Echo 490 to ported 4910…to cs-5484

[Ketchup]

I got this 490 for free. Some folks were saying that a 490 piston might do good things in a 4910 jug, so why not?

I read around to get an idea of where I wanted to go with this saw. I might as well save the next guy some search time:

Echo 4910/501p “shortcomings”

As some know, I’m quite a fan of these little guys in ported form. Tons of features I love about them. Some called these a 346 killer, I don’t know about all that but I think it’s a possibility. These saws are consistently hitting 5.5hp on @Red97 ’s dyno, that’s pretty impressive for a $300...

opeforum.com

Echo cs 490 porting

Well to keep the clutter out of the 590 thread, I will start this one. First cuts brand new out of the box, limiters, 18" .325 oregon semi chisel. Decent compression sotck. Plenty of skirt on this one, .043 off the base. Better. Piston wash. Pretty much identical to the 500p in...

opeforum.com

Another chainsaw dyno...

I'll drop this here. If anyone is interested in dyno service, or any other service. We just launched the site. www.worksaws.com Let me know what you think. I know it needs some tuning yet. Good deal Joe. I'm passing your site to my non OPE saw friends.

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Echo 501P. Let's play!

Ok boys. This maybe a super slow build thread. As I really like what im seeing so I may hold off doing any drastic changes till I can sell a couple saws and buy another one. That said. Let's get started. @WSE15 could you post up a few of the exterior pics?

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I’ve never been in one of these before.
First impression is that the jugs really aren’t that different, but the intake on the 490 is way too low. Transfer uppers are a little undersized in the 490. The 4910 transfer uppers are unusual. 490 has a D chamber.

 

[Ketchup]

The 490 piston does seem better. Plenty of skirt. I don’t understand the windows in the 4910 piston. The transfers are bottom fed in both saws. Wouldn’t the windowed piston just create turbulence along the cylinder wall? Maybe I’m over simplifying, but what’s the point of windows if the transfers aren’t side fed?

Anyway, here’s the wash pattern from the 490 Jug. Looks like the secondaries aren’t doing enough.


Stock 4910 ports on the 490 piston:
You can see how much lower the intake was on the 490.


My starting line:


I’m thinking 76/110/128p131s with the exhaust widened to 65%. Cut the base 0.040”, leave the band stock and keep the gasket.

@Red97 , @farminkarman, @Scarr, @Dolkitafreak, you guys seem to have worked on this platform a lot. Do you think a carb alternative is necessary? 590 carb? Is the 490 coil a problem?

More to come…

 

[farminkarman]

The 490 piston does seem better. Plenty of skirt. I don’t understand the windows in the 4910 piston. The transfers are bottom fed in both saws. Wouldn’t the windowed piston just create turbulence along the cylinder wall? Maybe I’m over simplifying, but what’s the point of windows if the transfers aren’t side fed?

Anyway, here’s the wash pattern from the 490 Jug. Looks like the secondaries aren’t doing enough.
View attachment 364321

Stock 4910 ports on the 490 piston:
You can see how much lower the intake was on the 490.
View attachment 364320View attachment 364322

My starting line:
View attachment 364319

I’m thinking 76/110/128p131s with the exhaust widened to 65%. Cut the base 0.040”, leave the band stock and keep the gasket.

@Red97 , @farminkarman, @Scarr, @Dolkitafreak, you guys seem to have worked on this platform a lot. Do you think a carb alternative is necessary? 590 carb? Is the 490 coil a problem?

More to come…

I don’t deserve any credit on developing these. That being said, I think the stock carb is fine if you are shooting for a worksaw. If you wanted to run a higher exhaust and hit higher rpm, I think the stock carb is going to hold it back. The 4910 I built had a 108 exhaust roof and it made like 5.2hp. If I were to do one again, I would like to try either a 490 piston or a Husky 44mm 350 piston to allow a wider exhaust and shorter blowdown.

 

[Ketchup]

I don’t deserve any credit on developing these. That being said, I think the stock carb is fine if you are shooting for a worksaw. If you wanted to run a higher exhaust and hit higher rpm, I think the stock carb is going to hold it back. The 4910 I built had a 108 exhaust roof and it made like 5.2hp. If I were to do one again, I would like to try either a 490 piston or a Husky 44mm 350 piston to allow a wider exhaust and shorter blowdown.

Isn’t the 350 piston a different wrist pin size?

 

[Ketchup]

40 thousands off both. Enough for tonight.

 

[Red97]

The 490 piston does seem better. Plenty of skirt. I don’t understand the windows in the 4910 piston. The transfers are bottom fed in both saws. Wouldn’t the windowed piston just create turbulence along the cylinder wall? Maybe I’m over simplifying, but what’s the point of windows if the transfers aren’t side fed?

