Post by 90GTVert on Jan 31, 2011 22:27:55 GMT -5
"My big bore kit came with an extra ring that's really thin. What's it for?" That's a relatively common question in two-stroke sections, so here's the answer.
Here's a 2T piston kit. You can see the piston, two standard compression rings, and then "that thing".
Here's a better picture of the little guy.
So, what is it? It's an expander or expansion ring. This thin piston ring is designed to sit behind the lower ring to expand it outward into the cylinder walls, as shown below.
Now we know what it is, and where it goes, but should you use it? Maybe. I say no. Other's say yes. I feel that it is not necessary on any kit in good working order, as a brand new cylinder kit should be. Even on older, worn, kits it doesn't seem like a great idea to me. I've read about these fragile little rings breaking. If they break, you now have small pieces of metal banging around inside the engine. Not good. The only way I'd consider installing one of these would be if the piston ring end gap was above spec. Even then, I'd prefer a new set of rings.
For those that think the engine won't run properly without them, have a look around and you will discover that high end, high RPM, big bore kits are commonly made with only a single ring. No, I'm not suggesting to use only one ring with your dual ring kit.
Here's a 2T piston kit. You can see the piston, two standard compression rings, and then "that thing".
Here's a better picture of the little guy.
So, what is it? It's an expander or expansion ring. This thin piston ring is designed to sit behind the lower ring to expand it outward into the cylinder walls, as shown below.
Now we know what it is, and where it goes, but should you use it? Maybe. I say no. Other's say yes. I feel that it is not necessary on any kit in good working order, as a brand new cylinder kit should be. Even on older, worn, kits it doesn't seem like a great idea to me. I've read about these fragile little rings breaking. If they break, you now have small pieces of metal banging around inside the engine. Not good. The only way I'd consider installing one of these would be if the piston ring end gap was above spec. Even then, I'd prefer a new set of rings.
For those that think the engine won't run properly without them, have a look around and you will discover that high end, high RPM, big bore kits are commonly made with only a single ring. No, I'm not suggesting to use only one ring with your dual ring kit.