Dirt Bike Piston and Ring Kits
Dirt Bike Piston & Ring Kits for Yamaha YZ85, WR250 & YZ250 at JJ Motorsports
Rebuild your dirt bike's top end for maximum power and reliability with premium piston and ring kits from JJ Motorsports, forged from high-strength aluminum for superior heat resistance, lightweight performance, and precise fit in motocross, enduro, and trail riding. Our selection includes complete kits with pistons, high-performance rings, wrist pins, circlips, top-end bearings, and gaskets designed for enhanced combustion efficiency, reduced blow-by, and longer engine life under high-RPM abuse. Compatible with popular models like Yamaha YZ85 (2002-2018), WR250, and YZ250, these Wiseco-engineered components feature CNC-machined crowns for optimal cam shape, ArmorGlide skirt coatings for low friction, and 4032 alloy construction for durability in dusty, aggressive conditions. Whether you're refreshing a youth 85cc 2-stroke or upgrading a 250cc big bore, these kits ensure crisp throttle response, better sealing, and race-ready power without the need for custom boring—perfect for DIY rebuilds or pro-level maintenance.
Shop trusted brands like Wiseco for race-proven quality. Explore related categories such as dirt bike engine for cylinders and valves or dirt bike air and fuel for carburetors and jets.
Top Dirt Bike Piston & Ring Kits
- Wiseco YZ85 2002-2018 Piston Kit with Gaskets PK1202 – 47.50mm forged aluminum piston kit for Yamaha YZ85 2-stroke; includes rings, wrist pin, circlips, bearing, and gaskets for enhanced combustion and throttle response.
- Wiseco 68.00mm Piston Kit with Gaskets Yamaha WR/YZ 250 PK1563 – Complete big bore kit for Yamaha WR250/YZ250; features forged piston, rings, wrist pin, circlips, and top-end gaskets for superior power and sealing.
Browse our in-stock inventory below with same-day shipping and expert support. Free shipping on orders over $99! Questions? Contact us for fitment advice!
- Product
- Qty in Cart
- Quantity
- Price
- Subtotal
-
PROX Piston Kit 01.1225.C
PROX
$105.95Whether you're rebuilding a tired engine or replacing worn components after high-mileage use, the PROX Piston Kit 01.1225.C delivers OEM-spec reliability with precision engineering that ensures consistent performance and longevity. Cast from...09100599- SKU:
- 09100599
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- PISTON DIAMETER METRIC:
- 53.96 MM
- UNITS:
- EACH
- BORE SIZE METRIC:
- 53.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
- PRODUCT NAME:
- PISTON KIT
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
$105.95Qty in Cart: 0Quantity:Price:$105.95Subtotal: -
PROX Piston Kit 01.4325.B
PROX
$139.95When your engine's pistons show wear or damage, you're facing power loss, compression issues, and potential catastrophic failure. The PROX Piston Kit 01.4325.B delivers OEM-quality replacement pistons engineered to restore your engine's original...09100600- SKU:
- 09100600
- Availability:
- Ships Same Business Day
- Weight:
- 0.75 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 66.35 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PISTON DIAMETER METRIC:
- 66.35 MM
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
$139.95Qty in Cart: 0Quantity:Price:$139.95Subtotal: -
PROX Piston Kit 01.1414.B
PROX
$210.95A piston kit is fundamental to engine reliability and performance—wear or damage compromises compression, efficiency, and power delivery. The PROX Piston Kit 01.1414.B delivers OEM-grade quality with precision engineering, ensuring your engine maintains...09100608- SKU:
- 09100608
- Availability:
- Ships Same Business Day
- Weight:
- 0.82 LBS
- PISTON DIAMETER METRIC:
- 95.97 MM
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 95.97 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$210.95 -
PROX Piston Kit 01.1075.000
PROX
$77.95A piston kit is the heart of your engine's combustion cycle—when yours are worn, scored, or damaged, you lose compression, power, and reliability. The PROX Piston Kit 01.1075.000 restores your engine to OEM-specification performance with...09100399- SKU:
- 09100399
- Availability:
- Ships Same Business Day
- Weight:
- 0.19 LBS
- RIDING STYLE:
- OFF-ROAD
- ENGINE TYPE:
- 4-STROKE
- PISTON DIAMETER METRIC:
- 47.00 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 47.00 MM
$77.95 -
PROX Piston Kit 01.1075.050
PROX
