Echo CS590 piston?

[67L36Driver]

I see The Little Red Barn offers two pistons for the 590. A one ring and a two ring.

Is there any reason I can’t use the two ring in a powerhead that originally had a one ring.

I have two powerheads with marginal cylinders and a two ring would fare better in each.

Yikes!! Cylinder kits are expensive. [emoji2960]

 

[Stevetheboatguy]

I believe the 590 and 600 use the single ring and the 620 uses a two ring. @Red97 is that correct or do I have it backwards?


Steven

 

[dgb84]

I believe the 590 and 600 use the single ring and the 620 uses a two ring. @Red97 is that correct or do I have it backwards?


Steven

I just did a muffler mod on 2x 590s in the last week. They both have single ring pistons. I still don’t know why you couldn’t use a 2 ring piston on one, though, as long as the dimensions are the same . Maybe someone smarter than me will chime in. I’m a pretty big dumba$s.

 

[67L36Driver]

I messaged the EBay seller.

We’ll see what he says.

 

[Nutball]

I think it will fit, I'll check my Echo thread to see.

Yes, the 2 ring 620 piston will work in a 590, I'd just be careful about increasing compression with machine work since the top ring is higher than the single ring, putting it closer to where the plating ends at the top of the cylinder, but one could still safely delete the base gasket.

 

[drf256]

620 is definitely a 2 ring and 590 single. Pretty annoying cylinder and piston design. The crown to first ring height on the 620 is right around .100 which is considered to be the minimum reliable amount.

Once I was in the jug, I wanted a 590 piston, the 2nd ring location on the 620 piston is on the side on the ex port.

 

[67L36Driver]

I have two 590’s to fix.

So, I should try one with the two ring piston first to explore for any problems.
[emoji848]

 

[drf256]

Whichever you can find that’s the best quality for the coin. IMHO

 

[David Young]

I think it will fit, I'll check my Echo thread to see.

Yes, the 2 ring 620 piston will work in a 590, I'd just be careful about increasing compression with machine work since the top ring is higher than the single ring, putting it closer to where the plating ends at the top of the cylinder, but one could still safely delete the base gasket.

I think you will free port before you have to worry about the ring of death

 

[67L36Driver]

I think you will free port before you have to worry about the ring of death

We will measure piston crown height very carefully.

 

[Nutball]

I agree, but I think the freeporting will be minimal and not affect performance much, and shouldn't even be an issue unless the cylinder is machined.

 

[drf256]

They are super easy to Freeport, but it don’t do much harm.

This one is probably freeporting 60 thou.

 

[CR888]

That runs like a 70cc saw.

 

[drf256]

That runs like a 70cc saw.

Same size and weight also...

 

[Nutball]

Same size and weight also...

Did you leave out the top ring? .060 of freeporting seems like the upper ring would be off the plating, but then I try to be extra conservative.

 

[67L36Driver]

No measurable difference save for the second ring groove.

The Little Red Barn has ma much thicker skirt by .050”. [emoji15]

Sent from my iPhone using Tapatalk

 

[Nutball]

It must be a Golf piston, they are super heavy.

 

[drf256]

Did you leave out the top ring? .060 of freeporting seems like the upper ring would be off the plating, but then I try to be extra conservative.

No, left out bottom ring.

There is no ROD on the 620 jug IIRC. In fact, I’m pretty sure the squish band, but not the chamber, is plated right up from the bore. I cut in at 0 and only went up around 30 if I recall correctly.

The bottom of the skirt is at the edge of the exhaust floor with the base gasket being deleted. I cut the piston edge and the band flat to match each other.

Super easy to make too much compression in these, but they have a tiny bore for the mass of the jug. There’s a lot of surface area to aid in cooling.

The primary transfers in the 620 are tiny.

 

[67L36Driver]

We got what we wanted. [emoji847]

After we ran it a short time to blow off the assembly oil the compression was 120. Only a marginal improvement over the scored 110. [emoji19]

I ran near a tank of fuel at a very brisk idle and now it is 140. Ta Dah! [emoji106]

Not snagged the bottom ring. [emoji1696]

Treat 590 #2 to a two ring piston next.