Echo cs 490 porting

[Red97]

044 carb HD something, knock off from ddave. It's identical internally to an HD 18 from an 029, but with a larger bore

Inlet
View attachment 17135

Venturi
View attachment 17137

I didn't get the throttle bore size, as it's still on the saw

Thank you sir.

That may be a bit on the large size for what I am after.

I'm thinking 19mm bores and 16.6 venturi would be ideal for this echo. Same as the hda 198/9 that works so well on the 346's.

Since I have a hda198 at home, I plan on trying to replicate it in a wt body...

 

[huskihl]

Thank you sir.

That may be a bit on the large size for what I am after.

I'm thinking 19mm bores and 16.6 venturi would be ideal for this echo. Same as the hda 198/9 that works so well on the 346's.

Since I have a hda198 at home, I plan on trying to replicate it in a wt body...

I actually think the carb from an 029/039 might be a better candidate in an 026. A couple mm shy of the 044 carb all around might get rid of the idle problems associated with this swap

 

[David Young]

What model carb is on there Joe

 

[Red97]

What model carb is on there Joe

Wt 1009

15.8xx bore 13.5 venturi
Largest walbro wt venturi is 14.25 got 3 waiting for me to play with

And a zama c1s which is the walbro wt equivalent
With 16mm bore and 14.6 venturi. Have 3 of those to play with as well.
The zama will be almost ideal. With one I plan on boring to c3 el32 specs, 17mm bore and 15.xx venturi. Stock 346 carb.

 

[Stihlbro]

 

[Red97]

I actually think the carb from an 029/039 might be a better candidate in an 026. A couple mm shy of the 044 carb all around might get rid of the idle problems associated with this swap

Walbro Hd5, I'm sure their is a zama one too.

I think you are right. Bigger isn't always better. It is about matching everything to work together, will make the best all around saw.

 

[Stihlbro]

It looks to be a governored factory carb.

 

[huskihl]

Walbro Hd5, I'm sure their is a zama one too.

I think you are right. Bigger isn't always better. It is about matching everything to work together, will make the best all around saw.

The one off the 029 I looked at tonight was I think an HD 18 or 19. But probably similar to hd5

 

[Stihlbro]

Can't get my fingers to work right on my phone, but the item descriptions show 3 different options on the main nozzle feeder.

This is from the actual walbro pdf of the Wt1009.

 

[paragonbuilder]

View attachment 17154

It looks to be a governored factory carb.

Please share how you know this from this diagram.
Thanks Joey,
Dan

 

[Stihlbro]

The picture does not show, it's in the parts description. I can't get my phone to get the picture of the item numbers. Working on it........

 

[Stihlbro]

Item #22 show different options. The echo version is not this descriptive.

 

[CoreyB]

I finally got to watch some of the videos. Nice job on those 490'same guys. Looks like a fun little saw.

 

[wigglesworth]

@wigglesworth can you explain this.
I talked this over with wiggs and he tried to explain it. He didn't have the carb in hand of course. But it's something to do with the carb having dual feeders to the high side so it's actually governed.

I'm late to the party...

With the high needle closed off, and it's still getting too much fuel, it could be a couple things. First thing, check and make sure your lever is set right. Then, make sure your needle sealing off.

If those are right, u need to find the primary feeder circuit, which is usually a pressed in or sometimes screwed in jet that feeds the high side nozzle independent of the high side screw.

It could need closed off some. If they are pressed in, then about the only option to closing them up is to solder them closed or peen them closed and drill a smaller hole. I've never successfully removed a pressed in jet without destroying it.

If it's screwed in, walbro offers different sized jets to install. But it's a bear finding the right part number....

It's pretty easy to seal them off, and enlarge the screw metered circuit, which will basically convert it over to the old school high side control. That's how I typically do it.

Clear as mud?

 

[Miller Mod Saws]

I'm late to the party...

With the high needle closed off, and it's still getting too much fuel, it could be a couple things. First thing, check and make sure your lever is set right. Then, make sure your needle sealing off.

If those are right, u need to find the primary feeder circuit, which is usually a pressed in or sometimes screwed in jet that feeds the high side nozzle independent of the high side screw.

It could need closed off some. If they are pressed in, then about the only option to closing them up is to solder them closed or peen them closed and drill a smaller hole. I've never successfully removed a pressed in jet without destroying it.

If it's screwed in, walbro offers different sized jets to install. But it's a bear finding the right part number....

It's pretty easy to seal them off, and enlarge the screw metered circuit, which will basically convert it over to the old school high side control. That's how I typically do it.

Clear as mud?

Hi buddy! Thank you!

 

[Red97]

I'm late to the party...

With the high needle closed off, and it's still getting too much fuel, it could be a couple things. First thing, check and make sure your lever is set right. Then, make sure your needle sealing off.

If those are right, u need to find the primary feeder circuit, which is usually a pressed in or sometimes screwed in jet that feeds the high side nozzle independent of the high side screw.

It could need closed off some. If they are pressed in, then about the only option to closing them up is to solder them closed or peen them closed and drill a smaller hole. I've never successfully removed a pressed in jet without destroying it.

If it's screwed in, walbro offers different sized jets to install. But it's a bear finding the right part number....

It's pretty easy to seal them off, and enlarge the screw metered circuit, which will basically convert it over to the old school high side control. That's how I typically do it.

Clear as mud?

Better late than never.

Thank you for the advice.

 

[drf256]

Red,

I'm really think t that opening the Venturi to 15mm here alone may be the ticket.

It should create a lower vacuum signal and pull less fuel out of the main nozzle.

I haven't measured yet, but the coveted 262 Walbro 87 carb has a nearly non-existent Venturi. By eye, I'd say 1mm or less. I need to measure it.

I had to put my glasses on to even see it.

 

[Red97]

Possibly, but isn't the hda 87 a 19mm bore?

I think the choke rod/butterfly is the big restrictions in the stock carb.

Plus the governed passage.

I need to wait until i get back to actually compare the carbs in hand vs looking at pictures / specs. To make any conclusion

 

[bikemike]

running alright think it needs a tad more fuel

 

[Red97]

running alright think it needs a tad more fuel

Looks like it is running pretty well.

You done anything with the port timing?