$77.95When your engine demands precision and reliability, OEM-equivalent pistons are non-negotiable. The PROX Piston Kit 01.1075.050 delivers factory-spec performance with Japanese manufacturing precision, ensuring consistent combustion chamber geometry and...09100400- SKU:
- 09100400
- Availability:
- Ships Same Business Day
- Weight:
- 0.27 LBS
- PISTON DIAMETER METRIC:
- 47.50 MM
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE IMPERIAL:
- +0.020'
- BORE SIZE METRIC:
- 47.50 MM
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$77.95 -
PROX Piston Kit 01.1075.100
PROX
$59.95Worn or damaged pistons compromise engine efficiency, reduce horsepower, and accelerate wear on surrounding components. The PROX Piston Kit 01.1075.100 delivers OEM-equivalent performance with precision manufacturing, restoring your engine to factory...09100401- SKU:
- 09100401
- Availability:
- Ships Same Business Day
- Weight:
- 0.27 LBS
- BORE SIZE METRIC:
- 48.00 MM
- PRODUCT NAME:
- PISTON KIT
- ENGINE TYPE:
- 4-STROKE
- PISTON DIAMETER METRIC:
- 48.00 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE IMPERIAL:
- +0.040'
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$59.95 -
PROX Piston Kit 01.1403.A
PROX
$195.95Your engine's pistons are the workhorses converting combustion into power—wear them out, and you lose compression, efficiency, and reliability. The PROX Piston Kit 01.1403.A delivers OEM-equivalent performance with precision manufacturing and premium...09100418- SKU:
- 09100418
- Availability:
- Ships Same Business Day
- Weight:
- 0.56 LBS
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 95.96 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- BORE SIZE METRIC:
- 95.96 MM
- RIDING STYLE:
- OFF-ROAD
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$195.95Qty in Cart: 0Quantity:Price:$195.95Subtotal: -
PROX Piston Kit 01.1403.B
PROX
$195.95A piston kit is the heart of your engine's combustion cycle—wear or damage here directly impacts power delivery, fuel efficiency, and engine longevity. The PROX Piston Kit 01.1403.B delivers OEM-equivalent performance with precision manufacturing that...09100419- SKU:
- 09100419
- Availability:
- Ships Same Business Day
- Weight:
- 0.81 LBS
- BORE SIZE METRIC:
- 95.97 MM
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 95.97 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$195.95Qty in Cart: 0Quantity:Price:$195.95Subtotal: -
PROX Piston Kit 01.4335.A
PROX
$179.95Worn or damaged pistons compromise engine compression, efficiency, and reliability—leading to power loss, increased fuel consumption, and potential catastrophic failure. The PROX Piston Kit 01.4335.A delivers OEM-spec performance with precision...09100425- SKU:
- 09100425
- Availability:
- Ships Same Business Day
- Weight:
- 0.85 LBS
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 76.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 76.96 MM
$179.95Qty in Cart: 0Quantity:Price:$179.95Subtotal: -
PROX Piston Kit 01.4335.B
PROX
$188.95Factory piston performance starts with precision engineering—and the PROX Piston Kit 01.4335.B delivers exactly that. Built to OEM specifications using high-silicon aluminum alloy, this Japanese-manufactured kit ensures reliable power delivery and...09100426- SKU:
- 09100426
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- PISTON DIAMETER METRIC:
- 76.97 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE B
- UNITS:
- EACH
- BORE SIZE METRIC:
- 76.97 MM
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- PISTON KIT
$188.95 -
PROX Piston Kit 01.4335.C
PROX
$179.95Factory piston wear compromises compression, ring seal, and combustion efficiency—leading to power loss, increased blowby, and accelerated engine degradation. The PROX Piston Kit 01.4335.C restores OEM performance specifications with Japanese...09100427- SKU:
- 09100427
- Availability:
- Ships Same Business Day
- Weight:
- 0.56 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
- UNITS:
- EACH
- BORE SIZE METRIC:
- 76.98 MM
- PISTON DIAMETER METRIC:
- 76.98 MM
- RIDING STYLE:
- OFF-ROAD
- PRODUCT NAME:
- PISTON KIT
$179.95Qty in Cart: 0Quantity:Price:$179.95Subtotal: -
PROX Piston Kit 01.1222.A
PROX
$132.95A piston kit is one of the most critical components in engine performance and longevity. The PROX Piston Kit 01.1222.A delivers OEM-equivalent reliability with the precision engineering that high-performance engines demand. Whether you're rebuilding...09100428- SKU:
- 09100428
- Availability:
- Ships Same Business Day
- Weight:
- 0.41 LBS
- BORE SIZE METRIC:
