Echo CS-590 doesn't stay running at idle

[thumbtack]

Thanks all. I ordered a new check valve, but in the meantime, I took the H/L caps off and ran carb cleaner through those passages. Put it back together and now have different symptoms.

When starting it up, I turn the choke on and it'll pop first pull. Turn the choke off and pull it and it'll start first or second pull, but it kind of chugs along at a really low speed, not anywhere near the fast idle I'd expect after just turning the choke off. It'll run forever like that (like, it doesn't die or anything, ran it for a few mins). But. Not only is the idle really slow, but also, there's a lot of smoke coming out of the exhaust. And when I click the fast idle off, it dies, but when I run it WOT, it slows down even more from the fast idle speed and it sounds like it's bogging down (you know that "hollow" sound an engine gets when you go WOT before it's ready, like a cold engine or something).

Some other considerations:
1) when I took off the H/L caps, they were both about 2.5 full turns out. This thread says that the number should be closer to 3/4 for L and 1-1/4 for H. It seems to run better with at 3/4 for L and 1-3/4 for H like the thread says. Not sure if this is relevant.

2) I also ran WD40 through the carb and put a drop of 2 stroke oil into the chamber. Part of me wonders if this is what's burning off, but I would think it would all burn off by now?

Do these symptoms help narrow down the issue?

Thanks!

 

[singinwoodwackr]

L screw needs to be out more than 3/4, imo. Start at 1 turn and open it up until it idles faster then back if off a tad. I’ve had some carbs require 2 turns on the L screw.

 

[thumbtack]

OK, thanks.

One other thing I just noticed.... it used to be the case that when I pulled the carb, I would disconnect the gas line and gas would actively flow out, even if the gas line was higher than the tank, like the tank was pressurized in some way. I'd have to cap the gas line or pinch it or something to stop gas from flowing out.

Just pulled the carb again and gas did not flow out. Seems to correlate with these new symptoms, and actually, the sound the saw makes when bogging out sounds a little like it's not getting gas. Tank is about 1/3 full. Is gas supposed to flow out when carb is removed? If so, maybe this is part of my issue.

Thanks

 

[singinwoodwackr]

Yup, that’s how it works. I drain the tank when pulling a carb and the leave the cap cracked open to keep pressure out.

 

[ChasSC]

Some other considerations:
1) when I took off the H/L caps, they were both about 2.5 full turns out. This thread says that the number should be closer to 3/4 for L and 1-1/4 for H. It seems to run better with at 3/4 for L and 1-3/4 for H like the thread says. Not sure if this is relevant.

Factory starting spec in my book is 1-3/4 (L) and 3/4 (H) Sometimes (L) listed as 2

No offense intended, but.....

The one thing I think we all need to know. What is your experience with repairing 2 stroke equipment.

Have you tried a new properly gapped spark plug. BPM-8Y @ .026"
Fresh fuel >89 octane mixed 50:1

Going back to your first post, I realized you said you put it away. Since it wasn't running correctly and you put it away, I have to assume you put it away without running the fuel out of the carb. Also, more than likely based on other post, you did not put any 2-stroke oil in the cylinder. It seriously sounds like your carb is gummed up, and will require soaking at least overnight. I have used mineral spirits for this task.

I have also used PB blaster to clean carbs very effectively. It is also combustible.

I am not trying to be critical. I just hope you are not getting in over your head. At this point I would HIGHLY suggest NOT replacing valve. You are going to replace a valve you don't know how to test.

Have you pressure tested the carb. First thing I do every time I pull a carb. You never mentioned the condition of your metering diaphragm, gaskets needle valve, etc. If you don't own a tester, they are very cheap off amazon.

Lastly, I did the search for you and referenced many threads about your same exact problems. I don't know how many you have read, but many of the questions you are asking are abundantly available. The more you read, the more you learn, not just someone giving you the answers to the questions. It's very hard to diagnose someone's equipment over the internet without all the information.

