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 01.1342.C
PROX
$185.95When your engine demands precision and reliability, factory-original performance isn't negotiable. The PROX Piston Kit 01.1342.C delivers OEM-equivalent durability through meticulous Japanese manufacturing and high-silicon aluminum construction, ensuring...09030815- SKU:
- 09030815
- Availability:
- Ships Same Business Day
- Weight:
- 0.52 LBS
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 76.80 MM
- COMPRESSION RATIO IMPERIAL:
- 13.2:1
- ENGINE TYPE:
- 4-STROKE
- PRODUCT NAME:
- PISTON KIT
- TYPE:
- TOP END
- PISTON SIZE METRIC:
- STANDARD SIZE A
$185.95Qty in Cart: 0Quantity:Price:$185.95Subtotal: -
PROX Piston Kit 01.1342.B
PROX
$185.95Worn or damaged pistons compromise combustion efficiency, reduce power output, and risk catastrophic engine failure. The PROX Piston Kit 01.1342.B delivers OEM-equivalent performance with precision manufacturing that restores your engine to factory...09030816- SKU:
- 09030816
- Availability:
- Ships Same Business Day
- Weight:
- 0.51 LBS
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PRODUCT NAME:
- PISTON KIT
- TYPE:
- TOP END
- COMPRESSION RATIO IMPERIAL:
- 13.2:1
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 76.80 MM
$185.95 -
PROX Piston Kit 01.1414.C
PROX
$195.95A worn or damaged piston kit will compromise engine efficiency, increase blow-by, and risk catastrophic engine failure. The PROX Piston Kit 01.1414.C delivers OEM-grade replacement performance with precision-engineered tolerances and high-silicon...09030819- SKU:
- 09030819
- Availability:
- Ships Same Business Day
- Weight:
- 0.88 LBS
- BORE SIZE METRIC:
- 96.00 MM
- PRODUCT NAME:
- PISTON KIT
- COMPRESSION RATIO IMPERIAL:
- 12.0:1
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
- UNITS:
- EACH
- ENGINE TYPE:
- 4-STROKE
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- TOP END
$195.95 -
PROX Piston Kit 01.1411.B
PROX
$195.95When your engine's pistons are worn or damaged, you're losing compression, efficiency, and power—and risking catastrophic failure. The PROX Piston Kit 01.1411.B delivers OEM-equivalent performance with precision manufacturing that ensures reliable...09030823- SKU:
- 09030823
- Availability:
- Ships Same Business Day
- Weight:
- 0.79 LBS
- ENGINE TYPE:
- 4-STROKE
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PRODUCT NAME:
- PISTON KIT
- TYPE:
- TOP END
- BORE SIZE METRIC:
- 95.97 MM
- RIDING STYLE:
- OFF-ROAD
- COMPRESSION RATIO IMPERIAL:
- 12.0:1
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
$195.95Qty in Cart: 0Quantity:Price:$195.95Subtotal: -
PROX Piston Kit 01.2114.C
PROX
$99.95When your engine's pistons wear beyond safe operating limits, you're facing compromised compression, oil blow-by, and potential catastrophic failure. The PROX Piston Kit 01.2114.C delivers OEM-equivalent performance with the precision engineering of...09030828- SKU:
- 09030828
- Availability:
- Ships Same Business Day
- Weight:
- 0.32 LBS
- BORE SIZE METRIC:
- 47.50 MM
- PISTON SIZE METRIC:
- STANDARD SIZE C
- PRODUCT NAME:
- PISTON KIT
- ENGINE TYPE:
- 2-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- TYPE:
- TOP END
- UNITS:
- EACH
$99.95 -
PROX Piston Kit 01.2429.C
PROX
$195.95Your engine's heart demands precision engineering and materials that can withstand extreme combustion pressures cycle after cycle. The PROX Piston Kit 01.2429.C delivers exactly that—OEM-equivalent performance with the reliability of a...09030829- SKU:
- 09030829
- Availability:
- Ships Same Business Day
- Weight:
- 0.88 LBS
- COMPRESSION RATIO IMPERIAL:
- 12.5:1
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 95.00 MM
- PISTON SIZE METRIC:
- STANDARD SIZE C
- RIDING STYLE:
- OFF-ROAD
- ENGINE TYPE:
- 4-STROKE
- PISTON MATERIAL:
- ALUMINUM ALLOY
- TYPE:
- TOP END
- UNITS:
- EACH
$195.95 -
PROX Piston Kit 01.4121.C
PROX
$89.95A piston kit is the heart of engine reliability and performance—worn or damaged pistons directly compromise compression, power delivery, and engine longevity. The PROX Piston Kit 01.4121.C delivers OEM-equivalent quality at a fraction of the cost,...09030830- SKU:
- 09030830
- Availability:
- Ships Same Business Day
- Weight:
- 0.33 LBS
- BORE SIZE METRIC:
- 48.50 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
