Products Description
GX390 +0.25mm Oversize Piston Assembly Kit | Generator Engine Cylinder Rebuild Core
First-Rebore Precision-Matched Reciprocating Module featuring Hypereutectic Alloy Chassis and Pre-Gapped Ring Set for 389cc 4-Stroke Powerhead Cylinder Restoration.
Generator GX390 Piston assy +0.25
The GX390 +0.25mm oversize piston assembly constitutes the definitive cylinder-restoration core engineered for the first-stage rebore and compression recovery of Honda GX390 and compatible 389cc 4-stroke industrial engines. When a cylinder bore has exceeded its serviceable wear limit-exhibiting the taper, out-of-round, and glazed-wall conditions that standard-diameter rings can no longer seal-the cylinder is precision-bored to +0.25mm oversize and this matched piston-and-ring set is installed to restore the exact factory-spec piston-to-cylinder clearance. Fabricated from a high-silicon hypereutectic aluminum alloy with an oval-cam-ground skirt profile, the piston arrives with a complete set of pre-gapped +0.25mm oversize rings, a hardened steel wrist pin, and retaining circlips. Purpose-calibrated as the definitive GX390 cylinder-reconditioning solution, it restores the compression integrity, blow-by containment, and oil-consumption control essential for sustained heavy-load generator and industrial pump operation.
Technical Profiles & Materials
Hypereutectic Al-Si Alloy +0.25mm Chassis Cast from 11%–13% high-silicon hypereutectic aluminum alloy, machined 0.25mm oversize for rebored cylinders. Delivers precise piston-wall clearance to compensate thermal expansion and eliminate piston slap from loose standard-size pistons.
Oval-Cam-Ground Thermal Compensation Profile Asymmetric barrel-shaped piston skirt turns perfectly cylindrical under generator operating heat. It forms stable hydrodynamic oil film, cutting friction loss and excessive oil consumption caused by over-large gaps.
+0.25mm Pre-Gapped Oversize Ring Assembly Matching oversize ring kit with chrome barrel top ring, taper second ring and 3-piece oil control ring. Factory pre-gapped for 88.25mm bore, no manual filing needed to avoid ring butt seizure.
Hardened Wrist Pin & High-Tensile Circlip Retention Case-hardened floating wrist pin fits oversize piston bore accurately. Heavy-duty circlips lock the pin firmly, resisting high-speed reciprocating loads and full compression combustion pressure after engine rebuild.
Technical Specifications
| ITEM | DETAILS |
| Type | First-Rebore Oversize Piston Assembly (+0.25mm) |
| Application | GX390 Generator / Water Pump / 389cc 4-Stroke Engine |
| Code | 1604108 |
| Material | Hypereutectic Al-Si Alloy / Hard Chrome Rings / Hardened Steel Pin / SS Circlips |
| Details explanation | 88.25mm (+0.25mm Oversize, Standard 88.00mm + Rebore) |
| Brand Name | SeaSummer |
| Operating Temp | -20°C to +300°C |
| Delivery Time | 30 Days |
| Packaging | Cardboard packaging |
Products Application
Worn Cylinder First-Stage Reconditioning
Serves as the definitive cylinder-restoration core for machine shops and engine rebuilders performing the first oversize rebore on GX390 cylinders that have reached or exceeded their maximum allowable wear limit. The +0.25mm increment is the standard first-stage oversize, providing a fresh, perfectly cylindrical bore surface while removing the minimum material necessary to eliminate taper, out-of-round, and glazing-preserving maximum cylinder-wall thickness for potential future rebuilds at +0.50mm and +0.75mm stages.
Post-Seizure or Scoring-Damage Recovery
Ideally suited for catastrophic engine restoration following piston-to-cylinder seizure, severe bore scoring from ingested debris or broken ring fragments, or the deep vertical scratches left by a failed wrist-pin circlip that has migrated out of its groove and carved the cylinder wall. The +0.25mm overbore depth is typically sufficient to clean up moderate scoring damage, enabling the engine to be salvaged without jumping to the more aggressive second or third oversize stages that would sacrifice significant cylinder-wall thickness and thermal stability.
Professional Engine-Rebuild Shop Standardization
An essential cylinder-reconditioning spare component for engine-machine shops, generator service centers, and industrial equipment distributors performing professional-grade GX390 overhauls. The complete piston-and-ring kit format eliminates the compatibility risks and assembly errors of sourcing the piston, rings, pin, and circlips from separate suppliers, while the factory pre-gapped rings ensure that the critical end-gap clearance-the most common source of post-rebuild ring-butting .
Quality and Craftsmanship Details
Products Package
About Us
As a premier garden machinery parts supplier, Jiaxing Norsun Trading Co., Ltd. bridges global distributors with over 100 vetted China manufacturers. We streamline your B2B supply chain through strict quality control, flexible production, and factory-direct wholesale pricing. Partner with us for reliable, high-volume sourcing of precision-engineered outdoor power equipment components.
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FAQ
Q: Are you an impartial industrial components dealer or a direct China water pump factors factory?
A:We are a direct, ISO9001-certified engineering water pump components manufacturing facility and precision fluid-control factor manufacture exporter primarily based in China. We function our personal cleanroom injection molding bays, computerized ultrasonic welding arrays, computerized hydraulic stress check stations, and clean-room packaging lines, passing direct-factory wholesale price financial savings straight to your element procurement margins.
Q: Can your manufacturing unit furnish full certification forms for food-contact or consuming water compliance?
A: Yes, absolutely. For food, beverage, or scientific applications, our manufacturing unit makes use of one hundred percent virgin, un-recycled polypropylene resins accompanied by means of fabric traceability certificates. We mechanically furnish B2B purchasers with complete FDA compliance documentation, NSF-grade compound declarations, and RoHS/REACH chemical protection screening sheets to make certain clean clearance thru worldwide customs.
Q: Do you provide customization picks for distinctly corrosive fluids like sturdy acids or ozone?
A: Yes, we are a thoroughly succesful OEM/ODM supplier. For aggressive chemical or ozone environments, we can improve the 12x26.5mm valve configuration in our factory: substituting the general PP housing with top class PVDF (Fluoropolymer) and changing any steel springs with Hastelloy or whole springless gravity-ball architecture, making sure final chemical resistance.
Q: How do we impervious a pattern batch to execute computerized lifecycle and burst-pressure testing?
A: We relatively inspire complete laboratory contrast earlier than logging mass grant agreements. We can ship a pattern lot of 5-10 gadgets of our inventory 12x26.5mm take a look at valves for assessment (setup costs and DHL/FedEx air freight apply). Once the factors pass by your inner lifecycle verification and a formal wholesale quantity manufacturing contract or container run is locked in, the sampling charges are a hundred percent credited returned to your industrial balance.
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