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
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PROX Piston Kit 01.1323.B
PROX
$139.95When your engine demands reliability under extreme conditions, OEM-spec pistons are non-negotiable. The PROX Piston Kit 01.1323.B delivers Japanese manufacturing precision and high-silicon aluminum...PX1322B- SKU:
- PX1322B
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 66.35 MM
- PISTON DIAMETER METRIC:
- 66.35 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
$139.95Qty in Cart: 0Quantity:Price:$139.95Subtotal: -
PROX Piston Kit 01.2114.A
PROX
$99.95Worn or damaged pistons compromise compression, reliability, and power output—making a quality replacement essential for any engine rebuild or high-mileage refresh. The PROX Piston Kit 01.2114.A...PX2112A- SKU:
- PX2112A
- Availability:
- Ships Same Business Day
- Weight:
- 0.32 LBS
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 47.44 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON DIAMETER METRIC:
- 47.44 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON SIZE METRIC:
- STANDARD SIZE A
$99.95 -
PROX Piston Kit 01.2114.B
PROX
$99.95Piston failure compromises engine reliability and performance—whether you're rebuilding after catastrophic wear or upgrading to factory-plus specifications. The PROX Piston Kit 01.2114.B delivers...PX2112B- SKU:
- PX2112B
- Availability:
- Ships Same Business Day
- Weight:
- 0.32 LBS
- ENGINE TYPE:
- 2-STROKE
- PISTON DIAMETER METRIC:
- 47.45 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 47.45 MM
- RIDING STYLE:
- OFF-ROAD
$99.95 -
PROX Piston Kit 01.2224.A
PROX
$121.95When your engine's stock pistons reach the end of their service life, you need a direct replacement that matches OEM specifications without compromise. The PROX Piston Kit 01.2224.A delivers the...PX2222A- SKU:
- PX2222A
- Availability:
- Ships Same Business Day
- Weight:
- 0.32 LBS
- PISTON DIAMETER METRIC:
- 53.94 MM
- RIDING STYLE:
- OFF-ROAD
- ENGINE TYPE:
- 2-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 53.94 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
$121.95 -
PROX Piston Kit 01.2224.B
PROX
$121.95When your engine demands reliability and precision, OEM-quality pistons are non-negotiable. The PROX Piston Kit 01.2224.B delivers factory-spec performance without factory downtime, engineered in...PX2222B- SKU:
- PX2222B
- Availability:
- Ships Same Business Day
- Weight:
- 0.32 LBS
- BORE SIZE METRIC:
- 53.95 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE B
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 53.95 MM
- PRODUCT NAME:
- PISTON KIT
$121.95 -
PROX Piston Kit 01.1408.000
PROX
$185.95A worn or damaged piston kit compromises combustion efficiency, increases blow-by, and can lead to catastrophic engine failure. The PROX Piston Kit 01.1408.000 restores your engine to OEM performance...PX4040- SKU:
- PX4040
- Availability:
- Ships Same Business Day
- Weight:
- 1.25 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD
- UNITS:
- EACH
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 89.00 MM
- PISTON DIAMETER METRIC:
- 89.00 MM
- PRODUCT NAME:
- PISTON KIT
$185.95 -
PROX Piston Kit 01.1408.025
PROX
$185.95When your engine's pistons show wear, you're losing compression, efficiency, and power. The PROX Piston Kit 01.1408.025 restores your engine to OEM performance specifications with...PX4041- SKU:
- PX4041
- Availability:
- Ships Same Business Day
- Weight:
- 1.25 LBS
- PISTON DIAMETER METRIC:
- 89.25 MM
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PISTON MATERIAL:
- ALUMINUM ALLOY
- BORE SIZE METRIC:
- 89.25 MM
- PISTON SIZE IMPERIAL:
- +0.010'
- PRODUCT NAME:
- PISTON KIT
$185.95Qty in Cart: 0Quantity:Price:$185.95Subtotal: -
PROX Piston Kit 01.1408.050
PROX
$185.95A piston kit is fundamental to engine reliability and performance—worn or damaged pistons compromise compression, increase blow-by, and accelerate engine wear. The PROX Piston Kit 01.1408.050...PX4042- SKU:
- PX4042
- Availability:
- Ships Same Business Day
- Weight:
- 1.26 LBS
- BORE SIZE METRIC:
- 89.50 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON SIZE METRIC:
- +0.50 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 89.50 MM
$185.95 -
PROX Piston Kit 01.1408.075
PROX
$185.95Your engine's heart demands precision and reliability—and the PROX Piston Kit 01.1408.075 delivers exactly that. Built to OEM specifications with Japanese manufacturing excellence, these pistons...PX4043- SKU:
- PX4043
- Availability:
- Ships Same Business Day
- Weight:
- 1.30 LBS
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 89.75 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 89.75 MM
- PISTON SIZE IMPERIAL:
- +0.030'
- PRODUCT NAME:
- PISTON KIT
$185.95Qty in Cart: 0Quantity:Price:$185.95Subtotal: -
PROX Piston Kit 01.1408.100
PROX
$199.95Worn or damaged pistons compromise combustion efficiency, reduce power output, and risk catastrophic engine failure. The PROX Piston Kit 01.1408.100 delivers OEM-specification performance with...PX4044- SKU:
- PX4044
- Availability:
- Ships Same Business Day
- Weight:
- 1.25 LBS
- BORE SIZE METRIC:
- 90.00 MM
