Echo cs 490 porting

[echoshawn]

I think I have a good 1-2 punch here now.
600 runs good, will be better once it has a mastermind sticker on it

 

[drf256]

Damn. The exhaust port is annoying.

That right angle it comes off the jug at. Sheesh....

I got some ideas....

 

[Red97]

Damn. The exhaust port is annoying.

That right angle it comes off the jug at. Sheesh....

I got some ideas....

Make it happy

 

[BGE541]

I think I have a good 1-2 punch here now.
600 runs good, will be better once it has a mastermind sticker on it

Mike @rattler makes a mean Echo

 

[CoreyB]

Can't wait to see the video's

 

[drf256]

I'm at an exhaust of 129 and an intake of 74-91.

I Devcon'd the intake last night.

I'm a bit worried that there is not enough physical meat where the exhaust port meets the jug to cut up 20+*.

Red, how many degrees was that lip of plating on the exhaust roof? This is an odd design, the exhaust port has a lip of plating sticking out around its perimeter. So the port itself is larger than the port opening from the cylinder.

This is opposite of what I've seen in most Stihl's. Usually on Stihl's, the chamfers are huge and the port is much smaller than the opening in the plate.

I'm hoping I can manage 108 from the exhaust. The top of the transfers can be epoxied, but the hottest part of the hottest port on the saw has to be bustin my balls now.

 

[Red97]

I'm at an exhaust of 129 and an intake of 74-91.

I Devcon'd the intake last night.

I'm a bit worried that there is not enough physical meat where the exhaust port meets the jug to cut up 20+*.

Red, how many degrees was that lip of plating on the exhaust roof? This is an odd design, the exhaust port has a lip of plating sticking out around its perimeter. So the port itself is larger than the port opening from the cylinder.

This is opposite of what I've seen in most Stihl's. Usually on Stihl's, the chamfers are huge and the port is much smaller than the opening in the plate.

I'm hoping I can manage 108 from the exhaust. The top of the transfers can be epoxied, but the hottest part of the hottest port on the saw has to be bustin my balls now.

I never checked the thickest of that lip, but it can't be much more than 2*

When I did the ex I centered by burr in the port went to my line, which was about 2* high set it at 110 with a ring first. Ended up at 108. It was a lil nerve racking taking it to 106, but I didn't see any light on the other side.
I will admit the roof is not perfectly flat front the port to the outlet. But I wasn't going to chance breaking through.

You should be able to make it to 108, but remember the dome on the piston, throws the # off about 2* when marking with a ring.

Since I had the skirt length, I changed the exhaust angle from the factory 90* to an 86* ish that helped with not breaking through the roof. Altho not ideal, I couldn't come up with many options.

 

[David Young]

I'm at 129 Exhaust and 74-91 intake.

View attachment 16066


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anyone else wonder what a saw would run like with the exhaust that low?

Probably turn 5000 rpm but pull a 404 chain.

 

[jmssaws]

anyone else wonder what a saw would run like with the exhaust that low?

Probably turn 5000 rpm but pull a 404 chain.

I tried a 394 at 110 for the hell of it,it didn't work very well.

 

[Red97]

anyone else wonder what a saw would run like with the exhaust that low?

Probably turn 5000 rpm but pull a 404 chain.

Probably true, but I have a Sez for that...

For this I want a viable 346 replacement. Searching for carb options...

 

[Miller Mod Saws]

Probably true, but I have a Sez for that...

For this I want a viable 346 replacement. Searching for carb options...

Subbed. Nate looked for me and didn't find a direct fit one off the echo lineup. So I opened up the venturi a little.

 

[Red97]

Subbed. Nate looked for me and didn't find a direct fit one off the echo lineup. So I opened up the venturi a little.

Factory is 13.5 venturi
Found a 14.25 venturi in the same "wt" series. Should be fairly easy to adapt. Might have to swap shafts/linkages but should be doable, being from the same carb family.

Might try and find another body to bore out. Should be able to get it to 14.5 easy enough.

What rpm did your saw stop? 13k? Would it lean out farther than that? Or just would not spin higher?

Drf255, what carb are you running on your 026's? They are a walbro "wt" series correct? Seems those spin pretty high.?

This with stock limiters was lean at 12,200. Sounded much better at 11,500.

 

[echoshawn]

I gotta get a new video camera and tripod so I can shoot some video.
The 500 definitely woke up with the little work I did.
Still doesn't rev up as fast as I thought it would. Needs more fine tuning.
Running 20" 3/8 full comp it pulls down but doesn't quit.