Anyway, here’s the wash pattern from the 490 Jug. Looks like the secondaries aren’t doing enough.
View attachment 364321

Stock 4910 ports on the 490 piston:
You can see how much lower the intake was on the 490.
View attachment 364320View attachment 364322

My starting line:
View attachment 364319

I’m thinking 76/110/128p131s with the exhaust widened to 65%. Cut the base 0.040”, leave the band stock and keep the gasket.

@Red97 , @farminkarman, @Scarr, @Dolkitafreak, you guys seem to have worked on this platform a lot. Do you think a carb alternative is necessary? 590 carb? Is the 490 coil a problem?

More to come…

I take the up 106 ish and
126-128 just enough to match the transfers, maybe raise a degree or so.

 

[drf256]

When Joe and I did them back to back (there’s some old thread) I compared the 346 transfer tunnels to the 490. The Echo transfers lack that “swoop” that the 346 have at the roof.

Echo cs 490 porting

Well to keep the clutter out of the 590 thread, I will start this one. First cuts brand new out of the box, limiters, 18" .325 oregon semi chisel. Decent compression sotck. Plenty of skirt on this one, .043 off the base. Better. Piston wash. Pretty much identical to the 500p in...

opeforum.com

The 4910 transfers look much better overall, but the sharp entry angle has to hurt the, a bit.

 

[drf256]

I tried to open the Venturi of the stock carb on mine and found a hidden fuel passage quite quickly as well.

 

[Ketchup]

When Joe and I did them back to back (there’s some old thread) I compared the 346 transfer tunnels to the 490. The Echo transfers lack that “swoop” that the 346 have at the roof.

Echo cs 490 porting

Well to keep the clutter out of the 590 thread, I will start this one. First cuts brand new out of the box, limiters, 18" .325 oregon semi chisel. Decent compression sotck. Plenty of skirt on this one, .043 off the base. Better. Piston wash. Pretty much identical to the 500p in...

opeforum.com

The 4910 transfers look much better overall, but the sharp entry angle has to hurt the, a bit.View attachment 364402View attachment 364403View attachment 364404View attachment 364405View attachment 364406

Glad you’re here Doc. Sorry I missed you in my second post.

Pulling the 490 apart and looking at the wash pattern, it looks like scavenging is missing the intake side of the piston crown. Did you try to flatten out the angle on your uppers? The 4910 primary looks okay, but the secondary is aimed at the chamber. Would you flatten that?

Also, why is this in there?

 

[huskihl]

Glad you’re here Doc. Sorry I missed you in my second post.

Pulling the 490 apart and looking at the wash pattern, it looks like scavenging is missing the intake side of the piston crown. Did you try to flatten out the angle on your uppers? The 4910 primary looks okay, but the secondary is aimed at the chamber. Would you flatten that?

Also, why is this in there?
View attachment 364420

Don’t know what the mark in your red circle is. Probably a slight casting defect.

The secondaries aren’t going to wash the piston crown being pointed up on a 45° angle. But the mains should wash it a little if they open first by a few degrees

 

[Ketchup]

Don’t know what the mark in your red circle is. Probably a slight casting defect.

The secondaries aren’t going to wash the piston crown being pointed up on a 45° angle. But the mains should wash it a little if they open first by a few degrees

It definitely looks like a mistake, but it’s identical on both sides. It’s also a very nicely shaped port. Everything funnels to the leading corner, even the chamfer.

Seems like the Echo engineers have a bit extra experimental liscense. There are quite a few goofy design details in the current echo models. Kind of reminds of the ripples in a 592 upper. I’m going to get rid of it and lower the angle to 10ish degrees.

Edit: Something I hadn’t thought of until just now: that port may have been carved by some sort of machine like a cnc. Maybe the cutter head couldn’t reach that corner perfectly.

 

[Ketchup]

Didn’t get very far today. Got the epoxy set in the 490 jug. Then the truck broke down. At least it was in the driveway.

I epoxy the intake just like Tree Monkey’s video. A rough burr with no lubricant to make a fresh, coarse surface. Then just high pressure air to get it clean. I used to use brake cleaner, which apparently is a big mistake. Then I mix JB weld careful not to work in air bubbles. I have a tiny metal spatula tool to push the epoxy into the corners of the port. I work from the center to corners and use plenty of epoxy.

 

[huskihl]

It definitely looks like a mistake, but it’s identical on both sides. It’s also a very nicely shaped port. Everything funnels to the leading corner, even the chamfer.

