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
-
On Sale
PROX Piston Kit 01.4221.B
PROX
MSRP: $105.95Now: $90.00Was: $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 restores OEM-specification durability with...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
MSRP: $105.95Now: $90.00Was: $105.95Qty in Cart: 0Quantity:Price:MSRP: $105.95Now: $90.00Was: $105.95Subtotal: -
On Sale
PROX Piston Kit 01.1208.A3
PROX
MSRP: $105.95Now: $90.00Was: $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 restores your engine to OEM specifications with...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
MSRP: $105.95Now: $90.00Was: $105.95Qty in Cart: 0Quantity:Price:MSRP: $105.95Now: $90.00Was: $105.95Subtotal: -
On Sale
PROX Piston Kit 01.1218.A1
PROX
MSRP: $132.95Now: $90.00Was: $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 construction with precision engineering, ensuring your...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
MSRP: $132.95Now: $90.00Was: $132.95 -
On Sale
PROX Piston Kit 01.1218.A2
PROX
MSRP: $132.95Now: $90.00Was: $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 performance with precision engineering, ensuring reliable...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
MSRP: $132.95Now: $90.00Was: $132.95 -
On Sale
PROX Piston Kit 01.1218.A4
PROX
MSRP: $132.95Now: $90.00Was: $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 delivers OEM-equivalent quality with precision...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
MSRP: $132.95Now: $90.00Was: $132.95 -
On Sale
PROX Piston Kit 01.4108.A
PROX
MSRP: $93.95Now: $76.00Was: $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 direct OEM replacement, offering the precision and...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
MSRP: $93.95Now: $76.00Was: $93.95Qty in Cart: 0Quantity:Price:MSRP: $93.95Now: $76.00Was: $93.95Subtotal: -
On Sale
PROX Piston Kit 01.4108.C
PROX
MSRP: $89.95Now: $76.00Was: $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 high-revving builds require. This complete kit...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
MSRP: $89.95Now: $76.00Was: $89.95Qty in Cart: 0Quantity:Price:MSRP: $89.95Now: $76.00Was: $89.95Subtotal: -
On Sale
PROX Piston Kit 01.4121.A
PROX
MSRP: $99.95Now: $76.00Was: $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, engineered in Japan with the same exacting standards as...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
MSRP: $99.95Now: $76.00Was: $99.95 -
On Sale
PROX Piston Kit 01.4121.B
PROX
MSRP: $99.95Now: $76.00Was: $99.95When your engine demands reliability at high RPM, OEM-equivalent pistons aren't optional—they're essential. The PROX Piston Kit 01.4121.B delivers factory-spec performance with the precision engineering required for competitive racing and serious street...PX4281B- SKU:
- PX4281B
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- PISTON DIAMETER METRIC:
- 48.46 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- BORE SIZE METRIC:
- 48.46 MM
- PISTON SIZE METRIC:
- STANDARD SIZE B
- PRODUCT NAME:
- PISTON KIT
- RIDING STYLE:
- OFF-ROAD
MSRP: $99.95Now: $76.00Was: $99.95 -
On Sale
PROX Piston Kit 01.4100.B
PROX
MSRP: $79.95Now: $68.00Was: $79.95When your engine demands precision and reliability, OEM-quality pistons are non-negotiable. The PROX Piston Kit 01.4100.B delivers factory-spec performance with Japanese engineering and CNC precision, ensuring consistent compression, thermal stability,...PX4290A- SKU:
- PX4290A
- Availability:
- Ships Same Business Day
- Weight:
- 0.25 LBS
- PISTON DIAMETER METRIC:
- 42.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 42.96 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- RIDING STYLE:
- OFF-ROAD
MSRP: $79.95Now: $68.00Was: $79.95Qty in Cart: 0Quantity:Price:MSRP: $79.95Now: $68.00Was: $79.95Subtotal: -
On Sale
PROX Piston Kit 01.4216.A
PROX
MSRP: $105.95Now: $90.00Was: $105.95When your engine's pistons wear beyond safe limits, you're looking at catastrophic failure and a complete rebuild. The PROX Piston Kit 01.4216.A restores your engine to OEM-specification performance with precision-engineered components that handle the...PX4296A- SKU:
- PX4296A
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- BORE SIZE METRIC:
- 53.95 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PISTON DIAMETER METRIC:
- 53.95 MM
- PRODUCT NAME:
- PISTON KIT
MSRP: $105.95Now: $90.00Was: $105.95Qty in Cart: 0Quantity:Price:MSRP: $105.95Now: $90.00Was: $105.95Subtotal: -
On Sale
PROX Piston Kit 01.4216.B
PROX
MSRP: $121.95Now: $90.00Was: $121.95A worn or damaged piston compromises combustion efficiency, reduces power output, and can lead to catastrophic engine failure. The PROX Piston Kit 01.4216.B delivers OEM-level reliability with precision engineering, restoring your engine to factory...PX4296B- SKU:
- PX4296B
- Availability:
- Ships Same Business Day
- Weight:
- 0.38 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE B
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 53.96 MM
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 53.96 MM
- PRODUCT NAME:
- PISTON KIT