- UNITS:
- EACH
- ENGINE TYPE:
- 2-STROKE
- PRODUCT NAME:
- PISTON KIT
- TYPE:
- TOP END
$89.95Qty in Cart: 0Quantity:Price:$89.95Subtotal: -
On Sale
PROX Piston Kit 01.1323.A
PROX
MSRP: $143.95Now: $119.00Was: $143.95When your engine's pistons show signs of wear or damage, replacement isn't optional—it's essential for maintaining compression, preventing catastrophic failure, and preserving your engine's performance envelope. The PROX Piston Kit 01.1323.A delivers...PX1322A- SKU:
- PX1322A
- Availability:
- Ships Same Business Day
- Weight:
- 0.70 LBS
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 66.34 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 66.34 MM
- ENGINE TYPE:
- 2-STROKE
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
MSRP: $143.95Now: $119.00Was: $143.95 -
On Sale
PROX Piston Kit 01.1323.B
PROX
MSRP: $139.95Now: $119.00Was: $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 construction that matches or exceeds factory...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
MSRP: $139.95Now: $119.00Was: $139.95 -
On Sale
PROX Piston Kit 01.2114.A
PROX
MSRP: $99.95Now: $76.00Was: $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 delivers OEM-matched performance with the precision...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
MSRP: $99.95Now: $76.00Was: $99.95 -
On Sale
PROX Piston Kit 01.2114.B
PROX
MSRP: $99.95Now: $76.00Was: $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 OEM-equivalent durability with precision engineering,...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
MSRP: $99.95Now: $76.00Was: $99.95 -
On Sale
PROX Piston Kit 01.2224.A
PROX
MSRP: $121.95Now: $90.00Was: $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 precision engineering and material quality required for...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
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.2224.B
PROX
MSRP: $121.95Now: $90.00Was: $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 Japan to exact tolerances that keep your engine running at...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
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.1408.000
PROX
MSRP: $185.95Now: $158.00Was: $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 specifications with precision-engineered components...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
MSRP: $185.95Now: $158.00Was: $185.95 -
On Sale
PROX Piston Kit 01.1408.025
PROX
MSRP: $185.95Now: $158.00Was: $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 precision-engineered components manufactured to exacting tolerances in...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
MSRP: $185.95Now: $158.00Was: $185.95Qty in Cart: 0Quantity:Price:MSRP: $185.95Now: $158.00Was: $185.95Subtotal: -
On Sale
PROX Piston Kit 01.1408.050
PROX
MSRP: $185.95Now: $158.00Was: $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 delivers OEM-equivalent engineering with Japanese...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
MSRP: $185.95Now: $158.00Was: $185.95 -
On Sale
PROX Piston Kit 01.1408.075
PROX
MSRP: $185.95Now: $158.00Was: $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 restore your engine's compression integrity and thermal...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
MSRP: $185.95Now: $158.00Was: $185.95Qty in Cart: 0Quantity:Price:MSRP: $185.95Now: $158.00Was: $185.95Subtotal: -
On Sale
PROX Piston Kit 01.1408.100
PROX
MSRP: $199.95Now: $158.00Was: $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 CNC-machined precision, restoring your engine to...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
MSRP: $199.95Now: $158.00Was: $199.95 -
On Sale
PROX Piston Kit 01.1408.125
PROX
MSRP: $185.95Now: $158.00Was: $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 expertise and high-silicon aluminum construction that...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
MSRP: $185.95Now: $158.00Was: $185.95 -
On Sale
PROX Piston Kit 01.4221.A
PROX
MSRP: $105.95Now: $90.00Was: $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, this kit delivers the durability and tolerances you...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
MSRP: $105.95Now: $90.00Was: $105.95Qty in Cart: 0Quantity:Price:MSRP: $105.95Now: $90.00Was: $105.95Subtotal:
