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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PROX Valve Shim - 5 pack 29.948285
PROX
$10.95Valve shim selection directly impacts your engine's valve clearance, combustion efficiency, and component longevity. The PROX Valve Shim 5-pack delivers precision-engineered shims with heat-treated...09260975- SKU:
- 09260975
- 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
- VALVE SHIM THICKNESS METRIC:
- 2.85 MM
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
$10.95 -
PROX Valve Shim - 5 pack 29.948290
PROX
$10.95Valve shim clearance directly impacts engine performance, combustion efficiency, and component longevity. PROX Valve Shims are precision-machined to exact tolerances, eliminating guesswork during...09260976- SKU:
- 09260976
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- UNITS:
- 5 PACK
- RIDING STYLE:
- STREET
- RIDING STYLE:
- WATERCRAFT
- RIDING STYLE:
- OFF-ROAD
- VALVE SHIM THICKNESS METRIC:
- 2.90 MM
- OUTSIDE DIAMETER METRIC:
- 9.48 MM
- RIDING STYLE:
- ATV
- TYPE:
- VALVE
$10.95 -
PROX Valve Shim Kit 29.VSA1000
PROX
$99.95Valve shims are critical wear items that directly impact valve clearance, combustion efficiency, and engine longevity. OEM replacements come with premium pricing and extended lead times—the PROX...09260989- SKU:
- 09260989
- Availability:
- Ships Same Business Day
- Weight:
- 0.67 LBS
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- RIDING STYLE:
- STREET
- PRODUCT NAME:
- SHIM KIT
- RIDING STYLE:
- SNOW
- RIDING STYLE:
- UTV
- TYPE:
- VALVE
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- ATV
- VALVE SHIM THICKNESS METRIC:
- 1.85 MM - 3.20 MM
- RIDING STYLE:
- OFF-ROAD
- RIDING STYLE:
- WATERCRAFT
- UNITS:
- KIT
$99.95 -
PROX Valveshim - 10.00 x 2.20 - 5 pack 29.100220
PROX
$9.95Valve shims are critical wear components that directly impact your engine's valvetrain precision and longevity. OEM replacements are expensive and require frequent servicing—PROX valveshims deliver...09260997- SKU:
- 09260997
- Availability:
- Ships Same Business Day
- Weight:
- 0.02 LBS
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- VALVE
- OUTSIDE DIAMETER METRIC:
- 10.00 MM
- RIDING STYLE:
- ADVENTURE TOURING / DUAL-SPORT
- RIDING STYLE:
- STREET
- VALVE SHIM THICKNESS METRIC:
- 2.20 MM
- PRODUCT NAME:
- SHIM KIT
- UNITS:
- 5 PACK
$9.95 -
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 01.1338.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 01.2406.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 01.3338.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 01.4337.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.C
PROX
$189.95When your engine is pushing limits, your pistons need to match that intensity. The PROX Piston Kit 01.4406.C delivers OEM-equivalent reliability with Japanese manufacturing precision, ensuring...09101158- SKU:
- 09101158
- Availability:
- Ships Same Business Day
- Weight:
- 0.92 LBS
- PISTON DIAMETER METRIC:
- 95.99 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE C
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 95.99 MM
- PRODUCT NAME:
- PISTON KIT
$189.95 -
PROX Piston Kit 01.6105.A
PROX
$105.95Your engine's heart deserves precision engineering built to last. The PROX Piston Kit 01.6105.A delivers OEM-grade reliability with the exacting tolerances demanded by both stock rebuilds and...09101159- SKU:
- 09101159
- Availability:
- Ships Same Business Day
- Weight:
- 0.29 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 46.95 MM
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 46.95 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
$105.95 -
PROX Piston Kit 01.6105.B
PROX
$105.95When your engine's pistons wear beyond OEM tolerances, performance and reliability suffer. The PROX Piston Kit 01.6105.B delivers factory-spec replacement pistons engineered to restore combustion...09101160- SKU:
- 09101160
- Availability:
- Ships Same Business Day
- Weight:
- 0.29 LBS
- PISTON DIAMETER METRIC:
- 46.96 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 46.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
$105.95 -
PROX Piston Kit 01.6105.C
PROX
$105.95Piston failure cuts a race or rebuild short. The PROX Piston Kit 01.6105.C delivers OEM-equivalent reliability with precision engineering, ensuring your engine maintains peak combustion efficiency...09101161- SKU:
- 09101161
- Availability:
- Ships Same Business Day
- Weight:
- 0.29 LBS
- BORE SIZE METRIC:
- 46.97 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 46.97 MM
- PISTON SIZE METRIC:
- STANDARD SIZE C
- PRODUCT NAME:
- PISTON KIT
$105.95 -
PROX Piston Kit 01.6105.D
PROX
$105.95Your engine's pistons are the hardest-working components under the hood, cycling thousands of times per minute while managing extreme heat and pressure. When OEM pistons wear out or fail, you need a...09101162- SKU:
- 09101162
- Availability:
- Ships Same Business Day
- Weight:
- 0.28 LBS
- PISTON DIAMETER METRIC:
- 46.98 MM
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 46.98 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE D
$105.95 -
PROX Piston Kit 01.6343.D
PROX
$166.95When your engine's pistons show wear, you're looking at compromised compression, increased blow-by, and accelerated internal degradation. The PROX Piston Kit 01.6343.D delivers OEM-equivalent...09101166- SKU:
- 09101166
- Availability:
- Ships Same Business Day
- Weight:
- 0.67 LBS
- PISTON DIAMETER METRIC:
- 66.37 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- BORE SIZE METRIC:
- 66.37 MM
- PISTON SIZE METRIC:
- STANDARD SIZE D
- PRODUCT NAME:
- PISTON KIT
$166.95 -
PROX Piston Kit 01.6521.B
PROX
$221.95When your engine is running on stock pistons, you're leaving performance on the table and risking catastrophic failure under sustained boost or high RPM loads. The PROX Piston Kit 01.6521.B delivers...09101183- SKU:
- 09101183
- Availability:
- Ships Same Business Day
- Weight:
- 0.91 LBS
- PISTON DIAMETER METRIC:
- 94.95 MM
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 94.95 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- ATV
- UNITS:
- EACH
$221.95 -
PROX Piston Kit 01.6521.C
PROX
$221.95Worn or damaged pistons compromise engine efficiency, power delivery, and reliability—especially in high-demand racing and performance applications. The PROX Piston Kit 01.6521.C delivers...09101184- SKU:
- 09101184
- Availability:
- Ships Same Business Day
- Weight:
- 0.90 LBS
- BORE SIZE METRIC:
- 94.96 MM
- PISTON DIAMETER METRIC:
- 94.96 MM
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- ATV
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
- UNITS:
- EACH
$221.95
