Replace Carb Check Valve on CS-590?

[Paul Bunions]

As always after a layoff, my Echo CS-590 refuses to start. I ran it through the sonic cleaner for 50 minutes in gasoline. No help. Checked the plug, too.

I finally decided to see if I could unclog what I thought was a jet. It looks like it was actually a check valve. It's a brass thing that extends into the bore or whatever from the bowl. A black rubber disk popped out of it when I inserted a wire gauge drill bit.

Can this thing be replaced? The part doesn't even appear on parts diagrams.

This carb is really something. Run it dry, it clogs. Use $40 premixed gas, it clogs. I'm thinking I should start pulling the carb and storing it in a jar of gasoline.

I have read that a carb from a CS-620 will also work. Are these carbs any less aggravating?

 

[SteveSr]

As always after a layoff, my Echo CS-590 refuses to start. I ran it through the sonic cleaner for 50 minutes in gasoline. No help. Checked the plug, too.

I finally decided to see if I could unclog what I thought was a jet. It looks like it was actually a check valve. It's a brass thing that extends into the bore or whatever from the bowl. A black rubber disk popped out of it when I inserted a wire gauge drill bit.

That disc is the main nozzle check valve... Main nozzles rarely clog as the hole is too big. Your problems are elsewhere.

Can this thing be replaced? The part doesn't even appear on parts diagrams.

Not easily (assuming that you can even find the part). Now it's replace the carb or try your hand at micro-surgery to put the old valve back in. Saw will NOT run without the check valve.

This carb is really something. Run it dry, it clogs. Use $40 premixed gas, it clogs. I'm thinking I should start pulling the carb and storing it in a jar of gasoline.

Main nozzles rarely clog as the hole is too big. Canned gas won't clog. Running it dry works just as good.

Your problems are elsewhere like an air leak that won't allow the carb to pump fuel, clogged fuel pickup, or a cracked fuel line.

 

[grizz55chev]

That disc is the main nozzle check valve... Main nozzles rarely clog as the hole is too big. Your problems are elsewhere.


Not easily (assuming that you can even find the part). Now it's replace the carb or try your hand at micro-surgery to put the old valve back in. Saw will NOT run without the check valve.


Main nozzles rarely clog as the hole is too big. Canned gas won't clog. Running it dry works just as good.

Your problems are elsewhere like an air leak that won't allow the carb to pump fuel, clogged fuel pickup, or a cracked fuel line.

Low comp will also have an effect on the saws ability to pump fuel, as in weak pulse.

 

[vizette]

Can this thing be replaced? The part doesn't even appear on parts diagrams.

Spend the $8 and save yourself a lot of grief...

https://www.arboristsite.com/threads/echo-590-timberwolf-h-setting.301438/page-6#post-7741275

 

[Paul Bunions]

I appreciate the tip, but it came right after I installed the new CS620 carb. I am trying to tune it right now. Farted a couple of times but didn't take off and run.

 

[vizette]

I appreciate the tip, but it came right after I installed the new CS620 carb. I am trying to tune it right now. Farted a couple of times but didn't take off and run.

Cool, let us know how the 620 carb goes, always good to have options.

 

[ballisticdoughnut]

That check valve can be replaced, I’ve done it on my CS-600P which is basically the same saw. What all have you checked besides the carb and spark plug? I see you swapped in a 620 carb. Is it a original walbro?

 

[Paul Bunions]

I didn't check anything else. I have been down this road before. The new carb works fine.

The new carb is a Walbro. I have not adjusted it yet. I'm a little nervous about trying. I have been known to adjust carbs until they quit working. I have a tachometer, but I have never used it.

I wonder if people could answer a couple of questions.

1. What is the correct torque for the screws holding the cylinder on?

2. What is the correct maximum RPM for this saw? It seems to rev a little higher with the big carb.

That check valve can be replaced, I’ve done it on my CS-600P which is basically the same saw.

What is the part number? Echo doesn't list it as a separate CS-590 part, and other people say it's not available. I would like to fix the old carb to have as a spare.

 

[Paul Bunions]

I found the shop manual online, and it says the correct torque for the cylinder screws is 60-95 inch pounds.

I don't think I understood the advice about the check valve. I am reading the suggested thread. Something about using a valve from a different saw and plugging a hole in the main jet.

 

[ballisticdoughnut]

I didn't check anything else. I have been down this road before. The new carb works fine.

The new carb is a Walbro. I have not adjusted it yet. I'm a little nervous about trying. I have been known to adjust carbs until they quit working. I have a tachometer, but I have never used it.

I wonder if people could answer a couple of questions.

1. What is the correct torque for the screws holding the cylinder on?

2. What is the correct maximum RPM for this saw? It seems to rev a little higher with the big carb.



What is the part number? Echo doesn't list it as a separate CS-590 part, and other people say it's not available. I would like to fix the old carb to have as a spare.

The 590 has a limited coil, max rpm is 12,500. I’ll have to check my notes on a part number for the high speed nozzle.

 

[Paul Bunions]

Thanks for your help.

 

[vizette]

I found the shop manual online, and it says the correct torque for the cylinder screws is 60-95 inch pounds.

I don't think I understood the advice about the check valve. I am reading the suggested thread. Something about using a valve from a different saw and plugging a hole in the main jet.

Replace the existing one with Walbro p/n 86-578-1 or seal the hole in the existing one shut (and adjust H needle accordingly).

 

[SteveSr]

...or seal the hole in the existing one shut (and adjust H needle accordingly).

This is not likely to work as the main flow (75%) goes through the hole in the main jet and only 25% or so goes through the adjustable needle.

The only way to fix this is to use the correct part. The nozzle should be pulled from the metering side to allow a sealing surface for the new nozzle. If you push it through you may make a leak. Also be sure to remove the "H" screw before removing the nozzle.

 

[vizette]

Going to assume at this point we're talking about different things. The thread linked provided pictures and there are also youtube videos on this. Proven fix.