CS-590 Floods Instantly When I Try to Start it

[Paul Bunions]

I stuck a 620 carb on my Echo CS-590, and it started fine. I put the saw down because I had an oiling problem, and I was waiting for a part. A few days later, I fixed the oiling system, put the saw back together, didn't mess with the carb, and the saw would not start.

I downloaded the procedure for adjusting a 620 carb, but the saw still would not start, so adjusting it was not possible. I left it at the setting the manual recommended, which was not the setting the carb arrived with.

Today I tried again. I had seen a video saying to pull the cord slowly a couple of times to suck fuel through the carb and never to yank the cord more than twice with the choke on, so I did those things, and the saw farted once but would not start. I put a cable tie on the trigger and started yanking, and the saw ran. I got it adjusted so the idle was right, but that's all I did.

A long time ago, I saw a video saying a flooded saw could be unflooded by holding the trigger down while starting, and that's why I used the cable tie.

My question: what does it mean when a saw will only start with the throttle wide open? Clearly, this saw floods just about instantly when you try to start it.

I guess one or both of the screws (L and H) must be in the wrong position, but I would like to have some clue before I try to adjust them.

 

[SteveSr]

I stuck a 620 carb on my Echo CS-590, and it started fine. I put the saw down because I had an oiling problem, and I was waiting for a part. A few days later, I fixed the oiling system, put the saw back together, didn't mess with the carb, and the saw would not start.

I downloaded the procedure for adjusting a 620 carb, but the saw still would not start, so adjusting it was not possible. I left it at the setting the manual recommended, which was not the setting the carb arrived with.

Today I tried again. I had seen a video saying to pull the cord slowly a couple of times to suck fuel through the carb and never to yank the cord more than twice with the choke on, so I did those things, and the saw farted once but would not start. I put a cable tie on the trigger and started yanking, and the saw ran. I got it adjusted so the idle was right, but that's all I did.

A long time ago, I saw a video saying a flooded saw could be unflooded by holding the trigger down while starting, and that's why I used the cable tie.

My question: what does it mean when a saw will only start with the throttle wide open? Clearly, this saw floods just about instantly when you try to start it.

I guess one or both of the screws (L and H) must be in the wrong position, but I would like to have some clue before I try to adjust them.

You need to pressure test the carb at the fuel inlet. It should hold 7-10 psi indefinitely. If it doesn't you likely have a needle/seat leak that must be found and fixed. Tank vapor pressure will force fuel through the leak and into the motor flooding it.

 

[Paul Bunions]

I should have pointed this out: the carb is a brand new OEM job. It's not very likely that it's damaged or clogged.

I just watched a video by a guy called the Repair Specialist on Youtube, and he showed how the H jet provides the starting fuel and the idle screw just holds the throttle open so fuel gets sucked through the H jet. I think when I start adjusting this thing, I need to reduce the flow from the H jet.

 

[SteveSr]

I should have pointed this out: the carb is a brand new OEM job. It's not very likely that it's damaged or clogged.

I know that I am dating myself... What did Reagan say? Trust but verify.

Saw starts mostly on the "L" circuit. The OEM carb should have been pre-set to stock settings unless you monkeyed with it. If you did go back to the stock settings and try again.

 

[Paul Bunions]

I definitely monkeyed with it, but that was because it had started flooding and couldn't be started. I did the procedure from the manual.

I will look into the L flow tomorrow. Thanks.

 

[Old2stroke]

With the choke closed and the throttle partly open, intake vacuum is presented from the engine end of the carb right back to the choke plate and fuel is sucked form both the idle ports and the main jet, providing a VERY rich mixture. Normally the engine is pulled over with this setting until it coughs and then the choke is kicked off but left in the fast idle setting until the engine fires. The idle adjust screw setting is only good for running idle speed and does not open the throttle enough for good starting, that is done by the throttle being set to the fast idle setting. Regardless of the type of carb or age of the saw, normally after it coughs on full choke, the choke should be opened and the throttle must continue to held partially open until the saw actually starts. If the saw starts without a preliminary cough or won't start unless the choke is kept on, it's important to get the choke off quickly or it could flood.

 

[Paul Bunions]

The video I watched said fuel for starting was sucked in via the main jet, not the low speed jet, so that's why I was concerned about the H screw.

 

[MudgeHollowBeaver]

I should have pointed this out: the carb is a brand new OEM job. It's not very likely that it's damaged or clogged.

I just watched a video by a guy called the Repair Specialist on Youtube, and he showed how the H jet provides the starting fuel and the idle screw just holds the throttle open so fuel gets sucked through the H jet. I think when I start adjusting this thing, I need to reduce the flow from the H jet.

'the idle screw just holds the throttle open'.... that is actually the idle speed adjustment screw. The screw marked 'L' is the low speed mixture adjustment,,,two different functions

 

[Paul Bunions]

Right. That's why I didn't call the idle screw the low speed screw.

 

[coffeebrk]

From what I've seen and read, installing 620 carb on 590 is accompanied by other mods like porting, muffler mod and 620 coil. I've also seen videos describing a connection passage between H & L to avoid overly lean conditions.

 

[Paul Bunions]

My friend just bought a used one (original carb), and he had a lot of trouble. He has found that if he pulls the cord with no choke, it starts with one pull.

