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 - 5 pack 29.890260
PROX
$9.95Valve shims are wear items that demand precision replacement—using undersized or poorly machined shims leads to valve train instability, timing issues, and potential engine damage. PROX Valveshims...09260940- SKU:
- 09260940
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- OUTSIDE DIAMETER METRIC:
- 8.90 MM
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- STREET
- RIDING STYLE:
- UTV
- VALVE SHIM THICKNESS METRIC:
- 2.60 MM
$9.95Qty in Cart: 0Quantity:Price:$9.95Subtotal: -
PROX Valve Shim - 5 pack 29.948125
PROX
$9.95Valve shim selection directly impacts your engine's performance, reliability, and tuning precision. These PROX shims are heat-treated to exacting standards, delivering the dimensional consistency...09260943- SKU:
- 09260943
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- RIDING STYLE:
- STREET
- RIDING STYLE:
- UTV
- VALVE SHIM THICKNESS METRIC:
- 1.25 MM
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
$9.95 -
PROX Valve Shim - 5 pack 29.948140
PROX
$10.95Valve train precision directly impacts engine reliability and performance consistency. PROX Valve Shims are heat-treated and machined to exact tolerances, ensuring proper valve clearance and...09260946- SKU:
- 09260946
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- RIDING STYLE:
- STREET
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- TYPE:
- VALVE
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 1.40 MM
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- WATERCRAFT
$10.95 -
PROX Valve Shim - 5 pack 29.948145
PROX
$10.95Valve shim clearance directly impacts engine timing, power delivery, and component longevity—making precision fitment non-negotiable for serious builders. PROX shims are heat-treated to resist wear...09260947- SKU:
- 09260947
- Availability:
- Ships Same Business Day
- Weight:
- 0.01 LBS
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ATV
- RIDING STYLE:
- STREET
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- UTV
- TYPE:
- VALVE
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 1.45 MM
$10.95 -
PROX Valve Shim - 5 pack 29.948155
PROX
$10.95Valve shimming is critical for maintaining precise valve clearances, and worn or incorrect shims lead to poor combustion timing, reduced power output, and accelerated component wear. The PROX Valve...09260949- SKU:
- 09260949
- Availability:
- Ships Same Business Day
- Weight:
- 0.01 LBS
- RIDING STYLE:
- ATV
- TYPE:
- VALVE
- RIDING STYLE:
- STREET
- RIDING STYLE:
- WATERCRAFT
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- OFF-ROAD
- VALVE SHIM THICKNESS METRIC:
- 1.55 MM
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- UNITS:
- 5 PACK
$10.95 -
PROX Valve Shim - 5 pack 29.948160
PROX
$10.95Valve shim wear directly impacts your engine's compression, valve timing, and overall performance consistency—especially in high-RPM or forced induction applications. This 5-pack of PROX shims gives...09260950- SKU:
- 09260950
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 1.60 MM
- RIDING STYLE:
- STREET
- RIDING STYLE:
- UTV
$10.95 -
PROX Valve Shim - 5 pack 29.948165
PROX
$10.95Valve shim selection directly impacts your engine's precision timing and overall performance reliability. PROX Valve Shims maintain exact clearance tolerances across extended operating cycles,...09260951- SKU:
- 09260951
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- VALVE SHIM THICKNESS METRIC:
- 1.65 MM
- RIDING STYLE:
- STREET
$10.95 -
PROX Valve Shim - 5 pack 29.948170
PROX
$10.95Valve shims are critical to maintaining precise valve clearance and ensuring consistent engine performance across heat cycles. Over time, stock shims wear and degrade, leading to increased clearance...09260952- SKU:
- 09260952
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- RIDING STYLE:
- ATV
- TYPE:
- VALVE
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- STREET
- RIDING STYLE:
- WATERCRAFT
- VALVE SHIM THICKNESS METRIC:
- 1.70 MM
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- UNITS:
- 5 PACK
$10.95 -
PROX Valve Shim - 5 pack 29.948175
PROX
$10.95Valve shimming is critical to maintaining proper valve clearance and ensuring your engine operates at peak efficiency. These PROX shims are precision-machined to exact tolerances and heat-treated for...09260953- SKU:
- 09260953
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
- RIDING STYLE:
- STREET
- RIDING STYLE:
- WATERCRAFT
- VALVE SHIM THICKNESS METRIC:
- 1.75 MM
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- UNITS:
- 5 PACK
$10.95 -
PROX Valve Shim - 5 pack 29.948180
PROX
$10.95Valve shimming is critical for maintaining precise valve clearances in high-performance and racing engines—even small deviations can compromise power delivery, fuel efficiency, and component...09260954- SKU:
- 09260954
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- RIDING STYLE:
- STREET
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- TYPE:
- VALVE
- UNITS:
- 5 PACK
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- ATV
- VALVE SHIM THICKNESS METRIC:
- 1.80 MM
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- WATERCRAFT
$10.95 -
PROX Valve Shim - 5 pack 29.948185
PROX
