ATHENA Piston Ring Set for YAMAHA DT 125 1991-2004

The ATHENA S410485316001 set of piston rings is designed for YAMAHA DT 125 from 1991 to 2004. Piston rings sit in the grooves of the piston. They seal between the piston and the cylinder, carry heat from the piston into the cylinder and, on a four-stroke, scrape oil off the cylinder walls. Once worn, they let compression leak past: the engine loses its punch.

Specifications

• Brand: ATHENA
• Manufacturer part number: S410485316001
• EAN code: 8051757023615
• For ATHENA piston
• For ATHENA cylinder kit ref. P400485100019 (Ø56 mm)
• Engine: 2-stroke

When to replace it?

• Loss of compression and power, harder starting.
• Ring end gap, measured in the cylinder, larger than the figure in the manual.
• Ring stuck in its groove or showing traces of blow-by.

At every top end inspection, and at the latest when the piston is replaced. On a piston that is still within spec, new rings at mid-life bring the compression back. As a Cross-Mania guideline, the complete piston is replaced every 20 to 40 hours of engine running depending on whether you race or ride for fun.

Fitting tips

1. Clean the piston grooves (a broken old ring makes a good scraper) without widening them.
2. Place each ring in the cylinder, pushed in square with the piston, and measure its end gap with a feeler gauge.
3. Open the rings just enough to slip them over the piston, by hand or with ring pliers: opened too far, they distort or break.
4. Mark facing up, gap correctly located on the pin in its groove: a badly placed ring breaks on the first turn.
5. Lightly oil the cylinder and the rings before reassembly, with a new top end gasket kit.

Why ATHENA?

Athena, an Italian company founded in 1973 near Vicenza, designs gaskets, pistons and cylinder kits for motorcycles. An OEM supplier to KTM, Ducati, Fantic, Piaggio and Triumph and a partner of the MXGP world championship, it develops its parts on the test bench and on the track with racing teams.

Spare parts and items to plan

• ATHENA cylinder kit : ATHENA
• Piston : ATHENA
• Top end gasket kit : ATHENA
• Cylinder head and dome : ATHENA S410485308004 · ATHENA S410485308005
• Exhaust power valve parts : ATHENA
• Spark plug : NGK 3981 · NGK 2411

Frequently asked questions

Which diameter should I choose?
The nominal diameter of your piston, given in the title. The rings go on a piston of the same bore size.

Does the engine need breaking in?
Yes: one hour of gentle break-in, without sustained full throttle, so the rings bed in to the cylinder.

Compatibility

Check the exact model and year of your bike in the list below before ordering.

Fits:
YAMAHA DT 125 2004
YAMAHA DT 125 2003
YAMAHA DT 125 2002
YAMAHA DT 125 2001
YAMAHA DT 125 2000
YAMAHA DT 125 1999
YAMAHA DT 125 1998
YAMAHA DT 125 1997
YAMAHA DT 125 1996
YAMAHA DT 125 1995
YAMAHA DT 125 1994
YAMAHA DT 125 1993
YAMAHA DT 125 1992
YAMAHA DT 125 1991