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!
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- Quantity
- Price
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WSM Power Valve Rubber Boot 010-495-05
WSM
$18.53A worn or damaged power valve boot directly impacts your exhaust tuning precision—compromising the responsiveness and peak performance you've dialed in. The WSM Power Valve Rubber Boot 010-495-05 is...09500473- SKU:
- 09500473
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- TYPE:
- POWER VALVE
- UNITS:
- EACH
- RIDING STYLE:
- WATERCRAFT
- PRODUCT NAME:
- BOOT
$18.53 -
MOOSE RACING Crankcase Bearing and Seal Kit 24-1022
MOOSE RACING
$53.95A worn or damaged crankshaft bearing compromises engine reliability and performance—especially critical in 2-stroke engines where bearing failure can cause catastrophic damage. The MOOSE RACING...A241022- SKU:
- A241022
- Availability:
- Ships Same Business Day
- Weight:
- 0.55 LBS
- PRODUCT NAME:
- BEARING KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- RIDING STYLE:
- STREET
- TYPE:
- CRANK
$53.95 -
MOOSE RACING Washer/Snap Ring Counter Shaft 25-6012
MOOSE RACING
$26.95Front sprocket replacements require more than just swapping out the sprocket itself—you need reliable fastening hardware to ensure the countershaft stays secure under load. The MOOSE RACING...09350492- SKU:
- 09350492
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
- PRODUCT NAME:
- SNAP RING
- APPLICATION:
- COUNTERSHAFT
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- 10 PACK
$26.95 -
Twin Air Oil Filter Yamaha WR250F WR250R WR250X WR450F YZ250F YZ250FX YZ450F YZ450FX 140017
TWIN AIR
$11.95Engine protection starts with filtration. A quality oil filter removes contaminants that compromise lubrication and accelerate wear on internal components—especially critical for high-revving...140017- SKU:
- 140017
- Availability:
- Ships Same Business Day
- Weight:
- 0.08 LBS
- RIDING STYLE:
- ATV
- TYPE:
- CARTRIDGE
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- OIL FILTER
- FILTER MEDIA MATERIAL:
- PAPER
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- STYLE:
- STANDARD
$11.95 -
On Sale
PROX Valveshim - 10.00 x 2.60 - 5 pack 29.100260
PROX
MSRP: $9.95Now: $8.00Was: $9.95Valve shims are critical wear items in high-lift, high-RPM engines where precision clearance directly impacts valve timing and engine longevity. The PROX Valveshim 10.00 x 2.60 delivers...09261005- SKU:
- 09261005
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- SHIM KIT
- TYPE:
- VALVE
- UNITS:
- 5 PACK
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- VALVE SHIM THICKNESS METRIC:
- 2.60 MM
MSRP: $9.95Now: $8.00Was: $9.95 -
On Sale
PROX Valveshim - 10.00 x 2.70 - 5 pack 29.100270
PROX
MSRP: $9.95Now: $8.00Was: $9.95Valve shims are critical wear items that directly impact your engine's valve clearance, compression ratio, and overall performance consistency. PROX Valveshims deliver precision-engineered...09261007- SKU:
- 09261007
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- TYPE:
- VALVE
- VALVE SHIM THICKNESS METRIC:
- 2.70 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- PRODUCT NAME:
- SHIM KIT
- UNITS:
- 5 PACK
- RIDING STYLE:
- OFF-ROAD
MSRP: $9.95Now: $8.00Was: $9.95 -
On Sale
PROX Valveshim - 10.00 x 2.75 - 5 pack 29.100275
PROX
MSRP: $9.95Now: $8.00Was: $9.95Valve shim maintenance is critical to engine performance and longevity, yet OEM replacements come with premium pricing that adds up quickly across multiple shims. The PROX Valveshim 10.00 x 2.75...09261008- SKU:
- 09261008
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- TYPE:
- VALVE