 

[drf256]

Factory is 13.5 venturi
Found a 14.25 venturi in the same "wt" series. Should be fairly easy to adapt. Might have to swap shafts/linkages but should be doable, being from the same carb family.

Might try and find another body to bore out. Should be able to get it to 14.5 easy enough.

What rpm did your saw stop? 13k? Would it lean out farther than that? Or just would not spin higher?

Drf255, what carb are you running on your 026's? They are a walbro "wt" series correct? Seems those spin pretty high.?

This with stock limiters was lean at 12,200. Sounded much better at 11,500.

I'm running a WT194. Yeah, 14,500 easy with a 105 exhaust and the WT194. An 044 Carb will give another 1K rpm.

EDIT: 13.45mm venture on the 194

 

[Miller Mod Saws]

Factory is 13.5 venturi
Found a 14.25 venturi in the same "wt" series. Should be fairly easy to adapt. Might have to swap shafts/linkages but should be doable, being from the same carb family.

Might try and find another body to bore out. Should be able to get it to 14.5 easy enough.

What rpm did your saw stop? 13k? Would it lean out farther than that? Or just would not spin higher?

Drf255, what carb are you running on your 026's? They are a walbro "wt" series correct? Seems those spin pretty high.?

This with stock limiters was lean at 12,200. Sounded much better at 11,500.

IIRC it was 13400 or there about. And it just give it up. No matter how much you leaned it out.

 

[Red97]

I'm running a WT194. Yeah, 14,500 easy with a 105 exhaust and the WT194. An 044 Carb will give another 1K rpm.

EDIT: 13.45mm venture on the 194

Ok, so similer bore stroke and 1000 rpm less in these echo. Even with roughly the same venturi size. Is that extra 3-5* on the exhaust the 1k loss in rpm vs the stihl?

IIRC it was 13400 or there about. And it just give it up. No matter how much you leaned it out.

Thank you, that was the exopxyed intake saw and bored carb?

Hopefully I can get the 14.25 carb to work. To test this theroy.

I know my 346 likes the 16.66 venturi carb.

 

[bikemike]

Maybe we are all looking at what is already done and need to look at a different possibility. The MUFFLER MOD. Maybe having a outlet tube in the exhaust with a bigger ID will change results in that. Or a baffle may be causing a restriction to let gasses escape from the port. I don't know what that canister look like inside. But my 510 really woke up after a baffle was gutted and I installed a exit tube about 2 inches long into the muffler. Stock it did ok had lots of torque for a 49cc but it didn't spin the rpm that is did with a gutted muffler. Just my think outside of the box opinion

 

[David Young]

I will be very surprised if these saws catch a 346. I think the transfer ducts alone are a handicap. They are straight like an open port jug. Its got the funky combustion chamber and even if you get to 15mm that is the size of a stock 346 carb.

but with the long stroke maybe if its chained right....

 

[Miller Mod Saws]

Ok, so similer bore stroke and 1000 rpm less in these echo. Even with roughly the same venturi size. Is that extra 3-5* on the exhaust the 1k loss in rpm vs the stihl?



Thank you, that was the exopxyed intake saw and bored carb?

Hopefully I can get the 14.25 carb to work. To test this theroy.

I know my 346 likes the 16.66 venturi carb.

I don't remember for sure. I can find out I still have the saw. For now!

 

[Red97]

Maybe we are all looking at what is already done and need to look at a different possibility. The MUFFLER MOD. Maybe having a outlet tube in the exhaust with a bigger ID will change results in that. Or a baffle may be causing a restriction to let gasses escape from the port. I don't know what that canister look like inside. But my 510 really woke up after a baffle was gutted and I installed a exit tube about 2 inches long into the muffler. Stock it did ok had lots of torque for a 49cc but it didn't spin the rpm that is did with a gutted muffler. Just my think outside of the box opinion

Empty muffler can on the 490.

I will be very surprised if these saws catch a 346. I think the transfer ducts alone are a handicap. They are straight like an open port jug. Its got the funky combustion chamber and even if you get to 15mm that is the size of a stock 346 carb.

but with the long stroke maybe if its chained right....

Do you think that the stright ducts are limiting the rpm tho?

As for the chamber, yeh not quite sure what they were thinking. Other than the offset helps keep the heat down on the ex side a bit. Why a triangle shape?