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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On Sale
PROX Top End Gasket Set - Beta 35.7219
PROX
MSRP: $51.95Now: $42.00Was: $51.95A top-end rebuild demands precision sealing—any leak compromises compression, performance, and reliability. The PROX Top End Gasket Set delivers OEM-equivalent quality through factory-controlled...09347780- SKU:
- 09347780
- Availability:
- Ships Same Business Day
- Weight:
- 0.15 LBS
MSRP: $51.95Now: $42.00Was: $51.95 -
On Sale
PROX Top End Gasket Set - Beta 35.7220
PROX
MSRP: $51.95Now: $42.00Was: $51.95A top-end rebuild demands gasket integrity that won't compromise your engine's sealing surfaces or performance gains. The PROX Top End Gasket Set delivers OEM-equivalent quality without the premium...09347781- SKU:
- 09347781
- Availability:
- Ships Same Business Day
- Weight:
- 0.15 LBS
MSRP: $51.95Now: $42.00Was: $51.95 -
On Sale
PROX Top End Gasket Set - Beta 35.7313
PROX
MSRP: $62.95Now: $51.00Was: $62.95A compromised top-end gasket set will leak compression, rob horsepower, and leave you stranded. The PROX 35.7313 delivers the complete gasket set you need for a proper rebuild, engineered to seal...09347782- SKU:
- 09347782
- Availability:
- Ships Same Business Day
- Weight:
- 0.15 LBS
MSRP: $62.95Now: $51.00Was: $62.95 -
On Sale
PROX Top End Gasket Set - Sherco 35.7314
PROX
MSRP: $88.95Now: $72.00Was: $88.95A leaking or worn top-end gasket set will compromise your Sherco's compression, throttle response, and overall reliability—especially critical if you're running lean jetting or pushing higher RPMs...09347783- SKU:
- 09347783
- Availability:
- Ships Same Business Day
- Weight:
- 0.10 LBS
MSRP: $88.95Now: $72.00Was: $88.95 -
On Sale
PROX Top End Gasket Set - Beta 35.7322
PROX
MSRP: $62.95Now: $51.00Was: $62.95A top-end rebuild demands precision sealing—any leak or gasket failure can compromise compression, reduce power output, and lead to costly engine damage. The PROX Top End Gasket Set delivers...09347784- SKU:
- 09347784
- Availability:
- Ships Same Business Day
- Weight:
- 0.22 LBS
MSRP: $62.95Now: $51.00Was: $62.95 -
On Sale
PROX Top End Gasket Set - Beta 35.7323
PROX
MSRP: $62.95Now: $51.00Was: $62.95A top-end rebuild demands precision-fit gaskets that seal reliably under extreme combustion pressures and temperature cycling. The PROX Top End Gasket Set delivers factory-spec tolerances and...09347785- SKU:
- 09347785
- Availability:
- Ships Same Business Day
- Weight:
- 0.22 LBS
MSRP: $62.95Now: $51.00Was: $62.95 -
On Sale
PROX Top End Gasket Set - Sherco 35.7324
PROX
MSRP: $99.95Now: $81.00Was: $99.95A degraded top-end gasket set compromises engine sealing, reducing compression and inviting coolant or oil seepage that can sideline your Sherco mid-season. The PROX 35.7324 delivers OEM-grade...09347786- SKU:
- 09347786
- Availability:
- Ships Same Business Day
- Weight:
- 0.18 LBS
MSRP: $99.95Now: $81.00Was: $99.95 -
On Sale
PROX Top End Gasket Set - Beta 35.7332
PROX
MSRP: $62.95Now: $51.00Was: $62.95A top-end rebuild demands precision sealing—any leak compromises compression, power delivery, and engine longevity. The PROX Top End Gasket Set delivers OEM-quality sealing with factory...09347787- SKU:
- 09347787
- Availability:
- Ships Same Business Day
- Weight:
- 0.22 LBS
MSRP: $62.95Now: $51.00Was: $62.95 -
On Sale
PROX Top End Gasket Set - Beta 35.7351
PROX
MSRP: $130.95Now: $106.00Was: $130.95A degraded top-end gasket set compromises compression, invites oil leakage, and forces you into unnecessary downtime. The PROX 35.7351 delivers OEM-equivalent sealing across all critical junctions,...09347788- SKU:
- 09347788
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
MSRP: $130.95Now: $106.00Was: $130.95 -
On Sale
PROX Top End Gasket Set - Beta 35.7360
PROX
MSRP: $130.95Now: $106.00Was: $130.95A top-end rebuild demands precision—and this gasket set delivers the sealing integrity your engine needs to perform reliably under race conditions or high-demand use. ProX engineered each gasket to...09347789- SKU:
- 09347789
- Availability:
- Ships Same Business Day
- Weight:
- 0.20 LBS
MSRP: $130.95Now: $106.00Was: $130.95 -
On Sale
