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
ATHENA Cylinder Kit - RMZ450 - 100mm P400510100006
ATHENA
MSRP: $1,156.95Now: $1,041.00Was: $1,156.95The ATHENA Cylinder Kit delivers measurable gains in displacement and compression for the RMZ450, translating directly to increased horsepower and throttle response. The nickel-carbide coated aluminum cylinder and molybdenum-coated forged piston are...09310114- SKU:
- 09310114
- Availability:
- Ships Same Business Day
- Weight:
- 3.73 LBS
- PRODUCT NAME:
- CYLINDER KIT
- STYLE:
- BIG BORE
- DISPLACEMENT:
- 490 CC
- ENGINE TYPE:
- 4-STROKE
- MATERIAL:
- ALUMINUM
- CYLINDER BORE COATING:
- NICKEL-CARBIDE
- UNITS:
- KIT
- BORE SIZE METRIC:
- 100.00 MM
- RIDING STYLE:
- OFF-ROAD
MSRP: $1,156.95Now: $1,041.00Was: $1,156.95 -
On Sale
ATHENA Cylinder Kit - KX125 - 58mm P400250100011
ATHENA
MSRP: $1,201.95Now: $1,082.00Was: $1,201.95The ATHENA Cylinder Kit delivers the displacement and reliability your KX125 demands when stock limits won't cut it. With a 58mm bore, optimized water jacket design, and factory-grade coatings, you're getting race-proven engineering that bolts straight...09310109- SKU:
- 09310109
- Availability:
- Ships Same Business Day
- Weight:
- 5.62 LBS
- BORE SIZE METRIC:
- 58.00 MM
- MATERIAL:
- ALUMINUM
- CYLINDER BORE COATING:
- NICKEL-CARBIDE
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- DISPLACEMENT:
- 144 CC
- PRODUCT NAME:
- CYLINDER KIT
- STYLE:
- BIG BORE
- UNITS:
- KIT
MSRP: $1,201.95Now: $1,082.00Was: $1,201.95 -
On Sale
ATHENA Cylinder Kit - KX65 - 50mm P400250100007
ATHENA
MSRP: $932.95Now: $840.00Was: $932.95If you're pushing your KX65 to its limits, a worn or compromised cylinder is a bottleneck you can't afford. The ATHENA Cylinder Kit delivers measurable gains in compression consistency and heat dissipation, translating directly to more responsive...09310107- SKU:
- 09310107
- Availability:
- Ships Same Business Day
- Weight:
- 3.31 LBS
- PRODUCT NAME:
- CYLINDER KIT
- STYLE:
- BIG BORE
- DISPLACEMENT:
- 80 CC
- BORE SIZE METRIC:
- 50.00 MM
- CYLINDER BORE COATING:
- NICKEL-CARBIDE
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- MATERIAL:
- ALUMINUM
MSRP: $932.95Now: $840.00Was: $932.95 -
On Sale
ATHENA Cylinder Kit - YZ125 - 54mm P400485100017
ATHENA
MSRP: $1,110.95Now: $1,000.00Was: $1,110.95The ATHENA Cylinder Kit delivers the displacement and reliability your YZ125 needs to stay competitive on the track. With a larger 54mm bore and premium coatings engineered for durability, this kit provides measurable power gains while maintaining the...09310095- SKU:
- 09310095
- Availability:
- Ships Same Business Day
- Weight:
- 5.61 LBS
- DISPLACEMENT:
- 125 CC
- PRODUCT NAME:
- CYLINDER KIT
- MATERIAL:
- ALUMINUM
- BORE SIZE METRIC:
- 54.00 MM
- CYLINDER BORE COATING:
- NICKEL-CARBIDE
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- STYLE:
- STOCK BORE
MSRP: $1,110.95Now: $1,000.00Was: $1,110.95 -
On Sale
ATHENA Cylinder Kit - KLX/DRZ/KFX/LTZ400 P400510100002
ATHENA
MSRP: $1,117.95Now: $1,006.00Was: $1,117.95Stock cylinder limitations can compromise peak horsepower and throttle response on your KLX, DRZ, KFX, or LTZ400. The ATHENA Cylinder Kit delivers measurable gains through advanced materials and thermal engineering—larger water jackets keep temperatures...09310016- SKU:
- 09310016