 

[CutsThroughKnots]

I stuck a 620 carb on my Echo CS-590, and it started fine. I put the saw down because I had an oiling problem, and I was waiting for a part. A few days later, I fixed the oiling system, put the saw back together, didn't mess with the carb, and the saw would not start.

I downloaded the procedure for adjusting a 620 carb, but the saw still would not start, so adjusting it was not possible. I left it at the setting the manual recommended, which was not the setting the carb arrived with.

Today I tried again. I had seen a video saying to pull the cord slowly a couple of times to suck fuel through the carb and never to yank the cord more than twice with the choke on, so I did those things, and the saw farted once but would not start. I put a cable tie on the trigger and started yanking, and the saw ran. I got it adjusted so the idle was right, but that's all I did.

A long time ago, I saw a video saying a flooded saw could be unflooded by holding the trigger down while starting, and that's why I used the cable tie.

My question: what does it mean when a saw will only start with the throttle wide open? Clearly, this saw floods just about instantly when you try to start it.

I guess one or both of the screws (L and H) must be in the wrong position, but I would like to have some clue before I try to adjust them.

I have a recently acquired 590, low use with original carb. Same starting problem. I hit on this starting routine:

Pull 3X with choke open
Close choke, pull until it pops
Open choke fully and pull again
Should start right away

Can't help with your adjustment question but this has been working for me to get it running.

 

[freeasaburt]

Tinman did a number of videos on an Echo, same type if i'm not mistaken. He also replaced the carb as well as the coil (and later did work on the ports). He had trouble with the saw running very rich and spitting mixture back. Might be useful to check those vids out?

Edit: here's the playlist. Obviously not every video will be useful to you, but there might be some good info.



(if you click the 'watch on youtube' thingy you get to see the playlist on the right).

 

[Farmer_Nate]

Sounds like a coil.

One saw of mine did this, and had a problem you probably don't. It needed a non-resistor spark plug. Saw is too new for this I guess.

 

[guysmiley]

Or you can have my kind of luck and it could be a dead as a doornail spark plug! Always check for spark when you have a overfueling /no start condition.... now if I could only remember that.
I am sure there are plenty of how-tos on here but for me, I have always pulled plug, connected to wire, ground metal side of plug to engine ground and pull cord with switch on and watch for spark. Must be held FIRM or you will get a good bite if the coil is doing its job. Also if no spark before buying parts not a bad idea to disconnect kill switch and retest just in case switch is shorted. (not sure how common that is but always easy to check).

 

[Goofaroo]

Tank vent?

 

[vizette]

Usually with a vent issue the saw will start and run for a bit and then kinda fade off, because it's getting starved for fuel (the vent isn't allowing air in to replace the volume of the missing/used fuel).

What are the needles set at? I would run them all the way in (gently) and then back out 1-1/2 turns, and start there. Don't worry about H at first, get L set first. If you pull the choke out, it will set a "high idle" of sorts, so it holds the throttle part open. You can then push it part way back in which won't full choke it, but keep the high idle. Be careful because it may take off on you. Also, don't try to start it with the choke full on after it pops on choke, you'll probably flood it.

If it's constantly flooding (like gas leaking out the muffler) then it could be something as simple as crap stuck in the float needle seat. I've had that bite me a few times.

Funny that spark plug was mentioned because I was just watching videos/reading about Torch spark plugs being known for being problematic. The lesson being the off-brand plugs aren't worth the $1 you save vs a champion or ngk.

A factory 590 (you mentioned your friend had one) will probably have an issue with the carb eventually where a check valve goes south and causes it to run rich all the time, no matter what the needles are set at. This can be pounded out of the carb body and a non-check valve put back in place. Kinda of leads me to the question, why did you swap carbs to being with?

 

[idiotwithasaw]

I would check the air filter too. I once had an 046 that would start every time without choking it, turned out it was a plugged filter. So if it's plugged and you are choking it , it could flood in my opinion. Take it for what it's worth. But a bad ignition also could do it.

 

[Farmer_Nate]

All previous posts show great and valid causes of OP's symptoms.

Worst flooder I ever had was plug/ignition related.

 

[Goofaroo]

If I understand correctly you have put a carb on your 590 that is designed for a 620. Is that correct or is 620 the model number of the stock carb?

Why the carb change? Was the saw running on the old carb or was it flooding?
Have you tried putting the original carb back on?

Is this “620” carb a known mod for a 590?
Is this an attempt at more power? Are there any other mods performed on this saw?

As you were told 1.5 turns out on both needles is the typical baseline setting. If it’s gonna start it should start at that setting.

If you’ve vacuum tested the carb as suggested and it’s holding the carb is probably good but of course it is an unknown if it is made for a different saw.

Make sure the fuel cap is tight and push the purge bulb a few times and listen for hissing. Also work the purge and then unscrew the fuel cap and see if pressure is released.

Is the spark arrester clean? Are you sure the muffler is clear of obstruction? Exhaust port? Is it possible you have a carb gasket installed with a hole in the wrong orientation?

The problem is right in front of you. It’s a process of elimination. If the saw was running fine until you put the “620” carb on it I would suspect that it might not be compatible.