Yamaha Piston rings – Regular vs Keystone – Explained

Piston Ring Design: Standard vs. Dykes-Style in Yamaha Two-Strokes

When it comes to Yamaha’s legendary two-stroke engines, every detail of their design played a role in performance, reliability, and longevity. One often-overlooked but critical component is the piston ring. While most riders are familiar with standard piston rings, Yamaha also used a unique alternative—the Dykes-style piston ring—on some of their high-performance models. But what exactly is the difference between these two designs, and why did Yamaha choose to use them?

To answer these questions, we’re taking a look at an official Yamaha service bulletin from 1969, which provides insight straight from the factory. Below, you’ll find scanned copies of this technical documentation, along with an explanation of how each piston ring type affects engine performance.   

So go ahead and memorize all this information and you can then impress or bore all your buddies. 🙂