PROX Top End Gasket Set - Beta 35.7416
PROX
MSRP: $130.95Now: $106.00Was: $130.95A top-end rebuild demands precision sealing—any compromise risks compression loss, coolant seepage, and catastrophic engine failure. The PROX Top End Gasket Set (35.7416) delivers OEM-quality...09347790- SKU:
- 09347790
- Availability:
- Ships Same Business Day
- Weight:
- 0.15 LBS
MSRP: $130.95Now: $106.00Was: $130.95 -
On Sale
PROX Top End Gasket Set - Beta 35.7420
PROX
MSRP: $130.95Now: $106.00Was: $130.95A compromised top-end gasket set will cost you power, reliability, and eventually, engine damage. The PROX Top End Gasket Set (35.7420) delivers the precision sealing your Beta engine needs to...09347791- SKU:
- 09347791
- Availability:
- Ships Same Business Day
- Weight:
- 0.15 LBS
MSRP: $130.95Now: $106.00Was: $130.95 -
On Sale
PROX Top End Gasket Set - Beta 35.7426
PROX
MSRP: $130.95Now: $106.00Was: $130.95A worn top-end gasket set compromises combustion sealing, leading to compression loss and decreased power output. The PROX 35.7426 restores proper sealing integrity across your top-end, ensuring...09347792- SKU:
- 09347792
- Availability:
- Ships Same Business Day
- Weight:
- 0.15 LBS
MSRP: $130.95Now: $106.00Was: $130.95 -
On Sale
PROX Top End Gasket Set - Beta 35.7430
PROX
MSRP: $130.95Now: $106.00Was: $130.95When you're rebuilding your Beta's top end, a failed gasket means catastrophic oil loss, coolant leaks, and potential engine damage—none of which you can afford mid-season. The PROX Top End Gasket...09347793- SKU:
- 09347793
- Availability:
- Ships Same Business Day
- Weight:
- 0.15 LBS
MSRP: $130.95Now: $106.00Was: $130.95 -
On Sale
PROX Piston Kit - 78.97 mm - Honda CRF250R/CRF250RX 01.1350.A
PROX
MSRP: $188.95Now: $158.00Was: $188.95A worn or damaged piston compromises engine compression, throttle response, and overall reliability—especially critical in a high-revving 250cc four-stroke. The PROX Piston Kit delivers...09106779- SKU:
- 09106779
- Availability:
- Ships Same Business Day
- Weight:
- 0.53 LBS
MSRP: $188.95Now: $158.00Was: $188.95 -
On Sale
PROX Piston Kit - 53.95 mm - Yamaha YZ125/YZ125X 01.2232.A
PROX
MSRP: $121.95Now: $90.00Was: $121.95A worn or damaged piston directly compromises your YZ125/YZ125X's power delivery, compression, and engine reliability. The PROX 53.95 mm Piston Kit restores your engine to OEM performance...09106780- SKU:
- 09106780
- Availability:
- Ships Same Business Day
- Weight:
- 0.45 LBS
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit - 96.95 mm - Yamaha WR450F/YZ450F/YZ450FX 01.2448.A
PROX
MSRP: $210.95Now: $167.00Was: $210.95When your Yamaha WR450F or YZ450F demands more from its engine, a quality piston kit is non-negotiable. This PROX kit delivers precision-machined components engineered to exact OEM specifications,...09106781- SKU:
- 09106781
- Availability:
- Ships Same Business Day
- Weight:
- 0.55 LBS
MSRP: $210.95Now: $167.00Was: $210.95 -
On Sale
PROX Piston Kit - 96.95 mm - Yamaha WR450F/YZ450F/YZ450FX 01.2450.A
PROX
MSRP: $221.95Now: $183.00Was: $221.95A piston kit is one of the most critical components in your engine's combustion chamber—it directly impacts power delivery, reliability, and longevity. The PROX 96.95 mm kit for your...09106782- SKU:
- 09106782
- Availability:
- Ships Same Business Day
- Weight:
- 1.00 LBS
MSRP: $221.95Now: $183.00Was: $221.95 -
On Sale
PROX Piston Kit - 96.95 mm - Yamaha WR450F/YZ450F/YZ450FX 01.2453.A
PROX
MSRP: $221.95Now: $183.00Was: $221.95A worn or damaged piston directly impacts your WR450F or YZ450F's compression ratio, throttle response, and overall reliability—especially under high-RPM racing conditions. This PROX piston kit...09106783- SKU:
- 09106783
- Availability:
- Ships Same Business Day
- Weight:
- 0.93 LBS
MSRP: $221.95Now: $183.00Was: $221.95 -
On Sale
PROX Piston Kit - 77.96 mm - Kawasaki KX250/KX250X 01.4353.A
PROX
MSRP: $188.95Now: $158.00Was: $188.95The piston is the heart of your engine's combustion cycle—wear, scoring, or improper tolerances kill power and reliability. This PROX kit delivers OEM-equivalent precision for the Kawasaki...09106787- SKU:
- 09106787
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
MSRP: $188.95Now: $158.00Was: $188.95
