Single ring vs. double ring pistons

[cnrcpla]

I have seen the single ring pistons come up a few times but I have never asked how they affect performance. What are some pros and cons to running a single ring? I have always run a wiseco double ring, but I am kind of curious to see if the single ring has any kind of gain to it, or a longer lasting more durable set up. Any opinions out there?

[beaner]

Less friction at the expense of a shorter lifespan.

[cnrcpla]

How about reliability? Would the single have a greater chance of getting snagged on the port?

[beaner]

I do a ring halfway through the season on my 125. If I don't, the power loss is noticeable. I bet if I had a double ring piston, I could run a whole season on a set, and (because I'm not that fast) probably not notice a difference in power over a single ring.

[Jeram]

generally single ring pistons weight alot less than their double ring counterparts.

this means higher RPMS are achievable with less stress on the piston, gudgeon, small end, small end bearing, rod, big end bearing, crank pin, crank, and main bearings.

[2T Institute]

I have seen the single ring pistons come up a few times but I have never asked how they affect performance. What are some pros and cons to running a single ring? I have always run a wiseco double ring, but I am kind of curious to see if the single ring has any kind of gain to it, or a longer lasting more durable set up. Any opinions out there?

Question is why wouldn't you run a single ring, there is NO benefit in a twin ring in a race bike. The single ring pegged on centre running through the C port has no chance of 'snaging' in a port tha is down to the finsh on the port window.
There is no difference in weight of single/dual ring the ring and the extra aluminium in the piston roughly weigh the same.Single ring pistons make more top end HP.

[cnrcpla]

I see. I am really leaning towards try one out next rebuild. It should be interesting, I have never run a single ring before 

[beaner]

Question is why wouldn't you run a single ring, there is NO benefit in a twin ring in a race bike.

You should be able to maintain acceptable compression levels for a longer period of time if you have 2 rings sealing, with not enough loss in power (increase in drag) for somebody at my level. Once that single ring starts to wear, it's over in a hurry. A second ring would help.

[2STROKEREVOLUTION]

I recently went around some other forums to look this up. Here is what I generally found.

Single ring: less friction = more power

Dual ring: Longer lasting, more stable in bore, 2 rings to transfer heat to the cylinder walls so piston stays cooler.

I don't think any of the benefits were that big either way.

[TMKIWI]

For thr average rider there is nothing in it.
I would use what ever the manufactor recomends.
I use a wossner single ring because that is all that fits the tm.
I have read up on fitting the Gas Gas 2 ring piston into the tm but from what I can find the benifits are not any better because of the port arrangement.
So just use what is recomended unless you are about to take on RV or someone similar.

[2T Institute]

Question is why wouldn't you run a single ring, there is NO benefit in a twin ring in a race bike.

You should be able to maintain acceptable compression levels for a longer period of time if you have 2 rings sealing, with not enough loss in power (increase in drag) for somebody at my level. Once that single ring starts to wear, it's over in a hurry. A second ring would help.

Just how much and for how long would it keep compression up? The rings  wear at a simlar rate or is the second one there to just pick up the slack somehow? When a ring costs $20 odd and takes an hour or so to replace I don't understand the logic. That keeping a component way past it's life is somehow more cost effective?

Dual ring: Longer lasting, more stable in bore, 2 rings to transfer heat to the cylinder walls so piston stays cooler.

Rings don't help piston rock, and the same person that says that twin rings make the piston run cooler(they do but it's very marginal due to increase in friction as rpm rises) will run 50:1 oil.

A thing to notice is it governed by bore size and rpm. Bigger bore engines will tend to have 2 rings smaller bore single rings.

[Stusmoke]

I run a Wossner single ring in my 2001 Honda CR125 and its a terrific piston you can tell just by looking at it some engineers over in Germany have put some serious thought into its design.

I would recommend it to anyone. I push this little zinger to its limits by the way, it takes the punishment well. Run the Wossner next time your 250 is due for a topend, see how you go. Its probably one of the best pistons money can buy so its quality made. Try it, see how you go.

[beaner]

Just how much and for how long would it keep compression up? The rings  wear at a simlar rate or is the second one there to just pick up the slack somehow? When a ring costs $20 odd and takes an hour or so to replace I don't understand the logic. That keeping a component way past it's life is somehow more cost effective?

The purpose of the rings is to seal. If there are 2, then it will seal better, for longer than 1. Even if both rings are worn similar to the single, 2 rings will still seal better. If it is sealing, the amount of wear is not important, and you are not using it past it's life.

[2STROKEREVOLUTION]

Dual ring: Longer lasting, more stable in bore, 2 rings to transfer heat to the cylinder walls so piston stays cooler.

Rings don't help piston rock, and the same person that says that twin rings make the piston run cooler(they do but it's very marginal due to increase in friction as rpm rises) will run 50:1 oil.

The rock and heat transfer from 2-rings was what I read on MacDizzy.

What is your point on the 50:1?

A thing to notice is it governed by bore size and rpm. Bigger bore engines will tend to have 2 rings smaller bore single rings.

Wossner's 380 piston is a single ring, and that is a 78mm bore. Stock and Wiseco are twin ring.

[cnrcpla]

Define unstable, like it has a higher chance of just grenading or something? Or freezing in the ring groove? I have done a bit of research, but nothing defines what "unstable" means in the case of piston rings.