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...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...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...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...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...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...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...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...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...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...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...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...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...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,...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...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...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...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...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...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...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