- RIDING STYLE:
- OFF-ROAD
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- VALVE SHIM THICKNESS METRIC:
- 2.75 MM
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- UNITS:
- 5 PACK
MSRP: $9.95Now: $8.00Was: $9.95 -
On Sale
PROX Valveshim - 10.00 x 2.80 - 5 pack 29.100280
PROX
MSRP: $9.95Now: $8.00Was: $9.95Valve shim wear directly impacts engine timing precision and performance—especially critical in high-revving builds where tolerance stacking compounds over time. PROX Valveshims deliver...09261009- SKU:
- 09261009
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- TYPE:
- VALVE
- VALVE SHIM THICKNESS METRIC:
- 2.80 MM
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- STREET
- UNITS:
- 5 PACK
MSRP: $9.95Now: $8.00Was: $9.95 -
On Sale
PROX Valveshim - 10.00 x 2.85 - 5 pack 29.100285
PROX
MSRP: $9.95Now: $8.00Was: $9.95Valve shim replacement is one of the most routine maintenance tasks in performance engine building, and using quality OEM-equivalent parts directly impacts your engine's longevity and reliability...09261010- SKU:
- 09261010
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- VALVE SHIM THICKNESS METRIC:
- 2.85 MM
- PRODUCT NAME:
- SHIM KIT
- TYPE:
- VALVE
- UNITS:
- 5 PACK
- RIDING STYLE:
- OFF-ROAD
MSRP: $9.95Now: $8.00Was: $9.95 -
On Sale
PROX Valveshim - 10.00 x 2.90 - 5 pack 29.100290
PROX
MSRP: $9.95Now: $8.00Was: $9.95Valve shim replacement is a critical maintenance task that directly impacts engine performance, valve timing accuracy, and overall reliability. The PROX Valveshim offers a cost-effective alternative...09261011- SKU:
- 09261011
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- PRODUCT NAME:
- SHIM KIT
- TYPE:
- VALVE
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 2.90 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- RIDING STYLE:
- OFF-ROAD
MSRP: $9.95Now: $8.00Was: $9.95 -
On Sale
PROX Valveshim - 10.00 x 3.00 - 5 pack 29.100300
PROX
MSRP: $9.95Now: $8.00Was: $9.95Valve shims are critical wear items that directly impact your engine's valve clearance and overall performance. The PROX 10.00 x 3.00 Valveshim delivers precision engineering at a fraction of OEM...09261013- SKU:
- 09261013
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 3.00 MM
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- TYPE:
- VALVE
- RIDING STYLE:
- OFF-ROAD
MSRP: $9.95Now: $8.00Was: $9.95 -
On Sale
PROX Valveshim - 10.00 x 3.05 - 5 pack 29.100305
PROX
MSRP: $9.95Now: $8.00Was: $9.95Valve shim clearance directly impacts engine performance, longevity, and reliability—and worn or incorrect shims lead to costly valve damage and downtime. The PROX Valveshim offers...09261014- SKU:
- 09261014
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- PRODUCT NAME:
- SHIM KIT
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 3.05 MM
- RIDING STYLE:
- OFF-ROAD
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- TYPE:
- VALVE
MSRP: $9.95Now: $8.00Was: $9.95 -
On Sale
PROX Valveshim - 10.00 x 3.20 - 5 pack 29.100320
PROX
MSRP: $9.95Now: $8.00Was: $9.95Valve shim wear directly impacts engine timing and compression—critical factors in maintaining peak performance and reliability. PROX Valveshims deliver OEM-quality replacement at a fraction of the...09261017- SKU:
- 09261017
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- VALVE SHIM THICKNESS METRIC:
- 3.20 MM
- PRODUCT NAME:
- SHIM KIT
- UNITS:
- 5 PACK
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- TYPE:
- VALVE
MSRP: $9.95Now: $8.00Was: $9.95 -
On Sale
PROX Valve and Spring Kit 28.SIS1405-2
PROX
MSRP: $143.95Now: $119.00Was: $143.95If you're running your engine hard at high RPM, stock valve springs will eventually fail you—they simply aren't engineered for sustained extreme conditions. The PROX Valve and Spring Kit 28.SIS1405-2...09261021- SKU:
- 09261021
- Availability:
- Ships Same Business Day
- Weight:
- 0.34 LBS
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- PRODUCT NAME:
- SPRING KIT
- TYPE:
- VALVE
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
MSRP: $143.95Now: $119.00Was: $143.95 -
On Sale
PROX Valve and Spring Kit 28.SES2424-1
PROX
MSRP: $143.95Now: $119.00Was: $143.95If you're pushing your engine to the limit, your OEM valve train becomes the weak link. The PROX 28.SES2424-1 replaces stock valves and springs with nitrided steel components engineered to withstand...09261025- SKU:
- 09261025
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
- TYPE:
- VALVE
- PRODUCT NAME:
- SPRING KIT
- APPLICATION:
- EXHAUST
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
MSRP: $143.95Now: $119.00Was: $143.95 -
On Sale
PROX Valve and Spring Kit 28.SIS4406-2
PROX
MSRP: $159.95Now: $136.00Was: $159.95If you're running your engine hard at sustained high RPM, your OEM valve train becomes the weak link. The PROX Valve and Spring Kit 28.SIS4406-2 upgrades both your valves and springs to handle the...09261031- SKU:
- 09261031
- Availability:
- Ships Same Business Day
- Weight:
- 0.36 LBS
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- APPLICATION:
- INTAKE
- PRODUCT NAME:
- SPRING KIT
- TYPE:
- VALVE
MSRP: $159.95Now: $136.00Was: $159.95 -
On Sale
PROX Valve and Spring Kit 28.SIS4409-2
PROX
MSRP: $166.95Now: $136.00Was: $166.95If you're pushing your engine to its limits, OEM valves and springs won't cut it. The PROX Valve and Spring Kit 28.SIS4409-2 replaces stock components with nitrided steel valves and premium chrome...09261033- SKU:
- 09261033
- Availability:
- Ships Same Business Day
- Weight:
- 0.35 LBS
- UNITS:
- KIT
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- SPRING KIT
- TYPE:
- VALVE
MSRP: $166.95Now: $136.00Was: $166.95 -
On Sale
PROX Valve and Spring Kit 28.SES4409-1
PROX
MSRP: $166.95Now: $136.00Was: $166.95If you're pushing your engine beyond stock parameters, OEM valves and springs will become your bottleneck. The PROX 28.SES4409-1 replaces factory components with nitrided steel valves and premium...09261034- SKU:
- 09261034
- Availability:
- Ships Same Business Day
- Weight:
- 0.30 LBS
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- APPLICATION:
- EXHAUST
- PRODUCT NAME:
- SPRING KIT
- TYPE:
- VALVE
MSRP: $166.95Now: $136.00Was: $166.95 -
On Sale
PROX Valve and Spring Kit 28.SIS3405-2
PROX
MSRP: $139.95Now: $119.00Was: $139.95If you're pushing your engine to high RPM territory, factory valve and spring assemblies become your limiting factor. The PROX 28.SIS3405-2 replaces weak OEM components with nitrided steel valves and...09261035- SKU:
- 09261035
- Availability:
- Ships Same Business Day
- Weight:
- 0.31 LBS
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
- TYPE:
- VALVE
- APPLICATION:
- INTAKE
- PRODUCT NAME:
- SPRING KIT
MSRP: $139.95Now: $119.00Was: $139.95 -
On Sale
PROX Valve and Spring Kit 28.SIS3408-2
PROX
MSRP: $143.95Now: $119.00Was: $143.95If you're pushing your engine beyond stock limits, OEM valves and springs become your weak link. The PROX 28.SIS3408-2 Valve and Spring Kit replaces those components with hardened steel valves and...09261039- SKU:
- 09261039
- Availability:
- Ships Same Business Day
- Weight:
- 0.32 LBS
- PRODUCT NAME:
- SPRING KIT
- TYPE:
- VALVE
- APPLICATION:
- INTAKE
- MATERIAL:
- STEEL
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- KIT
MSRP: $143.95Now: $119.00Was: $143.95
