About the Service

Products covered by the piston exchange service

Engine type
6NY16 6N21 6EY26
6N165 8N21 8EY26
6EY17 M220 6N280
6RY17 6EY22 8N280
6N18 T240 6N330
6EY18 T260 8N330
M200 6N260 6EY33

Introducing the process of manufacturing reconditioned products to ensure quality and safety

1Receiving inspection

The customer sends us a used piston, which we inspect. (Processing may not be possible, depending on its condition.)

Based on the Yanmar standard, professional engineers check if there are cracks, damage, sliding scratches or rust on individual parts.

2Laser Cladding

After inspection, the piston is rough-cut with a lathe and the surface is prepared by sandblasting. After surface preparation, we apply laser cladding to overlay the surface.

As the overlay thickness is easy to control, we can use this process to repair parts that would otherwise be thrown away. It has little thermal impact and produces no strain.

3Final Machining

Final machining is done to the specified size with a lathe.

4Pre-delivery inspection

All products to be delivered are checked by professional engineers according to Yanmar's standards.

We will provide inspection records upon your request.


We may decline to recondition a product or change the fee, depending on its condition.

Service Track Record and Customer Testimonials

More than 1,500 units have been delivered to our customers.

Delivery record of reworked pistons from FY2015 to June 2021
  • After the piston was reworked, the lubricant consumption fell sharply.
  • We don't need to worry about purchasing new pistons, because we can get cheaper ones equivalent to brand new pistons.
  • It only takes as little as a week to recondition a piston.

Reconditioning of Other Parts

1Connecting rod

In apply to prevent excessive deformation of the connecting rod, we propose reconditioning of the connecting rod as a part of preventive maintenance.

【A】Big End

With an engine running for long hours, the big end is distorted in the circularity.

before after

【B】Bolt Seating Surface

The scratched seating surface may cause difficulty to manage the tightening torque. It will cause improper tightening. The scratched seating surface should be corrected by machining. It is necessary to be judged by us if it can be continued to use or not after correcting.

before after

【C】Serration Portion

Many of the cracks occur in the dedendum of serration near the bolt hole on the side of connecting rod body (upper side). YANMAR judges if the part can be used continuously after repairing.

Before Crack detected in the serration portion After Crack of about 2mm can be removed

2Cylinder liner

With long hours' operation of engine, LO consumption tends to increase because LO retentivity decreases due to uneven wear generated on the inner surface of liner and the reduction of honing patterns.
By performing the re-honing, LO retentivity recovers and LO consumption improves.
We offer inspection to detect cracks through Color Check (dye penetrant test), magnetic particle inspection or combination with other test methods.

Before Honing marks Reduction Re-honing process After Re-honing completed

3Idle gear

If the gear bush has worn excessively, the gear backlash will grow, which needs replacement of the bush.
We hone the idle gear bush insert hole securely when replacing the bush, and conduct magnetic particle inspection for the gear tooth surface as well. (YANMAR judges if the part can be used continuously after repairing.)

Gromdomg bush insert hole honing Magnetic particle inspection for the gear tooth surface

4Integrated Fuel Injection Pump

We suggest that periodic overhauling of the fuel injection pump be securely performed. We determine the parts that should be renewed by considering the running hours and the inside conditions when disassembling. We deliver the integrated fuel injection pump after performing the check and adjustment with the dedicated test apparatus subsequent to the completion of the maintenance.

Disassembly of the Pump
Injection Pressure Test
Injection Quantity Test