- 53.94 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- ENGINE TYPE:
- 2-STROKE
- PISTON DIAMETER METRIC:
- 53.94 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
$132.95 -
PROX Piston Kit 01.1222.B
PROX
$105.95If your engine is showing signs of wear—loss of compression, increased blow-by, or worn ring grooves—a quality piston kit is your most direct path to restored performance and reliability. The PROX Piston Kit 01.1222.B delivers OEM-equivalent engineering...09100429- SKU:
- 09100429
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 53.95 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON DIAMETER METRIC:
- 53.95 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE B
- UNITS:
- EACH
- PRODUCT NAME:
- PISTON KIT
$105.95 -
PROX Piston Kit 01.3122.A
PROX
$99.95When your engine is running at the edge of performance, factory pistons become a liability. The PROX Piston Kit 01.3122.A delivers OEM-equivalent reliability with precision manufacturing that keeps your engine balanced and efficient through sustained...09100431- SKU:
- 09100431
- Availability:
- Ships Same Business Day
- Weight:
- 0.85 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 47.94 MM
- BORE SIZE METRIC:
- 47.94 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
$99.95 -
PROX Piston Kit 01.3122.B
PROX
$99.95A piston kit is the foundation of reliable engine performance—when factory pistons wear or fail, you need a direct OEM replacement that matches original specifications precisely. The PROX Piston Kit 01.3122.B delivers the exact geometry, material...09100432- SKU:
- 09100432
- Availability:
- Ships Same Business Day
- Weight:
- 0.41 LBS
- PISTON DIAMETER METRIC:
- 47.95 MM
- BORE SIZE METRIC:
- 47.95 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE B
- RIDING STYLE:
- OFF-ROAD
$99.95 -
PROX Piston Kit 01.3224.A
PROX
$105.95A worn or damaged piston compromises combustion efficiency, fuel economy, and overall engine reliability. The PROX Piston Kit 01.3224.A delivers OEM-equivalent performance with precision engineering, giving you the confidence to push your engine to its...09100434- SKU:
- 09100434
- Availability:
- Ships Same Business Day
- Weight:
- 0.85 LBS
- PISTON DIAMETER METRIC:
- 53.95 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 53.95 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
$105.95 -
PROX Piston Kit 01.3224.B
PROX
$101.95When your engine demands precision and reliability at high RPM, compromised pistons will cost you performance—and credibility. The PROX Piston Kit 01.3224.B delivers OEM-equivalent performance through Japanese engineering and CNC-machined accuracy,...09100435- SKU:
- 09100435
- Availability:
- Ships Same Business Day
- Weight:
- 0.41 LBS
- BORE SIZE METRIC:
- 53.96 MM
- PISTON DIAMETER METRIC:
- 53.96 MM
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$101.95Qty in Cart: 0Quantity:Price:$101.95Subtotal: -
PROX Piston Kit 01.3420.B
PROX
$185.95A piston kit is the heart of your engine's combustion cycle—worn or damaged pistons compromise compression, power delivery, and reliability. The PROX Piston Kit 01.3420.B delivers OEM-equivalent performance with the precision engineering of a Japanese...09100438- SKU:
- 09100438
- Availability:
- Ships Same Business Day
- Weight:
- 0.90 LBS
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$185.95 -
PROX Piston Kit 01.2429.A
PROX
$210.95A piston kit is the heart of reliable engine performance, and worn or damaged pistons compromise compression, power delivery, and fuel efficiency. The PROX Piston Kit 01.2429.A delivers OEM-equivalent quality with precision manufacturing, ensuring your...09100439- SKU:
- 09100439
- Availability:
- Ships Same Business Day
- Weight:
- 0.57 LBS
- BORE SIZE METRIC:
- 94.95 MM
- PISTON DIAMETER METRIC:
- 94.95 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$210.95 -
PROX Piston Kit 01.2429.B
PROX
$210.95A worn or damaged piston compromises combustion efficiency, reduces power output, and risks catastrophic engine failure. The PROX Piston Kit 01.2429.B delivers OEM-equivalent performance with precision engineering, restoring your engine to factory...09100440- SKU:
- 09100440
- Availability:
- Ships Same Business Day
- Weight:
- 0.82 LBS
- RIDING STYLE:
- OFF-ROAD
- ENGINE TYPE:
- 4-STROKE
- PISTON DIAMETER METRIC:
- 94.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE B
- UNITS:
- EACH
- BORE SIZE METRIC:
- 94.96 MM
- PRODUCT NAME:
- PISTON KIT
$210.95
