Products Description
EH12 Generator Piston Assembly +0.50 | Oversize Piston & Ring Kit for Re-Bored Robin-Subaru EH12 4-Stroke Engines
First Oversize (+0.50 mm) Aluminum Alloy Piston with Valve-Relief Crown, Matching Oversize Compression & Slotted Oil Control Rings
EH12 Generator Piston assy +0.5
The correct repair procedure is to remove the engine, take the cylinder block to a machine shop for boring to the first oversize (+0.50 mm), then install this matching +0.50 mm oversize piston and ring kit. The boring process removes the worn, scored, or out-of-round cylinder wall material and produces a perfectly straight, round bore with the correct cross-hatch honing pattern for ring seating. The oversize piston is manufactured from the same high-silicon aluminum alloy as the standard piston, but with its outer diameter precisely matched to the +0.50 mm bore dimension. The piston rings are correspondingly oversized to provide the correct installed ring end gap in the enlarged bore. This kit restores the engine to as-new compression, oil control, and power output with a cylinder bore that is effectively brand new.The kit contents mirror the standard EH12 kit format: piston with dual valve reliefs, a set of oversize rings (compression rings + slotted oil control ring) in a sealed clear bag, a hardened steel wrist pin in protective plastic sleeve, and two wire circlips in a red packet.
Technical Profiles & Materials
When to Use +0.50 vs Standard ：
The oversize selection depends on the cylinder bore condition after measurement by the machine shop. The standard piston is used when the bore wear is within service limits and honing alone restores the surface. +0.50 mm is the most commonly used first major oversize - sufficient material removal to completely eliminate wear ridges, scores, and ovality on a heavily worn cylinder. The machine shop determines the correct oversize based on micrometer measurements of the worn bore.
Complete Oversize Kit ：
The brown box is labeled "EH12+0.50" for unambiguous identification. Each component - piston, ring set, wrist pin, and circlips - is individually sealed to prevent transport damage and ensure all parts are present before the rebuild begins. The ring set is matched to the piston: rings and piston in the same box are the same oversize specification. This eliminates the most dangerous rebuild error - mixing a +0.50 piston with standard rings, or a standard piston with +0.50 rings - where one component is wrong for the bore and the engine either seizes or has no compression.
Technical Specifications
| ITEM | DETAILS |
| Type | Oversize Piston Assembly Kit - +0.50 mm Piston + Rings + Wrist Pin + Circlips |
| Application | Robin-Subaru EH12 (121 cc) 4-stroke OHV engines with cylinder bored to +0.50 mm oversize - generators, water pumps & compact equipment |
| Code | / |
| Material | High-silicon aluminum alloy oversize piston (+0.50 mm), molybdenum/chrome oversize compression rings, slotted steel oversize oil control ring, hardened steel wrist pin, spring steel circlips |
| Details explanation | First oversize: +0.50 mm. Piston crown with dual valve reliefs. Matching oversize ring set (correct end gap in +0.50 mm bore). For professionally bored cylinders only. Complete kit with individually sealed components. |
| Brand Name | SeaSummer |
| Operating Temp | −20 ~ +300 °C (piston crown) |
| Delivery Time | 30 Days |
| Packaging | Cardboard packaging |
Products Application
Engine Machine Shop & Professional Rebuild Services
For engine machine shops specializing in small industrial engine rebuilding, stocking the EH12 +0.50 oversize kit alongside the standard and +0.25 options provides the complete piston solution for any EH12 engine that arrives for rebuild, regardless of bore condition. The "EH12+0.50" box labeling prevents the machine shop from accidentally issuing a standard piston kit for a bored cylinder - a mistake that would result in piston seizure and complete engine destruction on first start. The individually sealed components allow the rebuilder to verify ring-to-piston match before assembly, an important quality-control check in a professional rebuild environment.
Scored Cylinder Repair - Low-Oil & Dust Damage
When an EH12 engine has been run low on oil, the piston skirt scuffs against the cylinder wall, transferring aluminum onto the cast iron bore surface and scoring both components. When a failed air filter has allowed dust ingestion, silica particles embed in the relatively soft piston skirt and act as a lap, wearing grooves into the iron cylinder wall. In both cases, honing alone cannot remove the damage - the scores are deeper than the honing cross-hatch can reach. Boring to +0.50 mm removes the scored material entirely, producing a clean cylinder surface. The matching oversize piston restores the correct piston-to-bore clearance.
EH12 Engine Cylinder Boring & Major Rebuild
This is the sole intended application: installation in an EH12 cylinder block that has been professionally bored and honed to +0.50 mm oversize by a machine shop. The boring process removes the wear ridge at the top of the cylinder (formed where the top piston ring stops at TDC), eliminates bore taper (wider at the top from ring wear, narrower at the bottom), corrects out-of-round (the cylinder wears oval in the thrust direction from piston side-loading), and produces a fresh cross-hatch honing pattern that seats the new rings. After boring, the cylinder is thoroughly cleaned to remove all abrasive grit from the honing process - residual grit in the bore will embed in the new piston skirt and destroy the new rings within minutes of first start.
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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FOR 10000+ OUALITY PARTS
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BACKED BY 200+ TRUSTED FACTORY PARTNERS
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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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