- Availability:
- Ships Same Business Day
- Weight:
- 4.96 LBS
- DISPLACEMENT:
- 435 CC
- MATERIAL:
- ALUMINUM
- BORE SIZE METRIC:
- 94.00 MM
- ENGINE TYPE:
- 4-STROKE
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- CYLINDER BORE COATING:
- NICKEL-CARBIDE
- RIDING STYLE:
- STREET
- PRODUCT NAME:
- CYLINDER KIT
- STYLE:
- BIG BORE
- UNITS:
- KIT
MSRP: $1,117.95Now: $1,006.00Was: $1,117.95 -
On Sale
ATHENA Cylinder Kit - DRZ/KFX P400510100001
ATHENA
MSRP: $772.95Now: $696.00Was: $772.95Stock cylinder limits your engine's potential, especially if you're running higher compression or extended operating hours. The ATHENA Cylinder Kit delivers measurable gains in peak power and reliability through precision engineering and materials...09310015- SKU:
- 09310015
- Availability:
- Ships Same Business Day
- Weight:
- 4.71 LBS
- BORE SIZE METRIC:
- 90.00 MM
- MATERIAL:
- ALUMINUM
- STYLE:
- STOCK BORE
- CYLINDER BORE COATING:
- NICKEL-CARBIDE
- ENGINE TYPE:
- 4-STROKE
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- PRODUCT NAME:
- CYLINDER KIT
- DISPLACEMENT:
- 400 CC
MSRP: $772.95Now: $696.00Was: $772.95 -
On Sale
ATHENA Cylinder Kit - KX125 - 54mm P400250100001
ATHENA
MSRP: $970.95Now: $874.00Was: $970.95The ATHENA Cylinder Kit delivers the displacement and thermal management your KX125 needs to compete at the highest levels. A larger 54mm bore paired with advanced nickel-carbide coating and optimized water jackets ensures consistent performance in...09310012- SKU:
- 09310012
- Availability:
- Ships Same Business Day
- Weight:
- 6.18 LBS
- BORE SIZE METRIC:
- 54.00 MM
- CYLINDER BORE COATING:
- NICKEL-CARBIDE
- UNITS:
- KIT
- DISPLACEMENT:
- 125 CC
- PRODUCT NAME:
- CYLINDER KIT
- ENGINE TYPE:
- 2-STROKE
- MATERIAL:
- ALUMINUM
- RIDING STYLE:
- OFF-ROAD
- STYLE:
- STOCK BORE
MSRP: $970.95Now: $874.00Was: $970.95 -
Hot Cams Titanium Intake Valve for 2015 Yamaha WR250F 2014-2015 Yamaha YZ250F 8400036-2
HOT CAMS
$123.95Stock intake valves are a common failure point in high-demand 4-stroke engines, especially in competition environments where sustained RPM and heat cycles accelerate wear. The HOT CAMS Titanium Intake Valve delivers the durability and precision sealing...09262637- SKU:
- 09262637
- Availability:
- Ships Same Business Day
- Weight:
- 0.11 LBS
- APPLICATION:
- INTAKE
- PRODUCT NAME:
- VALVE
- RIDING STYLE:
- OFF-ROAD
- BASE COLOR:
- SILVER
- COLOR/FINISH:
- TITANIUM
- MATERIAL:
- NITRIDE COATED
- MATERIAL:
- TITANIUM
- UNITS:
- EACH
$123.95 -
Hot Cams Titanium Exhaust Valve Yamaha YZ250F 2014-2021 8400036-1
HOT CAMS
$110.95If you're pushing your YZ250F to the limit on the track, your stock exhaust valve won't cut it—thermal cycling and sustained RPMs demand a valve engineered for punishment. The HOT CAMS Titanium Exhaust Valve is purpose-built to handle the demands of...09262636- SKU:
- 09262636
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- APPLICATION:
- EXHAUST
- BASE COLOR:
- SILVER
- UNITS:
- EACH
- COLOR/FINISH:
- TITANIUM
- RIDING STYLE:
- OFF-ROAD
- MATERIAL:
- TITANIUM
- PRODUCT NAME:
- VALVE
$110.95 -
Hot Cams Titanium Intake Valve for Honda CRF250R 2010-2017 8400032-2
HOT CAMS
$110.95The HOT CAMS Titanium Intake Valve delivers the precision and durability your CRF250R demands, whether you're pushing lap times or maintaining peak engine efficiency. Factory valves wear under sustained performance—this forged, nitride-coated replacement...09262630- SKU:
- 09262630
- Availability:
- Ships Same Business Day
- Weight:
- 0.06 LBS
- BASE COLOR:
- SILVER
- APPLICATION:
- INTAKE
- RIDING STYLE:
- OFF-ROAD
- COLOR/FINISH:
- TITANIUM
- MATERIAL:
- NITRIDE COATED
- MATERIAL:
- TITANIUM
- UNITS:
- EACH
- PRODUCT NAME:
- VALVE
$110.95 -
Hot Cams Titanium Intake Valve for Kawasaki KX450F 2009-2015 8400031-2
HOT CAMS
$110.95The intake valve is critical to your KX450F's breathing efficiency—a worn or inferior valve directly limits peak power and throttle response. Hot Cams' forged construction and precision machining deliver the reliability of an OEM part with measurably...09262629- SKU:
- 09262629
- Availability:
- Ships Same Business Day
- Weight:
- 0.11 LBS
- BASE COLOR:
- SILVER
- APPLICATION:
- INTAKE
- RIDING STYLE:
- OFF-ROAD
- COLOR/FINISH:
- TITANIUM
- MATERIAL:
- NITRIDE COATED
- MATERIAL:
- TITANIUM
- UNITS:
- EACH
- PRODUCT NAME:
- VALVE
$110.95 -
Hot Cams Titanium Exhaust Valve Kawasaki KX450F 2009-2015 8400031-1
HOT CAMS
$123.95The stock exhaust valve on your KX450F will eventually wear, compromising combustion efficiency and overall engine performance. Hot Cams' titanium exhaust valve is engineered with forged one-piece construction and precision surface treatments to...09262628- SKU:
- 09262628
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- BASE COLOR:
- SILVER
- MATERIAL:
- NITRIDE COATED
- UNITS:
- EACH
- COLOR/FINISH:
- TITANIUM
- RIDING STYLE:
- OFF-ROAD
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- VALVE
- MATERIAL:
- TITANIUM
$123.95 -
Hot Cams Titanium Intake Valve 2009-2016 Kawasaki KX250F 8400030-2
HOT CAMS
$110.95The intake valve is critical to your KX250F's combustion efficiency and top-end reliability—worn or damaged valves directly compromise throttle response and power delivery. Hot Cams' forged construction and precision machining ensure a perfect seal every...09262627- SKU:
- 09262627
- Availability:
- Ships Same Business Day
- Weight:
- 0.11 LBS
- BASE COLOR:
- SILVER
- MATERIAL:
- NITRIDE COATED
- UNITS:
- EACH
- COLOR/FINISH:
- TITANIUM
- RIDING STYLE:
- OFF-ROAD
- APPLICATION:
- INTAKE
- MATERIAL:
- TITANIUM
- PRODUCT NAME:
- VALVE
$110.95 -
Hot Cams Titanium Intake Valve for Honda CRF450X 2005-2017 8400028-2
HOT CAMS
$86.95If you're running your CRF450X hard—whether on the track or the trail—your intake valves are working at the edge of their limits. The HOT CAMS Titanium Intake Valve replaces worn or damaged stock valves with forged precision engineering that improves...09262624- SKU:
- 09262624
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- MATERIAL:
- TITANIUM
- APPLICATION:
- INTAKE
- PRODUCT NAME:
- VALVE
- BASE COLOR:
- SILVER
- COLOR/FINISH:
- TITANIUM
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$86.95 -
Hot Cams Titanium Intake Valve for Honda CRF450R 2009-2016 8400027-2
HOT CAMS
$107.95Factory intake valves wear under high RPM and aggressive riding, compromising combustion efficiency and power delivery. The Hot Cams Titanium Intake Valve restores OEM fitment with superior materials and precision engineering, ensuring consistent valve...09262623- SKU:
- 09262623
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- MATERIAL:
- TITANIUM
- APPLICATION:
