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pilninggas

2 Stroke ignorance

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Can someone tell me what the 'wiggly' ring is for in a piston kit?

like the one below on the top right:

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Goes on behind the lower piston ring, honestly I don't know what it does, seen it a few times on 2 strokes I have blown u...… er serviced! over the years.

Bit of extra spring maybe, thermal gap, dunno.

The opposite extreme on the daughters scoot, that only has one piston ring.

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10 minutes ago, Cynic said:

Goes on behind the lower piston ring, honestly I don't know what it does, seen it a few times on 2 strokes I have blown u...… er serviced! over the years.

Bit of extra spring maybe, thermal gap, dunno.

The opposite extreme on the daughters scoot, that only has one piston ring.

Ta. I thought it might be an 'expander' for the lower ring.

Funny as there isn't one on either of the existing pistons. I'm gonna leave them out.

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What are they going on, the Suzuki?

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Yes. Just freshening up the top end. Suz's fiches do not show that ring and the original pistons dont have them. Wont bother with them.

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The purpose of the "wiggly ring" is to keep the lower ring central, taking up the free space (regardless of how much space you perceive there to be!)  and keeps the ring central and equi-distant all around.

Just because the original rings don't have them is no basis to leave them out.

You may find that the original ring is a little wider in its cross section thereby not needing them, whereas the newer ring may be that little bit smaller to enable the  'wiggly ring to sit behind it!!  Manufacturers don't include them for fun or as an 'optional extra' after all their R&D.

When I did my engine , i put them in as supplied..... If l had left them out and for whatever reason I wasn't happy with the performance ....I wouldn't want to strip it ALL down again just to put them in!!

Edited by NE0
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I've just been trawling through a few piston ring manufactures websites AE , Hastings, Nevlock, MI, and found an answer to the question of the spring ring behind: ..." It is their to apply additional radial pressure to the piston ring. This increases the unit pressure applied at the cylinder wall. "

 

So there you go.!

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9 hours ago, NE0 said:

The purpose of the "wiggly ring" is to keep the lower ring central, taking up the free space (regardless of how much space you perceive there to be!)  and keeps the ring central and equi-distant all around.

Just because the original rings don't have them is no basis to leave them out.

You may find that the original ring is a little wider in its cross section thereby not needing them, whereas the newer ring may be that little bit smaller to enable the  'wiggly ring to sit behind it!!  Manufacturers don't include them for fun or as an 'optional extra' after all their R&D.

When I did my engine , i put them in as supplied..... If l had left them out and for whatever reason I wasn't happy with the performance ....I wouldn't want to strip it ALL down again just to put them in!!

Good point, well made. I just put one of the expanders behind the lower ring [they are sat on the dining table]. It clearly takes up a small amount of play and keeps the ring more concentric. As it is zero hassle to fit them, i put them in.

Thanks Neo.

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