"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.
Last Edit: Nov 9, 2017 12:15:06 GMT -5 by 90GTVert
Brent Smoking section, please.
Senna1Rossi: Ah, gotcha! Thanks, Fox. Does everyone see the Shoutbox, or just the people who you choose?
Feb 16, 2016 12:39:35 GMT -5
Fox: Anyone who is logged in can see it but it's down at the bottom so most have either chosen to ignore it or haven't discovered it yet.
Feb 16, 2016 18:42:39 GMT -5
Deleted: Wow, I just found this. I feel smart now, ha ha.
Feb 27, 2016 19:24:24 GMT -5
Silar: Ahh.. New feature for a new riding season! YAY!
Mar 16, 2016 17:12:34 GMT -5
Silar: Apparently this still is not being used much. hmm..
Mar 17, 2016 13:55:04 GMT -5
180°off: Anyone want to buy a Yamaha 2t that needs a complete rebuild?
Mar 27, 2016 16:00:19 GMT -5
larryhobman: What is the leanest jet size you would try on a 47mm setup, 60cc stock head with a A9 cam
Apr 2, 2016 20:17:30 GMT -5
Senna1Rossi: Thanks renagade281!
May 23, 2016 14:59:12 GMT -5
Fox: I don't really know how to say this but straight. I am Dave's Girlfriend Kellilee and bluntly and VERY SADLY he passed away early Tuesday morning. I know he would want ya all to know this. Thank You Brent for befriending my love he was very happy on here!
Jun 18, 2016 16:26:04 GMT -5
Fox: www.gofundme.com/29mgf6b8 I hope it is ok to pass on his gofundme page link. If not you will un-post it I'm sure. Thanks again all!!
Jun 18, 2016 16:31:18 GMT -5