- INTAKE
- PRODUCT NAME:
- VALVE
- COLOR/FINISH:
- TITANIUM
- MATERIAL:
- NITRIDE COATED
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- BASE COLOR:
- SILVER
$107.95 -
Hot Cams Titanium Intake Valve 2004-2008 Kawasaki KX250F 8400011-2
HOT CAMS
$110.95If you're running a 2004-2008 Kawasaki KX250F, valve integrity directly impacts throttle response, fuel efficiency, and overall engine reliability. The HOT CAMS Titanium Intake Valve 8400011-2 is engineered as a precision OEM replacement that restores—or...09262612- SKU:
- 09262612
- Availability:
- Ships Same Business Day
- Weight:
- 0.03 LBS
- MATERIAL:
- NITRIDE COATED
- PRODUCT NAME:
- VALVE
- UNITS:
- EACH
- COLOR/FINISH:
- TITANIUM
- MATERIAL:
- TITANIUM
- APPLICATION:
- INTAKE
- BASE COLOR:
- SILVER
- RIDING STYLE:
- OFF-ROAD
$110.95 -
Hot Cams Titanium Exhaust Valve 2004-2016 Kawasaki KX250F 8400011-1
HOT CAMS
$110.95The stock exhaust valve on your KX250F endures extreme thermal cycling and combustion pressures lap after lap. Hot Cams' titanium exhaust valve replaces worn or damaged OEM components with a forged, precision-engineered alternative that delivers better...09262611- SKU:
- 09262611
- Availability:
- Ships Same Business Day
- Weight:
- 0.06 LBS
- APPLICATION:
- EXHAUST
- BASE COLOR:
- SILVER
- MATERIAL:
- NITRIDE COATED
- UNITS:
- EACH
- COLOR/FINISH:
- TITANIUM
- PRODUCT NAME:
- VALVE
- RIDING STYLE:
- OFF-ROAD
- MATERIAL:
- TITANIUM
$110.95 -
Hot Cams Titanium Intake Valve for Yamaha WR450F 2003-2009 2011-2015 8400008-3
HOT CAMS
$123.95The factory intake valve is often the weak link in high-revving applications—inadequate sealing leads to compression loss, reduced power delivery, and premature wear. Hot Cams' titanium intake valve replaces that weak point with precision-forged...09262608- SKU:
- 09262608
- Availability:
- Ships Same Business Day
- Weight:
- 0.06 LBS
- MATERIAL:
- NITRIDE COATED
- UNITS:
- EACH
- COLOR/FINISH:
- TITANIUM
- MATERIAL:
- TITANIUM
- PRODUCT NAME:
- VALVE
- RIDING STYLE:
- OFF-ROAD
- APPLICATION:
- INTAKE
- BASE COLOR:
- SILVER
- RIDING STYLE:
- ATV
$123.95 -
Hot Cams Titanium Intake Valve for 2003-2009 Yamaha YZ450F 8400008-2
HOT CAMS
$123.95Stock intake valves on your YZ450F are a limiting factor when you're demanding peak performance lap after lap. The Hot Cams Titanium Intake Valve replaces that weak link with a forged, precision-engineered component that handles aggressive RPMs and...09262607- SKU:
- 09262607
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- MATERIAL:
- NITRIDE COATED
- PRODUCT NAME:
- VALVE
- COLOR/FINISH:
- TITANIUM
- MATERIAL:
- TITANIUM
- APPLICATION:
- CENTER INTAKE
- BASE COLOR:
- SILVER
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$123.95 -
Hot Cams Titanium Exhaust Valve Yamaha YFZ450R 2009-2019 8400008-1
HOT CAMS
$122.95Stock exhaust valves wear out faster under high-load riding conditions, leading to compression loss and reduced performance. The HOT CAMS Titanium Exhaust Valve is engineered with forged construction and hardened surfaces to withstand aggressive use...09262606- SKU:
- 09262606
- Availability:
- Ships Same Business Day
- Weight:
- 0.11 LBS
- BASE COLOR:
- SILVER
- MATERIAL:
- NITRIDE COATED
- UNITS:
- EACH
- COLOR/FINISH:
- TITANIUM
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- VALVE
- MATERIAL:
- TITANIUM
$122.95
