Wiseco GP Series Piston Kit with Gaskets - Yamaha YZ125 / YZ125X (2005-2022) - 58.00mm Bore (+4.00mm BIG BORE) - 144cc - 2-Stroke Race-Spec
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Wiseco GP Series Piston Kit with Gaskets - Yamaha YZ125 / YZ125X - MAXIMUM BIG BORE
The Wiseco GP Series represents the pinnacle of 2-stroke piston technology for the legendary Yamaha YZ125. This is the MAXIMUM BIG BORE kit (+4.00mm) that increases displacement from 125cc to a massive 144cc - giving your YZ125 extreme power gains with GP Series race-spec features!
š„ MAXIMUM BIG BORE: 125cc ā 144cc (+15.2%!)
This +4.00mm big bore kit provides a massive 19cc displacement increase - that's 15.2% more displacement for significantly improved power throughout the rev range! This is the largest bore available for the YZ125 platform.
ā ļø Important: Installation Requirements
Crankcase clearance is required. The larger piston diameter may require crankcase modification for proper clearance.
š GP Series Race-Spec Features
- Electra Coating - Crown, ring groove(s), and pin bores coated for maximum wear resistance
- ArmorGlideĀ® Skirt Coating - Protection from micro-welding, galling, and detonation
- Extra Lightening Operations - Enhanced throttle response
- Made in USA - Engineered, forged, and machined in the USA
Kit Includes
- Wiseco GP Series Piston - Premium 4032 aluminum alloy with Electra + ArmorGlideĀ®
- Ring Set
- Wrist Pin
- Circlips
- Wrist Pin Bearing
- Top End Gasket Set
Key Features
- GP Series design for professional-level racing performance
- 4032 aluminum alloy construction - optimized for 2-stroke applications
- Dual coating system - Electra + ArmorGlideĀ® for ultimate protection
- Designed for endurance and sustained RPM riding
- Complete top-end gasket kit included
- Wrist pin bearing included - everything for a complete rebuild
Displacement Comparison
- Stock Bore: 54.00mm = 125cc
- +2.00mm Bore: 56.00mm = 134cc
- +4.00mm Bore: 58.00mm = 144cc (MAXIMUM!)
Important Notes
- Crankcase clearance required
- Cylinder must be bored to 58.00mm
- Wiseco ring types are not interchangeable
- Wiseco pistons can be fitted only with Wiseco rings
- Cylinder sleeves must be purchased separately if needed
Piston Specifications
- Bore Size: 58.00 mm (+4.00mm Big Bore)
- Piston Diameter: 57.95 mm
- Stroke Length: 54.50 mm
- Material: 4032 Aluminum Alloy
- Skirt Coating: ArmorGlideĀ® + Electra
- Style: GP Series
Engine Specifications
- Displacement: 144cc (up from 125cc)
- Engine Type: 2-Stroke
- Weight: 0.9 lbs
Fitment
Yamaha:
- YZ125: 2005-2021 (17 years!)
- YZ125X: 2020-2022 (enduro variant)
Why Choose the 58mm Maximum Big Bore?
For riders who want the absolute maximum displacement from their YZ125, this 144cc conversion combined with GP Series race technology delivers unmatched power. Popular for open class racing and riders who want every possible advantage!
š¦ Shipping Information
In-stock items ship next business day. ModQuad parts dispatch Monday through Thursday.
Made-to-order and custom powder coat items show their lead time at the top of this page, right next to the truck icon. These are built fresh for you, so timing varies by brand and current backlog.
Need something by a specific date? Call us at 541-668-7503 before ordering and we will check stock and ETA on that exact part. We can often point you to an in-stock alternative from another distributor.
Questions? Contact us, we respond within 24 hours.
