New echo 590 racing at idle

[Jeeptrekker]

Fired up my new 590 after a mm and limiter removal. After I got it warm and idling nice I made some cuts. Got it four stroking, and very
responsive on the trigger, cleaned up nice in the cut but left it a bit rich to help with the break in. Started cutting up some pine logs bout 15" diameter. Was cutting great then it began to race while at idle. Shut saw off and started to look it over and I had lost the deflector on the muffler. Fearing I had toasted my new saw I pulled muffler. Looks good inside piston and walls clean shiny no scoring. Would losing the deflector cause saw to race at idle? Or should I start looking for possible air leaks? Thank you for any help possible.

 

[buttercup]

Have you tried to adjust the idle blend, a little richer perhaps? Doesn't make sense that it's racing perhaps more like an air leak but worth a try perhaps?

 

[Jeeptrekker]

I fattened it up a good bit earlier. I'm from lightly seated bout 1 turn out ccw on the H and bout 3/4 turn on the L. I was cutting good around 7/8 ccw H and 5/8 ccw L before the racing started. I tried turning the I screw way down but that didn't help. It will idle for a few seconds and then just start revving. I will have to investigate more tomorrow and try it again. Going to check carb I put grease around the air filter tube mount before running it but maybe I sucked up some junk?

 

[buttercup]

I fattened it up a good bit earlier. I'm from lightly seated bout 1 turn out ccw on the H and bout 3/4 turn on the L. I was cutting good around 7/8 ccw H and 5/8 ccw L before the racing started. I tried turning the I screw way down but that didn't help. It will idle for a few seconds and then just start revving. I will have to investigate more tomorrow and try it again. Going to check carb I put grease around the air filter tube mount before running it but maybe I sucked up some junk?

The first thing I would do would be to richen the low rpm blend an see what happens, then you can conclude if something is wrong.
I guess usually a too lean low blend would result in hesitating acceleration firstly, but it seems to me from what you describe that the racing started after you messed with the carb or what?
It sounds like an air leak but perhaps it aint that bad.

 

[albert]

I thought they have a limited ignition.
You sure its is 4 stroking rich unloaded or the ignition limiter kicking in?

 

[buttercup]

I thought they have a limited ignition.
You sure its is 4 stroking rich unloaded or the ignition limiter kicking in?

I thought idle means low rpm, you talking about max rpm?
Maybe I got it all wrong... wouldn't be the first time

 

[Jeeptrekker]

After it started to race the first time and I inspected the saw and piston
I replaced the muffler deflector and added an 1/8 of a turn richer to both LandH screws and lowered the Idle screw
It revved up after a few seconds of idling. I have not run it since. I am going to check it over tomorrow for air leaks/ junk in carb/and throttle linkage issues

 

[Jeeptrekker]

That is a possibility...I feel like it was four stroking but maybe I could be hearing the limiter. I'm puzzled by this as I had zero issues doing the same modifications and tuning to my 490.

 

[nixon]

I don’t know if this will help . But here are the initial carb setting for the HDA 268a .

Fig.3
5. With 2.5 mm blade screwdriver, turn L and H mixture needles clockwise until lightly seated (Fig.4), then turn out both mixture needles follow- ing turns.
L mixture needle : 2, H mixture needle : 3/4
NOTE: If needles are forced during seating, dam- age to carburetor may occur.
6. Remove air cleaner lid and air filter to expose idle adjust screw and throttle plate. Turn idle adjust screw counterclockwise and set the screw until the tip just contacts the throttle plate. Then turn idle adjust screw 2 3/8 turns clockwise.
It sets up a lot different than most other carbs . The high speed nozzle s drilled with a small orifice so that it will still feed fuel from the metering chamber into the high speed nozzle even with the H needle closed .
If you need more info on it , contact Ray Benson . He is a member here ,and is very willing to share his knowledge with those that need a hand .
Also :
I did have one 590 here doing sort of what you describe ,but intermittently . After a cut, it would race at times . Sometimes it wouldn’t . When it did , hitting the trigger woulmusually ,but not always drop the rpm . In this case , it turned out to be the high speed nozzle ( check valve ) .

 

[Jeeptrekker]

Nixon did the check valve need replacing or junk plugging it up? I put the saw back together this morning and ran it to see if the racing would stop with working the trigger...I had just shut saw off after each time it began to race. After fully warmed I fattened
up the H another 1/4 turn ccw then tuned the L to best idle and then went a tad bit richer to slow the idle a bit. Now I cannot get the saw to race. I'm wondering if my issue is in that check valve you mentioned. Thanks everyone for taking your time to help.

 

[nixon]

Nixon did the check valve need replacing or junk plugging it up? I put the saw back together this morning and ran it to see if the racing would stop with working the trigger...I had just shut saw off after each time it began to race. After fully warmed I fattened
up the H another 1/4 turn ccw then tuned the L to best idle and then went a tad bit richer to slow the idle a bit. Now I cannot get the saw to race. I'm wondering if my issue is in that check valve you mentioned. Thanks everyone for taking your time to help.

Unfortunately you can’t get the check valve from walbro . So, it’s basically buy a carb . I found the bad check valve when I cleaned and rebuilt the original . When I cleaned the carb body in a jar of seafoam that I put in the ultra sonic cleaner , the check valve disc just floated out of the carb body . Being as I couldn’t prove it was the problem with the saw . I bought the guy a new carb . Which works fine ... I kept the old carb ,and put a check valve from a HDA 199 in it .
Waiting on a 590 to cross the bench to try it in . ( with owners permission . )

 

[Jeeptrekker]

Oh that's always the way of it... I'm going to do some test cuts later and see if it happens again. Hopefully it was just something I did in the tuning. I let it run for 10 minutes and cautiously revved it up a few times after I tuned it again this morning but didn't get a chance to cut anything. If it keeps happening maybe I'll have to talk to you about trying that carb you have out. It's frustrating because this saw was cutting so well and is quite impressive...thank you again.

 

[sawfixer]

You can get the Walbro PN 86-578-1 high speed jet on Amazon for $5.99/free shipping which will give you full adjustment on the Walbro HDA-268 carburetor. I attempted the fix the rich high speed jet of the HDA-268 carburetor on my CS600P, which I couldn't lean out when I moved from an altitude of 600 feet to 4,200 feet and ran way too rich with the jet fully seated. I also couldn't drive out the existing semi-fixed high speed jet, no matter how much force I applied with a flat punch and damaged the choke shaft. I ended up using a punch to close the orifice and finally was able to lean out the saw to the point where it would tune properly after turning out the jet 1.5 turns from the fully seated position. I recommend this carburetor modification to anyone who performs a muffler mod to an Echo CS590/CS600 and/or lives at a high altitude.

 

[Jeeptrekker]

Finally got some decent weather to get outside and mess with the 590 some more. I don't have any logs at the moment but my gf wanted some stumps dealt with so I dialed the carb in a little more as I cut the centers out of them for burning and took a nice cookie off one to level it for a flower pot or something she wants to put on it. It cut strong and no more racing at idle. I'm more than happy with this saw and excited to see how strong it is once it's broke in. Thanks again for all your help.