- PISTON DIAMETER METRIC:
- 90.00 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- +1.00 MM
- UNITS:
- EACH
- ENGINE TYPE:
- 2-STROKE
- RIDING STYLE:
- OFF-ROAD
$199.95 -
PROX Piston Kit 01.1408.125
PROX
$185.95When your engine demands reliability and precision, OEM-equivalent performance is non-negotiable. The PROX Piston Kit 01.1408.125 delivers exact fitment and durability through Japanese manufacturing...PX4045- SKU:
- PX4045
- Availability:
- Ships Same Business Day
- Weight:
- 1.35 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 90.25 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON DIAMETER METRIC:
- 90.25 MM
- PISTON SIZE IMPERIAL:
- +0.050'
- RIDING STYLE:
- OFF-ROAD
$185.95 -
PROX Piston Kit 01.4221.A
PROX
$105.95Engine reliability starts with precision internal components—and PROX pistons are engineered to exacting OEM standards without compromise. If you're rebuilding an engine or replacing worn internals,...PX4221A- SKU:
- PX4221A
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- BORE SIZE METRIC:
- 53.96 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 53.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$105.95Qty in Cart: 0Quantity:Price:$105.95Subtotal: -
PROX Piston Kit 01.4221.B
PROX
$105.95Your engine's piston kit is the foundation of reliable power delivery and longevity under load. Factory pistons wear, lose compression, and compromise performance—the PROX Piston Kit 01.4221.B...PX4221B- SKU:
- PX4221B
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- PISTON DIAMETER METRIC:
- 53.97 MM
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 53.97 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON MATERIAL:
- ALUMINUM ALLOY
$105.95Qty in Cart: 0Quantity:Price:$105.95Subtotal: -
PROX Piston Kit 01.1208.A3
PROX
$105.95A worn or damaged piston kit compromises combustion efficiency, increases blow-by, and accelerates engine wear—ultimately costing you performance and reliability. The PROX Piston Kit 01.1208.A3...PX4240D- SKU:
- PX4240D
- Availability:
- Ships Same Business Day
- Weight:
- 0.38 LBS
- BORE SIZE METRIC:
- 53.97 MM
- PISTON DIAMETER METRIC:
- 53.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
$105.95Qty in Cart: 0Quantity:Price:$105.95Subtotal: -
PROX Piston Kit 01.1218.A1
PROX
$132.95A piston kit is the heart of engine reliability and performance—without proper pistons, you're risking catastrophic failure under boost or high RPM. The PROX Piston Kit 01.1218.A1 delivers OEM-grade...PX4260A- SKU:
- PX4260A
- Availability:
- Ships Same Business Day
- Weight:
- 0.38 LBS
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 53.94 MM
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 53.94 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$132.95 -
PROX Piston Kit 01.1218.A2
PROX
$132.95A worn or damaged piston directly compromises engine efficiency, compression, and longevity—especially under sustained high-RPM operation. The PROX Piston Kit 01.1218.A2 delivers OEM-equivalent...PX4260B- SKU:
- PX4260B
- Availability:
- Ships Same Business Day
- Weight:
- 0.38 LBS
- BORE SIZE METRIC:
- 53.95 MM
- PISTON DIAMETER METRIC:
- 53.95 MM
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
$132.95Qty in Cart: 0Quantity:Price:$132.95Subtotal: -
PROX Piston Kit 01.1218.A4
PROX
$132.95A piston kit is the backbone of engine reliability and performance—worn or damaged pistons lead to compression loss, increased blowby, and catastrophic engine failure. The PROX Piston Kit 01.1218.A4...PX4260D- SKU:
- PX4260D
- Availability:
- Ships Same Business Day
- Weight:
- 0.40 LBS
- PISTON DIAMETER METRIC:
- 53.97 MM
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 53.97 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE A
$132.95 -
PROX Piston Kit 01.4108.A
PROX
$93.95When your engine's internal components start to wear, piston degradation directly impacts compression, fuel efficiency, and overall power delivery. The PROX Piston Kit 01.4108.A is engineered as a...PX4280A- SKU:
- PX4280A
- Availability:
- Ships Same Business Day
- Weight:
- 0.30 LBS
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 47.94 MM
- BORE SIZE METRIC:
- 47.94 MM
- RIDING STYLE:
- OFF-ROAD
$93.95Qty in Cart: 0Quantity:Price:$93.95Subtotal: -
PROX Piston Kit 01.4108.C
PROX
$89.95When your engine demands precision and reliability, stock pistons won't cut it. The PROX Piston Kit 01.4108.C delivers OEM-equivalent performance with the tight tolerances and material integrity your...PX4280C- SKU:
- PX4280C
- Availability:
- Ships Same Business Day
- Weight:
- 0.30 LBS
- PISTON DIAMETER METRIC:
- 47.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- BORE SIZE METRIC:
- 47.96 MM
- PRODUCT NAME:
- PISTON KIT
$89.95Qty in Cart: 0Quantity:Price:$89.95Subtotal: -
PROX Piston Kit 01.4121.A
PROX
$99.95Factory pistons wear out or fail, leaving you with expensive downtime and compromised engine performance. The PROX Piston Kit 01.4121.A delivers OEM-equivalent quality at a fraction of the cost,...PX4281A- SKU:
- PX4281A
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 48.45 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 48.45 MM
- RIDING STYLE:
- OFF-ROAD
$99.95
