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
-
PROX Valveshim - 10.00 x 2.45 - 5 pack 29.100245
PROX
$9.95Valve shims are critical wear items that directly impact your engine's valve clearance, combustion efficiency, and overall reliability. The PROX 10.00 x 2.45 shim delivers precision-engineered...09261002- SKU:
- 09261002
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- RIDING STYLE:
- OFF-ROAD
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- TYPE:
- VALVE
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 2.45 MM
$9.95Qty in Cart: 0Quantity:Price:$9.95Subtotal: -
PROX Valveshim - 10.00 x 2.50 - 5 pack 29.100250
PROX
$10.95Valve shim adjustment is critical to proper engine tuning, and worn or incorrect shims compromise performance and longevity. The PROX Valveshim 10.00 x 2.50 offers a precision-engineered alternative...09261003- SKU:
- 09261003
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- TYPE:
- VALVE
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 2.50 MM
$10.95 -
PROX Valveshim - 10.00 x 2.55 - 5 pack 29.100255
PROX
$10.95Valve shims are critical to maintaining proper valve clearance and engine performance, and worn or damaged shims can lead to costly compression loss and improper valve timing. The PROX Valveshim 10...09261004- SKU:
- 09261004
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- PRODUCT NAME:
- SHIM KIT
- TYPE:
- VALVE
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 2.55 MM
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
$10.95 -
PROX Piston Kit 01.6604.B
PROX
$229.95When your engine's original pistons show signs of wear, a quality replacement kit is essential to restore compression, reliability, and performance. The PROX Piston Kit 01.6604.B delivers...09101524- SKU:
- 09101524
- Availability:
- Ships Same Business Day
- Weight:
- 1.16 LBS
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE METRIC:
- STANDARD SIZE B
- UNITS:
- EACH
- BORE SIZE METRIC:
- 100.95 MM
- PISTON DIAMETER METRIC:
- 100.95 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
$229.95Qty in Cart: 0Quantity:Price:$229.95Subtotal: -
PROX Piston Kit 01.2409.A
PROX
$179.95A piston kit is critical to engine reliability and performance—worn or damaged pistons lead to compression loss, increased blow-by, and potential catastrophic engine failure. The PROX Piston Kit 01...09101609- SKU:
- 09101609
- Availability:
- Ships Same Business Day
- Weight:
- 0.54 LBS
- BORE SIZE METRIC:
- 76.95 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 76.95 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$179.95Qty in Cart: 0Quantity:Price:$179.95Subtotal: -
PROX Piston Kit 01.1338.A
PROX
$188.95A worn or damaged piston compromises compression, throttle response, and fuel efficiency—ultimately costing you performance and reliability. The PROX Piston Kit 01.1338.A restores your engine to OEM...09101126- SKU:
- 09101126
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
- BORE SIZE METRIC:
- 77.97 MM
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 77.97 MM
- RIDING STYLE:
- OFF-ROAD
$188.95 -
PROX Piston Kit 01.1338.C
PROX
$188.95When your engine's internals are worn or damaged, OEM-equivalent pistons are non-negotiable for reliable performance and longevity. The PROX Piston Kit 01.1338.C delivers factory-quality construction...09101128- SKU:
- 09101128
- Availability:
- Ships Same Business Day
- Weight:
- 0.51 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- ENGINE TYPE:
- 4-STROKE
- BORE SIZE METRIC:
- 77.99 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 77.99 MM
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
$188.95 -
PROX Piston Kit 01.1339.B
PROX
$185.95When your engine's pistons show wear or you're rebuilding after a high-mileage season, settling for substandard replacements risks catastrophic failure and lost performance. The PROX Piston Kit 01...09101130- SKU:
- 09101130
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- ENGINE TYPE:
- 4-STROKE
- PISTON DIAMETER METRIC:
- 77.98 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 77.98 MM
- PRODUCT NAME:
- PISTON KIT
$185.95Qty in Cart: 0Quantity:Price:$185.95Subtotal: -
PROX Piston Kit 01.2406.C
PROX
$179.95When your engine demands reliability and precision, OEM-quality pistons are non-negotiable. The PROX Piston Kit 01.2406.C delivers Japanese manufacturing standards with CNC-machined tolerances that...09101133- SKU:
- 09101133
- Availability:
- Ships Same Business Day
- Weight:
- 0.57 LBS
- PISTON DIAMETER METRIC:
- 76.97 MM
- BORE SIZE METRIC:
- 76.97 MM
- RIDING STYLE:
- OFF-ROAD
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
$179.95 -
PROX Piston Kit 01.2427.C
PROX
$185.95When your engine demands precision and reliability, compromised pistons will cost you races and credibility. The PROX Piston Kit 01.2427.C delivers OEM-equivalent performance with the tight...09101139- SKU:
- 09101139
- Availability:
- Ships Same Business Day
- Weight:
- 0.86 LBS
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 94.97 MM
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 94.97 MM
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
- UNITS:
- EACH
$185.95Qty in Cart: 0Quantity:Price:$185.95Subtotal: -
PROX Piston Kit 01.3338.A
