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
PROX Piston Kit - 57.94 mm - Husqvarna TE150i | KTM 150EXC TPI 01.6241.A
PROX
MSRP: $139.95Now: $119.00Was: $139.95A worn or damaged piston directly compromises engine compression, throttle response, and overall reliability—especially critical on high-revving 150cc two-stroke engines. The PROX 57.94 mm Piston Kit delivers OEM-equivalent performance with Japanese...09106792- SKU:
- 09106792
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
MSRP: $139.95Now: $119.00Was: $139.95 -
On Sale
PROX Piston Kit - 87.96 mm - Gas Gas | Husqvarna | KTM 01.6353.A
PROX
MSRP: $209.95Now: $195.00Was: $229.73Whether you're rebuilding a top-end after a hard race season or restoring a two-stroke to factory specifications, a precision piston kit is non-negotiable. The PROX 87.96 mm Piston Kit delivers OEM-quality components that restore compression, seal...09106793- SKU:
- 09106793
- Availability:
- Ships Same Business Day
- Weight:
- 0.45 LBS
MSRP: $209.95Now: $195.00Was: $229.73 -
On Sale
PROX Piston Kit - 94.95 mm - Gas Gas | Husqvarna | KTM 01.6434.A
PROX
MSRP: $221.95Now: $183.00Was: $221.95A worn or damaged piston directly compromises engine compression, power delivery, and reliability—especially critical in high-demand 2-stroke applications. The PROX Piston Kit delivers OEM-grade precision machining and ring specifications, ensuring your...09106794- SKU:
- 09106794
- Availability:
- Ships Same Business Day
- Weight:
- 1.00 LBS
MSRP: $221.95Now: $183.00Was: $221.95Qty in Cart: 0Quantity:Price:MSRP: $221.95Now: $183.00Was: $221.95Subtotal: -
On Sale
PROX Piston Kit - 94.95 mm - Husqvarna FE450 | KTM 450EXC-F 01.6440.A
PROX
MSRP: $221.95Now: $167.00Was: $221.95The piston is the heart of your engine's combustion process, and a worn or damaged unit directly compromises power delivery, fuel efficiency, and reliability. This PROX kit delivers OEM-quality components precision-machined to exact tolerances, ensuring...09106795- SKU:
- 09106795
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
MSRP: $221.95Now: $167.00Was: $221.95 -
On Sale
PROX Piston Kit - 94.96 mm - Gas Gas | Husqvarna | KTM 01.6443.A
PROX
MSRP: $214.95Now: $183.00Was: $214.95Engine wear demands precision replacement, and OEM-equivalent pistons are non-negotiable for maintaining compression, power delivery, and reliability. The PROX 94.96 mm piston kit delivers factory-spec performance across Gas Gas, Husqvarna, and KTM...09106796- SKU:
- 09106796
- Availability:
- Ships Same Business Day
- Weight:
- 0.83 LBS
MSRP: $214.95Now: $183.00Was: $214.95 -
On Sale
PROX Piston Kit - 94.95 mm - Gas Gas | Husqvarna | KTM 01.6513.A
PROX
MSRP: $221.95Now: $183.00Was: $221.95A worn or damaged piston directly impacts combustion efficiency, throttle response, and overall engine longevity—making a quality replacement essential for maintaining peak performance. The PROX 94.95 mm Piston Kit delivers OEM-spec precision with...09106797- SKU:
- 09106797
- Availability:
- Ships Same Business Day
- Weight:
- 0.78 LBS
MSRP: $221.95Now: $183.00Was: $221.95 -
On Sale
PROX Piston Kit - 66.34 mm - Beta RR250/Xtrainer 250 01.7313.A
PROX
MSRP: $159.95Now: $136.00Was: $159.95When your Beta RR250 or Xtrainer 250 demands a fresh top-end rebuild, settling for substandard pistons compromises both reliability and performance. This PROX piston kit delivers OEM-quality engineering with precision CNC-machining and high-silicon...09106798- SKU:
- 09106798
- Availability:
- Ships Same Business Day
- Weight:
- 0.75 LBS
MSRP: $159.95Now: $136.00Was: $159.95 -
On Sale
PROX Piston Kit - 75.96 mm - Sherco 250SE-F/250SEF-R 01.7314.A
PROX
MSRP: $209.99Now: $178.00Was: $209.99Your Sherco 250SE engine demands precision components that match OEM specifications without compromise. This PROX piston kit delivers CNC-machined accuracy and OEM-spec rings in a complete assembly, eliminating the guesswork of sourcing individual...09106799- SKU:
- 09106799
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
MSRP: $209.99Now: $178.00Was: $209.99 -
On Sale
PROX Piston Kit - 83.95 mm - Sherco 300SE-F/300SEF-R 01.7324.A
PROX
MSRP: $221.95Now: $178.00Was: $221.95Your Sherco 300SE-F/300SEF-R demands precision internals that can withstand the demands of high-RPM racing and aggressive trail riding. This PROX piston kit delivers OEM-quality components engineered to exact specifications, ensuring reliable power...09106800- SKU:
- 09106800
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
MSRP: $221.95Now: $178.00Was: $221.95 -
On Sale
PROX Piston Kit - 66.34 mm - Sherco 250SE/250SE-R 01.7334.A
PROX
MSRP: $166.95Now: $136.00Was: $166.95When your Sherco 250SE/250SE-R's piston begins to show wear, power delivery suffers and reliability becomes uncertain. This PROX piston kit restores your engine to OEM performance standards with precision-engineered components built to withstand the...09106801- SKU:
