Echo 590 vs 620P

[Nutball]

I got an old wrist injury giving me problems again, so that's why there's a delay. I'll get it checked out soon. It's not bothered much by porting, just working on saws and similar tasks. These saws have some really tight screws!

Anyway, the 590: .040 squish, EX: 111, TR: 127, IN: 76.

I did notice the 620 was able to rev up much higher. I made some cuts tuned to 13,800 (stock) and then tuned to 13,400. It and the 372 had a quiet full throttle 4 stroke sound making them a little hard to tune at first until I realized how subtle of a sound I was listening for. Maybe it's the restricted mufflers which I'm not used to.

 

[Nutball]

The carbs are different, the 590 has a ventury of about 15.05mm, the 620: about 15.87mm.

 

[TreeLife]

Real world weights of the echos?

Are you an echo dealer? @Nutball

 

[Nutball]

Nope, I just like them: affordable, torquey, high oil output.

620P: .035 squish, EX 105-6, TR 125, IN 78-9. Looks about right according to how it handled. Interesting how they seemed to perfectly compensate the squish with the exhaust height to get the same compression unless my gauge just likes 136psi.

Now that they are in pieces I can weigh them. They were too heavy for my precision scale.

 

[huskihl]

Nope, I just like them: affordable, torquey, high oil output.

620P: .035 squish, EX 105-6, TR 125, IN 78-9. Looks about right according to how it handled. Interesting how they seemed to perfectly compensate the squish with the exhaust height to get the same compression unless my gauge just likes 136psi.

Now that they are in pieces I can weigh them. They were too heavy for my precision scale.

So you're thinking they set the height of the exhaust to get the desired compression?

 

[Nutball]

So you're thinking they set the height of the exhaust to get the desired compression?

No, I think they lowered the squish to .035 instead of .040 because of the high exhaust, to maintain compression. I've found other 590's to be .040 also.

 

[USMC615]

Interesting thread.

 

[Nutball]

The 620 has 2 rings with the upper ring pin centered on the intake side like the 590, and the lower pin is on the flywheel side of the exhaust port. The 590 has only one ring. The 620 cylinder is labeled "1" on the base, 590 is "2". The exhaust and transfer ports are definitely higher on the 620, the intake port doesn't appear any lower at least relative to the squish band. The transfers are the same shape on both saws with similar chamfer patterns, but simply taller openings with a steep sloped rear, and a very flat exhaust side transfer.




The 620 muffler has larger holes in the baffle to flow through to the second half more easily. It also has spacers welded to the lower mounting holes, and the 620 case has been machined to accept them. If you want to use a 590 muffler on a 620, you will need spacers to fill the gap behind the lower mounts.

 

[Nutball]

14.00lbs for the 620. This is a newer version of the saw, but I've measured a ported 303t to be I think .1lbs heavier than advertised, but a non cat stock 2511t to be less than advertised.

13.70lbs with optional clutch cover spikes (almost a must have in my opinion).

 

[huskyboy]

So it weighs more than a 372 OE and slower than one too. Hmm. Time to mod them and change that lol. Appear to be well made saws regardless though and priced well too.

 

[Nutball]

A 590 with empty tanks and a 24"b/c was about 1.4lbs less than a Y2K 372xp with 18" b/c and some gas and oil. And the 620 with some gas and oil and a 20"b/c is about 1.6lbs lighter than the 372 with the same B/C.

I figure I'll port the 590 for torque, and the 620 for peak power. Might as well. And I'll go for lots of compression on both via a popup and cutting a lot off the cylinder bases.

 

[Nutball]

Looks like the crown to ring distance is basically the same as the no plating zone at the top of the cylinder on both saws, so it is safe to drop the cylinder a squish band's distance. The paper base gasket appears to be .010" when measured as I have also noticed in the past by the amount the SB decreased.

 

[TreeLife]

Cant wait to see how this works out, I've been looking at echos for a long time.

 

[Red97]

Don't drop too far they like to free port easy...

 

[Red97]

I really like this thread. Keep up the good work.

 

[David Young]

Looks like the crown to ring distance is basically the same as the no plating zone at the top of the cylinder on both saws, so it is safe to drop the cylinder a squish band's distance. The paper base gasket appears to be .010" when measured as I have also noticed in the past by the amount the SB decreased.

you should put the pistons at tdc and mark the exhaust port on the piston with a pencil to see how much is available to drop the cylinder. I am having a discussion with a friend. I see a large amount of room on a 590 piston. But Stihlbro opened a 620 and showed there wasn’t a lot of room to drop the jug.
Are the pistons the same overall length?

do the jugs have the same combustion chambers?

 

[Nutball]

Same chambers, slightly different plating gap between where the plating ends and squish band. With the pistons all the way in there is no visible free porting, any further and you might see some, but the end of the plating will prevent you from dropping the cylinder that far at the risk of the ring running off the plating. You might get away without the top ring on the 620 for more compression, but you should plug the ring slot with something to avoid loosing mix from the transfers out the exhaust. I don't know if JB would last with all the thermal expansion cycles. I have an aluminum wheel sitting outside with what looks like JB weld on it to plug a crack. After a few years of sitting outside, the JB is peeling clean off the wheel. Maybe the surface wasn't prepped well, maybe weather degraded the epoxy, but I'm wondering how long JB can last in an engine before letting loose.

The 590 piston is about 1g heavier, and they appear to be the same height/length, so it looks like the same piston is used, but with a higher and much lower ring slot in the 620.

They use ear-less piston pin clips, and depending on the way they were put in, may or may not be so easy to get out. One was not coming out without getting bent out of shape, so I ordered a bunch more. First one I've had trouble with.

 

[Nutball]

Busy week, Hopefully I'll have time to test run them Saturday.

 

[Cut4fun]

So it weighs more than a 372 OE and slower than one too. Hmm. Time to mod them and change that lol. Appear to be well made saws regardless though and priced well too.

Really like the thread. Thanks OP

Also just to add these to it. Dealer in my group was selling the 590 for 299 and the 620 for 449.

590 and OE 372

But yes 372 feel.

 

[Nutball]

Really like the thread. Thanks OP

Also just to add these to it. Dealer in my group was selling the 590 for 299 and the 620 for 449.

590 and OE 372

But yes 372 feel.

View attachment 205920 View attachment 205921

Wow, let me know when they do that again. That sounds a little lower than they normally go. I think the usual discount for dealer days is 15%.


I wonder why they went with 2 rings on the 620? I had a plan for the final major step in turning a 590 into a peaky saw, but put that recipe into the 620 instead. I partially used an extra high popup to achieve the port timings in case I want to go backwards a little with a new piston if need be. The squish still ended up around .035, I think there will still be a slight gain in compression. I'd guess maybe 145psi hot considering it did 180psi cold and oily. I can't help but think about removing the top ring and really getting some compression. There is the slightest bit of free porting going on already, you almost can't see through it.



98, 125, 90 I think the transfers could go a little higher, and intake slightly lower, but it has a bigger carb which will decrease the need for intake duration.