Seems like the Echo engineers have a bit extra experimental liscense. There are quite a few goofy design details in the current echo models. Kind of reminds of the ripples in a 592 upper. I’m going to get rid of it and lower the angle to 10ish degrees.

Edit: Something I hadn’t thought of until just now: that port may have been carved by some sort of machine like a cnc. Maybe the cutter head couldn’t reach that corner perfectly.

Echo seems to have a little bit different outlook on things, trying to get old-school motors to pass emissions. I believe their designs are quite efficient, just can’t push much power in through smaller carbs and get a bunch of power out through a narrow exhaust and still meet emissions

 

[huskihl]

Didn’t get very far today. Got the epoxy set in the 490 jug. Then the truck broke down. At least it was in the driveway.

I epoxy the intake just like Tree Monkey’s video. A rough burr with no lubricant to make a fresh, coarse surface. Then just high pressure air to get it clean. I used to use brake cleaner, which apparently is a big mistake. Then I mix JB weld careful not to work in air bubbles. I have a tiny metal spatula tool to push the epoxy into the corners of the port. I work from the center to corners and use plenty of epoxy.

View attachment 364508View attachment 364509

If you heat the port a little bit, it will flow and level like syrup, rather than honey. Works well for getting rid of air bubbles too

 

[drf256]

I wouldn’t flatten the secondaries at all.

The primary sweeps the piston and the secondary pushes the charge up toward the intake side chamber. The bigger secondary gets less pressure.

The primary is nice and tight and should prevent charge short circuiting out if the exhaust port.

Must be an echo thing, the 590/620 are similar in design. Small primary with big secondary and steep angle. The secondary is hard to raise on the 620 because of it.

My biggest issue with those jugs in the sharp turn that the charge has to make from the tunnel to the transfer roofs. Other designs expand there and allow the air to make a nice curve. The Echo truly makes a sharp 90* turn there. Air doesn’t like to flow that way.

 

[Ketchup]

I wouldn’t flatten the secondaries at all.

The primary sweeps the piston and the secondary pushes the charge up toward the intake side chamber. The bigger secondary gets less pressure.

The primary is nice and tight and should prevent charge short circuiting out if the exhaust port.

Must be an echo thing, the 590/620 are similar in design. Small primary with big secondary and steep angle. The secondary is hard to raise on the 620 because of it.

My biggest issue with those jugs in the sharp turn that the charge has to make from the tunnel to the transfer roofs. Other designs expand there and allow the air to make a nice curve. The Echo truly makes a sharp 90* turn there. Air doesn’t like to flow that way.

Good point about the big transfer being low pressure. Are you saying the transition is a flat angle in the uppers instead of a sweep? Like in a 200t?

Edit: Okay, I think I understand now. I made a drawing. I’ll try to grind a better transition in the back but I agree it’s not as good.
Looking closer into the transfer uppers, the rear exit angle is gronked. Hopefully I can clean that out too. Sorry for the bad photo.





Any thoughts on swapping in a 590 carb? @Red97 , seems like you may have looked into that. I don’t want to buy one just to find out it’s the same or won’t line up. Looks possible from photos.

If you heat the port a little bit, it will flow and level like syrup, rather than honey. Works well for getting rid of air bubbles too

That’s excellent info. I’ll try it. Thanks!

 

[Ketchup]

Since I had a 346 jug down to look at…


The case would need clearance work to drop the the 346 jug onto the 490 case but it looks doable.

The bolt pattern is the real problem. The upper right corner in the photo would be stretched beyond the edge of the base.

Another problem is the wrist pin bearing. 346 is 10mmIDx14mmOD. 490 is 11mmx15mm. Not sure how hard it would be to find a 10mmx15mm in the same length.

Better get grinding.

 

[Dolkitafreak]

I have tried a low exhaust (105-108) and it always felt lazy to me. I have tried many different upper changes, now I base cut it .040”, set exhaust to 102, primaries 122, leave secondaries alone which is a huge stagger but they fill the chamber well, and drop intake to 80. Good attitude work saw that will pull a 20” 3/8 bar fine in hardwood.

 

[huskihl]

I have tried a low exhaust (105-108) and it always felt lazy to me. I have tried many different upper changes, now I base cut it .040”, set exhaust to 102, primaries 122, leave secondaries alone which is a huge stagger but they fill the chamber well, and drop intake to 80. Good attitude work saw that will pull a 20” 3/8 bar fine in hardwood.

Can you come straight out at 102 without blowing through the roof?

 

[Dolkitafreak]

Can you come straight out at 102 without blowing through the roof?

Pretty close to it. I roll into the port slightly and haven’t blown through one yet.