- 09106801
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
MSRP: $166.95Now: $136.00Was: $166.95 -
On Sale
PROX Piston Kit - 66.34 mm - Sherco 250SE/250SE-R 01.7337.A
PROX
MSRP: $166.95Now: $136.00Was: $166.95When your Sherco 250SE or 250SE-R piston shows wear, compression loss and power degradation follow. This PROX piston kit restores factory performance and reliability with precision engineering, giving you the responsiveness and durability you need...09106802- SKU:
- 09106802
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
MSRP: $166.95Now: $136.00Was: $166.95 -
On Sale
PROX Piston Kit - 71.94 mm - Sherco 300SE/300SE-R 01.7346.A
PROX
MSRP: $221.95Now: $170.00Was: $221.95A worn or damaged piston directly compromises combustion efficiency, power delivery, and engine longevity in your Sherco 300SE/300SE-R. This PROX piston kit restores factory performance with precision-engineered components that meet or exceed OEM...09106803- SKU:
- 09106803
- Availability:
- Ships Same Business Day
- Weight:
- 0.80 LBS
MSRP: $221.95Now: $170.00Was: $221.95 -
On Sale
PROX Piston Kit - 87.96 mm - Beta 350RR 01.7351.A
PROX
MSRP: $221.95Now: $178.00Was: $221.95Engine wear compromises power delivery and reliability—a quality piston kit restores your Beta 350RR to factory specifications and beyond. This PROX kit delivers OEM-grade precision with a complete assembly, eliminating guesswork and potential fitment...09106804- SKU:
- 09106804
- Availability:
- Ships Same Business Day
- Weight:
- 0.69 LBS
MSRP: $221.95Now: $178.00Was: $221.95 -
On Sale
PROX Piston Kit - 87.96 mm - Beta 350RR 01.7355.A
PROX
MSRP: $221.95Now: $178.00Was: $221.95When your Beta 350RR demands peak performance, a worn or suboptimal piston compromises both power delivery and engine longevity. The PROX Piston Kit delivers precision-engineered components that restore—or exceed—OEM efficiency while maintaining the...09106805- SKU:
- 09106805
- Availability:
- Ships Same Business Day
- Weight:
- 0.75 LBS
MSRP: $221.95Now: $178.00Was: $221.95 -
On Sale
PROX Piston Kit - 87.96 mm - Beta 390RR 01.7365.A
PROX
MSRP: $221.95Now: $183.00Was: $221.95A piston kit is the heart of your engine's combustion cycle—worn or damaged pistons directly compromise compression, power output, and engine longevity. The PROX 87.96 mm kit for the Beta 390RR delivers OEM-quality components engineered to exact...09106806- SKU:
- 09106806
- Availability:
- Ships Same Business Day
- Weight:
- 0.45 LBS
MSRP: $221.95Now: $183.00Was: $221.95 -
On Sale
PROX Piston Kit - 94.95 mm - Beta 400RR 01.7411.A
PROX
MSRP: $216.95Now: $183.00Was: $216.95A worn or damaged piston directly compromises engine compression, throttle response, and reliability—especially critical in a high-revving 400cc dirt bike where every fraction of performance matters. The PROX Piston Kit delivers OEM-grade precision at...09106808- SKU:
- 09106808
- Availability:
- Ships Same Business Day
- Weight:
- 0.60 LBS
MSRP: $216.95Now: $183.00Was: $216.95 -
On Sale
PROX Piston Kit - 94.95 mm - Beta 450RR 01.7412.A
PROX
MSRP: $221.95Now: $183.00Was: $221.95Your Beta 450RR's engine demands precision at every combustion cycle—and that starts with a piston kit engineered to exact OEM specifications. The PROX 94.95 mm kit delivers the durability and reliability you need for consistent power delivery, whether...09106809- SKU:
- 09106809
- Availability:
- Ships Same Business Day
- Weight:
- 0.85 LBS
MSRP: $221.95Now: $183.00Was: $221.95 -
On Sale
PROX Piston Kit - 94.96 mm - Beta 430RR 01.7415.A
PROX
MSRP: $216.95Now: $183.00Was: $216.95A worn or damaged piston directly compromises engine compression, throttle response, and overall reliability—especially critical in high-performance 430RR applications where precision tolerances are non-negotiable. This PROX Piston Kit delivers...09106811- SKU:
- 09106811
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 LBS
MSRP: $216.95Now: $183.00Was: $216.95 -
On Sale
PROX Piston Kit - 99.96 mm - Beta 480RR 01.7425.A
PROX
MSRP: $221.95Now: $183.00Was: $221.95A worn or damaged piston directly impacts engine compression, throttle response, and reliability—especially critical in high-revving two-stroke applications like the Beta 480RR. This PROX piston kit delivers OEM-quality precision with a complete...09106812- SKU:
- 09106812
- Availability:
- Ships Same Business Day
- Weight:
- 0.85 LBS
MSRP: $221.95Now: $183.00Was: $221.95 -
On Sale
PROX Piston Kit - 99.95 mm - Beta 498RR/520RR 01.7512.A
PROX
MSRP: $221.95Now: $183.00Was: $221.95The piston is the heart of your engine's combustion cycle, and worn or damaged pistons will kill performance and reliability. This PROX kit gives you OEM-quality components precision-engineered for your Beta 498RR/520RR, ensuring proper ring sealing,...09106813- SKU:
- 09106813
- Availability:
- Ships Same Business Day
- Weight:
- 0.95 LBS
MSRP: $221.95Now: $183.00Was: $221.95