 

[thumbtack]

Factory starting spec in my book is 1-3/4 (L) and 3/4 (H) Sometimes (L) listed as 2

No offense intended, but.....

The one thing I think we all need to know. What is your experience with repairing 2 stroke equipment.

Have you tried a new properly gapped spark plug. BPM-8Y @ .026"
Fresh fuel >89 octane mixed 50:1

Going back to your first post, I realized you said you put it away. Since it wasn't running correctly and you put it away, I have to assume you put it away without running the fuel out of the carb. Also, more than likely based on other post, you did not put any 2-stroke oil in the cylinder. It seriously sounds like your carb is gummed up, and will require soaking at least overnight. I have used mineral spirits for this task.

I have also used PB blaster to clean carbs very effectively. It is also combustible.

I am not trying to be critical. I just hope you are not getting in over your head. At this point I would HIGHLY suggest NOT replacing valve. You are going to replace a valve you don't know how to test.

Have you pressure tested the carb. First thing I do every time I pull a carb. You never mentioned the condition of your metering diaphragm, gaskets needle valve, etc. If you don't own a tester, they are very cheap off amazon.

Lastly, I did the search for you and referenced many threads about your same exact problems. I don't know how many you have read, but many of the questions you are asking are abundantly available. The more you read, the more you learn, not just someone giving you the answers to the questions. It's very hard to diagnose someone's equipment over the internet without all the information.

Thanks. No offense taken. My experience repairing 2 stroke engines just in general is pretty extensive (ran a moped repair business for about 6 years, have been repairing 2 stroke engines for 20+ years) but... my experience with chainsaws specifically is negligible. Mopeds don't tend to have check valves or H/L screws, so I don't understand those things at all despite being good with 2 strokes as a type of engine.

In terms of your questions, I've tried a new and gapped plug and I'm using fresh canned fuel mix (I'm sure it's over 89 but I can check). At this point, I feel like the carb is probably clean... I've taken everything off and sprayed through all the passages, and gone through with a wire for the tiny ones. I will hold off on replacing the valve.

I have not pressure tested the carb. Diaphram looks good and pliable, gaskets all look like new, needle valve is not worn, etc.

Plus just look at what's been happening today, all of my symptoms seem to be changing rapidly. At this point, I think the next best course of action is to tune the carb and see what I'm working with. I can get it running... okay.... by tweaking the H/L screws and it stopped bogging down (my L screw was indeed too far in, I'm not sure why that other thread said 3/4 turns out was right). So it's definitely possible that by just tuning the carb I can get it back into shape, or at least see what symptoms are present with a tuned carb.

I'll do that in a bit and update everything, thanks again!

 

[ChasSC]

Just sent you a PM with attached document

 

[thumbtack]

Thanks so much! I will look at it now

 

[JoeMay]

If the carb won’t hold a tuning, non musical of course, then you should start searching for an air leak via a pressure/vacuum test. Lots of guidance on this site about how to do that.

 

[thumbtack]

Hi all,
So, I popped on a new carb and it ran great, meaning the issue is 100% in the old carb. I suspect it's just tuned wrong, but now that I have two, I feel like I can strip it down and really clean it and rebuild it properly. Thanks to all for the help!

 

[ChasSC]

Put a new rebuild kit in it this time.

 

[Cliff R]

Hopefully you bought the correct OEM replacement carb or you'll be right back in it. The "knock-off" replacement carbs aren't worth two squirts of duck poop.....FWIW......

 

[thumbtack]

Put a new rebuild kit in it this time.

Will do, thanks!

 

[thumbtack]

Hopefully you bought the correct OEM replacement carb or you'll be right back in it. The "knock-off" replacement carbs aren't worth two squirts of duck poop.....FWIW......

I did I read horror stories about the knock offs so I get a genuine walbro. Thanks!

 

[Cliff R]

Good news. I'd get a genuine Walbro kit and new check valve and rebuild the original for a spare......

 

[ChasSC]

I'm guessing it's the fuel pump diaphragm. Those little tabs get stiff or bent, and it makes sense with the symptoms.