PROX
$188.95A piston kit is the foundation of reliable engine performance—worn or inadequate pistons lead to compression loss, poor combustion, and premature engine failure. The PROX Piston Kit 01.3338.A...09101145- SKU:
- 09101145
- Availability:
- Ships Same Business Day
- Weight:
- 0.48 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- BORE SIZE METRIC:
- 76.96 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PISTON DIAMETER METRIC:
- 76.96 MM
- PRODUCT NAME:
- PISTON KIT
$188.95 -
PROX Piston Kit 01.3338.B
PROX
$179.95When your engine's pistons show wear or you're rebuilding for reliability, OEM-equivalent performance is non-negotiable. The PROX Piston Kit 01.3338.B delivers factory-specification durability...09101146- SKU:
- 09101146
- Availability:
- Ships Same Business Day
- Weight:
- 0.48 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 76.97 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- BORE SIZE METRIC:
- 76.97 MM
- PRODUCT NAME:
- PISTON KIT
$179.95Qty in Cart: 0Quantity:Price:$179.95Subtotal: -
PROX Piston Kit 01.3410.A
PROX
$189.95A piston kit is one of the most critical components in your engine's combustion chamber—it directly impacts compression ratio, thermal efficiency, and overall power output. The PROX Piston Kit 01...09101148- SKU:
- 09101148
- Availability:
- Ships Same Business Day
- Weight:
- 0.83 LBS
- BORE SIZE METRIC:
- 95.47 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 95.47 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
$189.95Qty in Cart: 0Quantity:Price:$189.95Subtotal: -
PROX Piston Kit 01.3410.B
PROX
$189.95Your engine's reliability depends on pistons that can handle sustained high RPM loads without sacrifice. The PROX Piston Kit 01.3410.B delivers OEM-equivalent performance with precision manufacturing...09101149- SKU:
- 09101149
- Availability:
- Ships Same Business Day
- Weight:
- 0.83 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE B
- UNITS:
- EACH
- BORE SIZE METRIC:
- 95.48 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 95.48 MM
- PRODUCT NAME:
- PISTON KIT
$189.95Qty in Cart: 0Quantity:Price:$189.95Subtotal: -
PROX Piston Kit 01.3410.C
PROX
$189.95When your engine demands reliability at high RPM, OEM-quality pistons are non-negotiable. The PROX Piston Kit 013410C delivers factory-specification performance with Japanese manufacturing precision,...09101150- SKU:
- 09101150
- Availability:
- Ships Same Business Day
- Weight:
- 0.82 LBS
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 95.49 MM
- PISTON DIAMETER METRIC:
- 95.49 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
- UNITS:
- EACH
$189.95Qty in Cart: 0Quantity:Price:$189.95Subtotal: -
PROX Piston Kit 01.4337.A
PROX
$179.95A piston kit is the core of your engine's combustion cycle—when it fails or wears, power delivery suffers and reliability tanks. The PROX Piston Kit 01.4337.A delivers factory-matched performance...09101153- SKU:
- 09101153
- Availability:
- Ships Same Business Day
- Weight:
- 0.55 LBS
- BORE SIZE METRIC:
- 76.96 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PISTON DIAMETER METRIC:
- 76.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
$179.95Qty in Cart: 0Quantity:Price:$179.95Subtotal: -
PROX Piston Kit 01.4337.B
PROX
$188.95When your engine demands precision and reliability, compromised pistons aren't an option. The PROX Piston Kit 01.4337.B delivers OEM-equivalent performance with the durability required for...09101154- SKU:
- 09101154
- Availability:
- Ships Same Business Day
- Weight:
- 0.55 LBS
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 76.97 MM
- PISTON DIAMETER METRIC:
- 76.97 MM
$188.95 -
PROX Piston Kit 01.4337.C
PROX
$179.95When your engine demands reliability under extreme conditions, OEM-quality pistons aren't optional—they're essential. The PROX Piston Kit 01.4337.C delivers factory-spec performance with precision...09101155- SKU:
- 09101155
- Availability:
- Ships Same Business Day
- Weight:
- 0.55 LBS
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 76.98 MM
- PISTON DIAMETER METRIC:
- 76.98 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE METRIC:
- STANDARD SIZE C
$179.95 -
PROX Piston Kit 01.4406.A
PROX
$210.95Your engine's pistons are the hardworking heart of combustion—they convert fuel into power thousands of times per minute. When OEM pistons wear, fatigue, or fail, performance drops and reliability...09101156- SKU:
- 09101156
- Availability:
- Ships Same Business Day
- Weight:
- 0.92 LBS
- BORE SIZE METRIC:
- 95.97 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 95.97 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$210.95Qty in Cart: 0Quantity:Price:$210.95Subtotal: -
PROX Piston Kit 01.4406.B
PROX
$189.95A worn or damaged piston kit compromises combustion efficiency, power delivery, and engine longevity. The PROX Piston Kit 01.4406.B restores OEM-level performance with precision-engineered components...09101157- SKU:
- 09101157
- Availability:
- Ships Same Business Day
- Weight:
- 0.91 LBS
- BORE SIZE METRIC:
- 95.98 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PISTON DIAMETER METRIC:
- 95.98 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$189.95Qty in Cart: 0Quantity:Price:$189.95Subtotal:
