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 Intake Valve 28.1226-2
PROX
MSRP: $22.95Now: $17.00Was: $22.95A precision intake valve is critical to your engine's breathing efficiency and combustion reliability. The PROX 28.1226-2 delivers OEM-specification performance without compromise, ensuring consistent valve sealing and optimal airflow across your...09260667- SKU:
- 09260667
- Availability:
- Ships Same Business Day
- Weight:
- 0.09 LBS
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- VALVE
- APPLICATION:
- INTAKE
- UNITS:
- EACH
MSRP: $22.95Now: $17.00Was: $22.95 -
On Sale
PROX Intake Valve 28.1227-2
PROX
MSRP: $22.95Now: $17.00Was: $22.95Intake valve performance directly impacts combustion efficiency and engine responsiveness—compromised valve integrity leads to poor sealing, lost compression, and reduced power output. The PROX 28.1227-2 is engineered to OEM specifications, ensuring...09260669- SKU:
- 09260669
- Availability:
- Ships Same Business Day
- Weight:
- 0.06 LBS
- RIDING STYLE:
- OFF-ROAD
- MATERIAL:
- STEEL
- PRODUCT NAME:
- VALVE
- APPLICATION:
- INTAKE
- UNITS:
- EACH
MSRP: $22.95Now: $17.00Was: $22.95 -
On Sale
PROX Exhaust Valve 28.1323-1
PROX
MSRP: $30.95Now: $25.00Was: $30.95A precision exhaust valve is critical to maintaining proper engine breathing and combustion efficiency—without it, you're looking at compromised performance, increased emissions, and potential engine damage. The PROX 28.1323-1 is engineered to OEM...09260670- SKU:
- 09260670
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- VALVE
- UNITS:
- EACH
MSRP: $30.95Now: $25.00Was: $30.95 -
On Sale
PROX Intake Valve 28.1323-2
PROX
MSRP: $22.95Now: $17.00Was: $22.95The PROX Intake Valve 28.1323-2 is engineered to restore optimal valve sealing and combustion efficiency in high-demand engine applications. Precision-manufactured to OEM specifications, this valve ensures consistent performance and longevity under...09260671- SKU:
- 09260671
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- RIDING STYLE:
- OFF-ROAD
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- PRODUCT NAME:
- VALVE
- UNITS:
- EACH
MSRP: $22.95Now: $17.00Was: $22.95 -
On Sale
PROX Intake Valve 28.1381-2
PROX
MSRP: $22.95Now: $17.00Was: $22.95A properly functioning intake valve is critical to your engine's breathing efficiency and power delivery. The PROX 28.1381-2 is precision-engineered to OEM specifications, ensuring reliable sealing and consistent performance across combustion cycles...09260676- SKU:
- 09260676
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- APPLICATION:
- INTAKE
- UNITS:
- EACH
- MATERIAL:
- STEEL
- PRODUCT NAME:
- VALVE
- RIDING STYLE:
- OFF-ROAD
MSRP: $22.95Now: $17.00Was: $22.95 -
PROX Exhaust Valve 28.2200-1
PROX
$25.95A precision exhaust valve is critical to your engine's breathing efficiency and power delivery—especially in high-performance applications where stock components fall short. The PROX 28.2200-1 is engineered to OEM specifications with the tolerances and...09260678- SKU:
- 09260678
- Availability:
- Ships Same Business Day
- Weight:
- 0.06 LBS
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- VALVE
- UNITS:
- EACH
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
$25.95 -
PROX Intake Valve 28.2200-2
PROX
$17.95A precision intake valve is fundamental to your engine's breathing efficiency and combustion reliability. The PROX 28.2200-2 is manufactured to OEM specifications, ensuring consistent performance and longevity whether you're rebuilding a stock engine or...09260679- SKU:
- 09260679
- Availability:
- Ships Same Business Day
- Weight:
- 0.06 LBS
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- PRODUCT NAME:
- VALVE
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
$17.95 -
PROX Intake Valve 28.6520-2
PROX
$35.95A quality intake valve is fundamental to your engine's breathing efficiency and overall performance. The PROX 28.6520-2 is engineered to OEM specifications, ensuring reliable operation and proper sealing under all combustion cycles. Whether you're...09260689- SKU:
- 09260689
- Availability:
- Ships Same Business Day
- Weight:
- 0.12 LBS
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- PRODUCT NAME:
- VALVE
- RIDING STYLE:
- ATV
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
$35.95 -
PROX Valve and Spring Kit 28.SES2402-1
PROX
$155.95If you're running high-RPM applications or pushing your engine beyond stock parameters, OEM valve and spring assemblies become your limiting factor. The PROX 28.SES2402-1 kit replaces weak factory components with nitrided steel valves and premium chrome...09261455- SKU:
- 09261455
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- PRODUCT NAME:
- SPRING KIT
- APPLICATION:
- EXHAUST
- TYPE:
- VALVE
$155.95 -
PROX Valve and Spring Kit 28.SES3338-1
PROX
$155.95If you're running your engine hard at high RPM, stock valve springs simply don't have the strength to keep up—resulting in valve float, lost power, and potential catastrophic failure. The PROX Valve and Spring Kit 28.SES3338-1 replaces those weak OEM...09261456- SKU:
- 09261456
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- UNITS:
- KIT
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- SPRING KIT
- TYPE:
- VALVE
$155.95 -
PROX Valve and Spring Kit 28.SIS1336-2
PROX
$155.95If you're pushing your engine to the limit, factory valve springs and valves will hold you back—they're simply not engineered for sustained high-RPM loads or the thermal stress of performance driving. The PROX 28.SIS1336-2 Kit replaces those weak links...09261458- SKU:
- 09261458
- Availability:
- Ships Same Business Day
- Weight:
- 0.29 LBS
- PRODUCT NAME:
- SPRING KIT
- TYPE:
- VALVE
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
$155.95 -
PROX Valve and Spring Kit 28.SIS4335-2
PROX
$155.95If you're pushing your engine to its limits, OEM valves and springs become your limiting factor. The PROX 28.SIS4335-2 Kit replaces them with nitrided steel valves and premium chrome vanadium springs engineered to handle extreme RPMs and sustained...09261462- SKU:
- 09261462
- Availability:
- Ships Same Business Day
- Weight:
- 0.30 LBS
- TYPE:
- VALVE
- MATERIAL:
- STEEL
- APPLICATION:
- INTAKE
- PRODUCT NAME:
- SPRING KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
$155.95 -
PROX Exhaust Valve 28.1340-1
PROX
$46.95A precision exhaust valve is critical to your engine's breathing efficiency and thermal management. The PROX 28.1340-1 delivers OEM-specification reliability without compromise, ensuring consistent valve sealing and longevity under sustained performance...09261419- SKU:
- 09261419
- Availability:
- Ships Same Business Day
- Weight:
- 0.07 LBS
- MATERIAL:
- STEEL
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- VALVE
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$46.95 -
PROX Valve and Spring Kit 28.SES2440-1
PROX
$139.95If you're running your engine hard, OEM valves and springs become a liability under sustained high-RPM operation. The PROX 28.SES2440-1 kit replaces these weak points with nitrided steel valves and premium chrome vanadium springs, engineered to handle...09261427- SKU:
- 09261427
- Availability:
- Ships Same Business Day
- Weight:
- 0.24 LBS
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- SPRING KIT
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- TYPE:
- VALVE
$139.95 -
PROX Valve and Spring Kit 28.SES6327-1
PROX
$155.95OEM valve springs lose their tension under sustained high-RPM operation, leading to valve float and catastrophic engine failure. The PROX Valve and Spring Kit 28.SES6327-1 replaces those compromised components with nitrided steel valves and premium...09261429- SKU:
- 09261429
- Availability:
- Ships Same Business Day
- Weight:
- 0.26 LBS
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- SPRING KIT
- TYPE:
- VALVE
$155.95 -
PROX Valve and Spring Kit 28.SES6329-1
PROX
$155.95If you're running your engine hard, OEM valves and springs will hold you back. The PROX 28.SES6329-1 Kit replaces weak factory components with nitrided steel valves and premium chrome vanadium springs engineered to handle sustained high-RPM abuse without...09261430- SKU:
- 09261430
- Availability:
- Ships Same Business Day
- Weight:
- 0.24 LBS
- APPLICATION:
- EXHAUST
- TYPE:
- VALVE
- PRODUCT NAME:
- SPRING KIT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- MATERIAL:
- STEEL
$155.95 -
PROX Piston Kit 01.1113.B
PROX
$99.95A piston kit is critical to engine reliability and performance—worn or damaged pistons compromise compression, increase blow-by, and accelerate engine degradation. The PROX Piston Kit 01.1113.B delivers OEM-equivalent durability with precision...09100020- SKU:
- 09100020
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 47.45 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PISTON DIAMETER METRIC:
- 47.45 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$99.95 -
PROX Piston Kit 01.1113.C
PROX
$99.95Whether you're rebuilding a tired engine or replacing worn pistons, the PROX Piston Kit 01.1113.C delivers the precision and reliability that professional rebuilds demand. Engineered as a direct OEM replacement with Japanese manufacturing standards, this...09100021- SKU:
- 09100021
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- PISTON DIAMETER METRIC:
- 47.46 MM
- PISTON SIZE METRIC:
- STANDARD SIZE C
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 47.46 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PRODUCT NAME:
- PISTON KIT
$99.95 -
PROX Piston Kit 01.4022.B
PROX
$88.95When your engine demands reliability under extreme conditions, OEM-spec pistons are non-negotiable. The PROX Piston Kit 01.4022.B delivers factory-quality performance with the precision tolerances required for high-RPM stability and consistent...09100023- SKU:
- 09100023
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- BORE SIZE METRIC:
- 44.46 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 44.46 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- RIDING STYLE:
- OFF-ROAD
$88.95 -
PROX Piston Kit 01.2406.B
PROX
$188.95A worn or damaged piston compromises engine compression, efficiency, and reliability—especially under boost or sustained high RPM. The PROX Piston Kit 01.2406.B delivers OEM-equivalent performance with precision manufacturing that ensures proper ring...09100028- SKU:
- 09100028
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- BORE SIZE METRIC:
- 76.96 MM
- ENGINE TYPE:
- 4-STROKE
- PISTON DIAMETER METRIC:
- 76.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE B
- RIDING STYLE:
- OFF-ROAD
$188.95