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.4216.C
PROX
MSRP: $105.95Now: $90.00Was: $105.95When you're rebuilding an engine or replacing worn pistons, you need a drop-in solution that matches OEM performance without compromise. The PROX Piston Kit 01.4216.C delivers exactly that—factory-spec reliability with Japanese manufacturing precision...PX4296C- SKU:
- PX4296C
- Availability:
- Ships Same Business Day
- Weight:
- 0.38 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 53.97 MM
- BORE SIZE METRIC:
- 53.97 MM
- PISTON SIZE METRIC:
- STANDARD SIZE C
- PRODUCT NAME:
- PISTON KIT
MSRP: $105.95Now: $90.00Was: $105.95 -
On Sale
PROX Piston Kit 01.4218.A
PROX
MSRP: $121.95Now: $90.00Was: $121.95A piston kit is the heart of your engine's combustion cycle—worn or damaged pistons directly compromise compression, power delivery, and engine longevity. The PROX Piston Kit 01.4218.A delivers OEM-equivalent performance with precision manufacturing that...PX4299A- SKU:
- PX4299A
- Availability:
- Ships Same Business Day
- Weight:
- 0.50 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: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.4218.C
PROX
MSRP: $121.95Now: $90.00Was: $121.95Your engine's power delivery and longevity depend on piston quality—and factory replacements often compromise on durability or precision. The PROX Piston Kit 01.4218.C delivers OEM-equivalent performance with Japanese manufacturing standards and...PX4299C- SKU:
- PX4299C
- Availability:
- Ships Same Business Day
- Weight:
- 0.42 LBS
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 53.98 MM
- PISTON SIZE METRIC:
- STANDARD SIZE C
- RIDING STYLE:
- OFF-ROAD
- PISTON DIAMETER METRIC:
- 53.98 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
MSRP: $121.95Now: $90.00Was: $121.95 -
On Sale
PROX Piston Kit 01.4322.B
PROX
MSRP: $143.95Now: $119.00Was: $143.95A worn or damaged piston compromises combustion efficiency, power delivery, and engine longevity. The PROX Piston Kit 01.4322.B restores OEM-level performance with precision-engineered components manufactured to exacting tolerances in Japan. This...PX4308B- SKU:
- PX4308B
- Availability:
- Ships Same Business Day
- Weight:
- 0.75 LBS
- PISTON DIAMETER METRIC:
- 66.35 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PRODUCT NAME:
- PISTON KIT
- BORE SIZE METRIC:
- 66.35 MM
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE B
- RIDING STYLE:
- OFF-ROAD
MSRP: $143.95Now: $119.00Was: $143.95 -
On Sale
PROX Piston Kit 01.4322.C
PROX
MSRP: $143.95Now: $119.00Was: $143.95A piston kit is the heart of your engine's combustion chamber—when yours shows wear, blow-by, or loss of compression, replacement becomes non-negotiable for reliable performance. The PROX Piston Kit 01.4322.C delivers OEM-equivalent engineering with...PX4308C- SKU:
- PX4308C
- Availability:
- Ships Same Business Day
- Weight:
- 0.75 LBS
- PISTON DIAMETER METRIC:
- 66.36 MM
- PISTON SIZE METRIC:
- STANDARD SIZE C
- PRODUCT NAME:
- PISTON KIT
- UNITS:
- EACH
- BORE SIZE METRIC:
- 66.36 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- RIDING STYLE:
- OFF-ROAD
MSRP: $143.95Now: $119.00Was: $143.95 -
On Sale
PROX Piston Kit 01.4285.A
PROX
MSRP: $132.95Now: $110.00Was: $132.95When your engine's factory pistons show wear or you're rebuilding after high-mileage use, settling for inferior replacements compromises reliability and performance. The PROX Piston Kit 01.4285.A delivers OEM-equivalent durability with precision...PX4310A- SKU:
- PX4310A
- Availability:
- Ships Same Business Day
- Weight:
- 0.55 LBS
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON DIAMETER METRIC:
- 65.94 MM
- RIDING STYLE:
- OFF-ROAD
- BORE SIZE METRIC:
- 65.94 MM
- PISTON SIZE METRIC:
- STANDARD SIZE A
- PRODUCT NAME:
- PISTON KIT
MSRP: $132.95Now: $110.00Was: $132.95 -
On Sale
PROX Piston Kit 01.4285.B
PROX
MSRP: $132.95Now: $110.00Was: $132.95When your engine's internals are worn or damaged, a quality piston kit is non-negotiable for restoring reliable power and compression. The PROX Piston Kit 01.4285.B delivers OEM-grade performance without the OEM price tag, engineered to exact factory...PX4310B- SKU:
- PX4310B
- Availability:
- Ships Same Business Day
- Weight:
- 0.60 LBS
- PISTON DIAMETER METRIC:
- 65.95 MM
- RIDING STYLE:
- OFF-ROAD
- PISTON MATERIAL:
- ALUMINUM ALLOY
- UNITS:
- EACH
- PISTON SIZE METRIC:
- STANDARD SIZE B
- BORE SIZE METRIC:
- 65.95 MM
- PRODUCT NAME:
- PISTON KIT
MSRP: $132.95Now: $110.00Was: $132.95 -
On Sale
PROX Piston Kit 01.4285.C
PROX
MSRP: $132.95Now: $110.00Was: $132.95A piston kit is fundamental to engine reliability and performance—worn or damaged pistons compromise combustion efficiency, increase blow-by, and risk catastrophic engine failure. The PROX Piston Kit 01.4285.C delivers OEM-equivalent quality at a...PX4310C- SKU:
- PX4310C
- Availability:
- Ships Same Business Day
- Weight:
- 0.65 LBS
- RIDING STYLE:
- OFF-ROAD
- UNITS:
- EACH
- PRODUCT NAME:
- PISTON KIT
- PISTON DIAMETER METRIC:
- 65.96 MM
- BORE SIZE METRIC:
- 65.96 MM
- PISTON MATERIAL:
- ALUMINUM ALLOY
- PISTON SIZE METRIC:
- STANDARD SIZE C
MSRP: $132.95Now: $110.00Was: $132.95