$10.95Valve shim selection directly impacts your engine's ability to maintain precise valve clearances under high RPM and extreme heat. PROX Valve Shims deliver the hardness and dimensional accuracy...09260955- SKU:
- 09260955
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- STREET
- VALVE SHIM THICKNESS METRIC:
- 1.85 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- ATV
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- TYPE:
- VALVE
- UNITS:
- 5 PACK
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- WATERCRAFT
$10.95 -
PROX Valve Shim - 5 pack 29.948190
PROX
$10.95Valve shim selection directly impacts your engine's valve clearance accuracy and overall reliability under sustained performance conditions. PROX shims are precision-machined to exacting tolerances,...09260956- SKU:
- 09260956
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- STREET
- RIDING STYLE:
- UTV
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
- VALVE SHIM THICKNESS METRIC:
- 1.90 MM
$10.95 -
PROX Valve Shim - 5 pack 29.948195
PROX
$10.95Valve shims are critical for maintaining proper valve clearance and preventing catastrophic engine damage from improper gap settings. This PROX 5-pack ensures you have precision replacements on hand...09260957- SKU:
- 09260957
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- RIDING STYLE:
- STREET
- RIDING STYLE:
- UTV
- VALVE SHIM THICKNESS METRIC:
- 1.95 MM
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
$10.95 -
PROX Valve Shim - 5 pack 29.948200
PROX
$10.95Valve shim clearance directly impacts your engine's reliability and performance—improper specs lead to valve float, bent pushrods, and catastrophic failure. PROX valve shims are precision-machined to...09260958- SKU:
- 09260958
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- UNITS:
- 5 PACK
- VALVE SHIM THICKNESS METRIC:
- 2.00 MM
- RIDING STYLE:
- STREET
- RIDING STYLE:
- WATERCRAFT
- RIDING STYLE:
- OFF-ROAD
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ATV
- TYPE:
- VALVE
$10.95 -
PROX Valve Shim - 5 pack 29.948205
PROX
$10.95Valve shim clearance directly impacts engine efficiency, combustion timing, and component longevity. PROX valve shims are precision-machined to exacting tolerances, eliminating guesswork during valve...09260959- SKU:
- 09260959
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- UNITS:
- 5 PACK
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- STREET
- RIDING STYLE:
- WATERCRAFT
- RIDING STYLE:
- ATV
- TYPE:
- VALVE
- VALVE SHIM THICKNESS METRIC:
- 2.05 MM
$10.95 -
PROX Valve Shim - 5 pack 29.948210
PROX
$10.95Valve shim clearance directly impacts engine performance, combustion efficiency, and component longevity. If your shims are worn or incorrectly sized, you'll experience valve float, compression loss,...09260960- SKU:
- 09260960
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- STREET
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- ATV
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- TYPE:
- VALVE
- UNITS:
- 5 PACK
- RIDING STYLE:
- WATERCRAFT
- VALVE SHIM THICKNESS METRIC:
- 2.10 MM
$10.95 -
PROX Valve Shim - 5 pack 29.948215
PROX
$10.95Valve train precision directly impacts engine reliability and performance consistency. These PROX shims are heat-treated to resist wear and maintain exact tolerances through countless combustion...09260961- SKU:
- 09260961
- Availability:
- Ships Same Business Day
- Weight:
- 0.03 LBS
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- STREET
- VALVE SHIM THICKNESS METRIC:
- 2.15 MM
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- TYPE:
- VALVE
- UNITS:
- 5 PACK
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- WATERCRAFT
$10.95 -
PROX Valve Shim - 5 pack 29.948220
PROX
$10.95Valve shim selection directly impacts your engine's valve clearance, compression ratio, and overall top-end performance. PROX Valve Shims are precision-machined to exact tolerances and heat-treated...09260962- SKU:
- 09260962
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- RIDING STYLE:
- STREET
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- VALVE SHIM THICKNESS METRIC:
- 2.20 MM
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- TYPE:
- VALVE
- UNITS:
- 5 PACK
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- WATERCRAFT
$10.95 -
PROX Valve Shim - 5 pack 29.948225
PROX
$10.95Valve train geometry directly impacts engine performance, and worn or improperly sized shims compromise both power delivery and component longevity. The PROX Valve Shim 5-pack delivers...09260963- SKU:
- 09260963
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- RIDING STYLE:
- STREET
- RIDING STYLE:
- UTV
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- VALVE SHIM THICKNESS METRIC:
- 2.25 MM
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
$10.95 -
PROX Valve Shim - 5 pack 29.948230
PROX
$10.95Valve shim precision directly impacts engine reliability and performance consistency across your entire powerband. These PROX shims are heat-treated for superior hardness, reducing wear and extending...09260964- SKU:
- 09260964
- Availability:
- Ships Same Business Day
- Weight:
- 0.05 LBS
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- 5 PACK
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- UTV
- TYPE:
- VALVE
- RIDING STYLE:
- ATV
- RIDING STYLE:
- STREET
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- VALVE SHIM THICKNESS METRIC:
- 2.30 MM
$10.95
