Was: $185.95 -
On Sale
PROX Piston Kit 01.1408.075
PROX
MSRP: $185.95Now: $158.00Was: $185.95Your engine's heart demands precision and reliability—and the PROX Piston Kit 01.1408.075 delivers exactly that. Built to OEM specifications with Japanese manufacturing excellence, these pistons restore your engine's compression integrity and thermal...PX4043- SKU:
- PX4043
- Availability:
- Ships Same Business Day
- Weight:
- 1.30 LBS
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 89.75 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 89.75 MM
- PISTON SIZE IMPERIAL:
- +0.030'
- PRODUCT NAME:
- PISTON KIT
MSRP: $185.95Now: $158.00Was: $185.95Qty in Cart: 0Quantity:Price:MSRP: $185.95Now: $158.00Was: $185.95Subtotal: -
On Sale
PROX Piston Kit 01.1408.100
PROX
MSRP: $199.95Now: $158.00Was: $199.95Worn or damaged pistons compromise combustion efficiency, reduce power output, and risk catastrophic engine failure. The PROX Piston Kit 01.1408.100 delivers OEM-specification performance with CNC-machined precision, restoring your engine to...PX4044- SKU:
- PX4044
- Availability:
- Ships Same Business Day
- Weight:
- 1.25 LBS
- BORE SIZE METRIC:
- 90.00 MM
- PISTON DIAMETER METRIC:
- 90.00 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- +1.00 MM
- UNITS:
- EACH
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
MSRP: $199.95Now: $158.00Was: $199.95 -
On Sale
PROX Piston Kit 01.1408.125
PROX
MSRP: $185.95Now: $158.00Was: $185.95When your engine demands reliability and precision, OEM-equivalent performance is non-negotiable. The PROX Piston Kit 01.1408.125 delivers exact fitment and durability through Japanese manufacturing expertise and high-silicon aluminum construction that...PX4045- SKU:
- PX4045
- Availability:
- Ships Same Business Day
- Weight:
- 1.35 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 90.25 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON DIAMETER METRIC:
- 90.25 MM
- PISTON SIZE IMPERIAL:
- +0.050'
- RIDING STYLE:
- OFF-ROAD
MSRP: $185.95Now: $158.00Was: $185.95 -
On Sale
PROX Piston Kit 01.4221.A
PROX
MSRP: $105.95Now: $90.00Was: $105.95Engine reliability starts with precision internal components—and PROX pistons are engineered to exacting OEM standards without compromise. If you're rebuilding an engine or replacing worn internals, this kit delivers the durability and tolerances you...PX4221A- SKU:
- PX4221A
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 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: $105.95Now: $90.00Was: $105.95Qty in Cart: 0Quantity:Price:MSRP: $105.95Now: $90.00Was: $105.95Subtotal: -
On Sale
PROX Piston Kit 01.4221.B
PROX
MSRP: $105.95Now: $90.00Was: $105.95Your engine's piston kit is the foundation of reliable power delivery and longevity under load. Factory pistons wear, lose compression, and compromise performance—the PROX Piston Kit 01.4221.B restores OEM-specification durability with...PX4221B- SKU:
- PX4221B
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- PISTON DIAMETER METRIC:
- 53.97 MM
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 53.97 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON MATERIAL:
- ALUMINUM ALLOY
MSRP: $105.95Now: $90.00Was: $105.95Qty in Cart: 0Quantity:Price:MSRP: $105.95Now: $90.00Was: $105.95Subtotal: -
On Sale
PROX Ring Set 02.4106
PROX
MSRP: $24.95Now: $21.00Was: $24.95Piston rings are the critical seal between your combustion chamber and crankcase—when they wear, you lose compression, burn oil, and sacrifice power. The PROX Ring Set 02.4106 delivers OEM-quality replacement rings engineered in Japan to restore your...PX4230R- SKU:
- PX4230R
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- PISTON RING
- UNITS:
- SET
MSRP: $24.95Now: $21.00Was: $24.95Qty in Cart: 0Quantity:Price:MSRP: $24.95Now: $21.00Was: $24.95Subtotal: -
On Sale
PROX Piston Kit 01.1208.A3
PROX
MSRP: $105.95Now: $90.00Was: $105.95A worn or damaged piston kit compromises combustion efficiency, increases blow-by, and accelerates engine wear—ultimately costing you performance and reliability. The PROX Piston Kit 01.1208.A3 restores your engine to OEM specifications with...PX4240D- SKU:
- PX4240D
- Availability:
- Ships Same Business Day
- Weight:
- 0.38 LBS
- BORE SIZE METRIC:
- 53.97 MM
- PISTON DIAMETER METRIC:
- 53.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE METRIC:
- STANDARD SIZE A
- 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 01.1218.A1
PROX
MSRP: $132.95Now: $90.00Was: $132.95A piston kit is the heart of engine reliability and performance—without proper pistons, you're risking catastrophic failure under boost or high RPM. The PROX Piston Kit 01.1218.A1 delivers OEM-grade construction with precision engineering, ensuring your...PX4260A- SKU:
- PX4260A
- Availability:
- Ships Same Business Day
- Weight:
- 0.38 LBS
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 53.94 MM
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 53.94 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
MSRP: $132.95Now: $90.00Was: $132.95 -
On Sale
PROX Piston Kit 01.1218.A2
PROX
MSRP: $132.95Now: $90.00Was: $132.95A worn or damaged piston directly compromises engine efficiency, compression, and longevity—especially under sustained high-RPM operation. The PROX Piston Kit 01.1218.A2 delivers OEM-equivalent performance with precision engineering, ensuring reliable...PX4260B- SKU:
- PX4260B
- Availability:
- Ships Same Business Day
- Weight:
- 0.38 LBS
- BORE SIZE METRIC:
- 53.95 MM
- PISTON DIAMETER METRIC:
- 53.95 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
MSRP: $132.95Now: $90.00Was: $132.95 -
On Sale
PROX Piston Kit 01.1218.A4
PROX
MSRP: $132.95Now: $90.00Was: $132.95A piston kit is the backbone of engine reliability and performance—worn or damaged pistons lead to compression loss, increased blowby, and catastrophic engine failure. The PROX Piston Kit 01.1218.A4 delivers OEM-equivalent quality with precision...PX4260D- SKU:
- PX4260D
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- PISTON DIAMETER METRIC:
- 53.97 MM
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 53.97 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE A
MSRP: $132.95Now: $90.00Was: $132.95
