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One ring vs two

Moparmyway

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Without mentioning any names of who built something .............

1. Is there an advantage of removing the bottom or top ring ?
2. What gains would I expect to see if I removed one of the two rings ?
3. Is there any truth to the "rumor" that removing the lower ring results in a dry bottom end ?
4. What losses should I expect to have with the lower ring removed ?
 

Moparmyway

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i would start by saying that it would probably depend a bit on ring thickness.
Would that be a determining factor in which ring you removed (the top or the bottom ring) ?
 

Moparmyway

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When I do a 51.4mm XPW top end, I leave out the lower ring.

It's too close to the transfer port to allow any widening at all. Those ports need to be widened just to be as large as the 50mm jug.
Not pointing to any specific saw, but on a two transfer port, two ring piston, have you seen any gains by removing one of the two rings ?
 

Moparmyway

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I would remove only the bottom ring, not sure why, just seems right. Lol
In doing so, wouldnt the piston be less stable in the bore than compared to removing the upper ring instead ?
 

Deets066

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I bet it's more stable with the top ring than it would be with the bottom ring. The rod bearing is the pivot point, the upper ring is farther from the pivot point which I believe would give it better stability
 

Mastermind

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Not pointing to any specific saw, but on a two transfer port, two ring piston, have you seen any gains by removing one of the two rings ?

I've done that on a cant saw.....to free it up. You'll find more RPM.

I've owned several 371's and 372's and I haven't done a timed comparison but they run pretty close.
Why did Husky go to a 2 ring on the 372 ?

Heat dissipation.
 

Deets066

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Why would that be the case as opposed to removing the lower ring ?
It would make the area from the "seal/ring" a larger volume. As opposed to the top ring sealing closer to the combustion chamber giving it less volume. Probly such a small amount that you wouldn't notice on a gauge though
 

Mark71gtx

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I think in 4 stroke because I have always dealt with cars, so bear with me. It seems to me that the lower ring, being lower, would make the combustion chamber seem larger, not by much, but some amount. When trying to gain compression in a V8, we would use thin head gaskets, and/or shave the heads to make the chamber smaller.
 

Moparmyway

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I think in 4 stroke because I have always dealt with cars, so bear with me. It seems to me that the lower ring, being lower, would make the combustion chamber seem larger, not by much, but some amount. When trying to gain compression in a V8, we would use thin head gaskets, and/or shave the heads to make the chamber smaller.
We do that in 2 strokes as well, by cutting the top of the chamber and the base, we "tune" the squish and raise compression, along with altering timing numbers, of course
 
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