Fuel starvation at idle?

[WoodShed]

Hello everybody. I'm new to the madness.

Alright, I have a Echo CS-620p (HDA - 316) that has ran flawless since I bought it. I've had it for a year now and decided to do a base gasket delete and polish the exhaust port.

It has tuned well in the cut and at idle with good response. The only problem is after about 10-20 seconds at idle it starves for fuel. It idles up, surges, then dies. If I give it a couple blips when it idles up, as running out of fuel, it will lean bog, but fill the carb back up with fuel and idle for another 10 seconds or so again....repeat. Otherwise it runs perfect. It's like a 10sec timer from the last time you touch the throttle.

It seems the carb is not pulling fuel at idle.

What would cause the carb not to fill at idle?

 

[cus_deluxe]

And it runs normally at WOT amd under load?

 

[WoodShed]

Yes.

Clean in the cut and light 4 stroke when lifting. And the idle is perfect for about 10-15 seconds, with good response.

Also if I let it die at idle it will some times take the choke to prime the system to restart.

 

[Mastermind]

That carb is a weird sob.

@Red97

 

[Mastermind]

In this thread there is some excellent carb talk.....

http://opeforum.com/threads/echo-cs-590-600-620-porting-mod-build-thread.1638/

 

[WoodShed]

Thanks.

That's a lot of good information.

It actually runs amazing. It just has a 10 second idle timer.

10 seconds to clear the wood out of the way for the next cut makes me work up a sweat, but I suppose it's efficient!

I ran two tanks through it yesterday in hopes that it would improve and once or twice it continually idled. So I guess there is hope.

 

[tree monkey]

pump side diaphragm is too stiff, put an oem hda-24 kit in it using the tan diaphragm.

 

[WoodShed]

I'll give this a try!!!

I did seem a little rigid.

 

[Al Smith]

If,and forgot,that carb has little slot in the butterfly it has to line up with the idle jet .If it's off just an RCH it won't idle right .Been there,fumbled with that .

 

[Red97]

Welcome to ope.

Try 1/4-1/2 turn out on the L screw.

Then kit as Tree monkey suggested.

From my experience these saws like to be rich on the low side.

If you open the L needle you will have to check and likely lean the H needle a bit.

These carbs have very goofy needle settings. Once set right it may load up slightly, but idles tank after tank...

 

[WoodShed]

Welcome to ope.

Try 1/4-1/2 turn out on the L screw.

Then kit as Tree monkey suggested.

From my experience these saws like to be rich on the low side.

If you open the L needle you will have to check and likely lean the H needle a bit.

These carbs have very goofy needle settings. Once set right it may load up slightly, but idles tank after tank...

Thanks.

I fattened the L up a 1/4 turn and it seemed to help. Any more and it would drown it's self out.

It will run much longer now, but gets in this barely running, loping kind of idle.

I plan on picking up a HDA-24 pump diaphragm tomorrow as Tree Monkey suggested and give that a try. Fingers crossed!!

 

[Red97]

Thanks.

I fattened the L up a 1/4 turn and it seemed to help. Any more and it would drown it's self out.

It will run much longer now, but gets in this barely running, loping kind of idle.

I plan on picking up a HDA-24 pump diaphragm tomorrow as Tree Monkey suggested and give that a try. Fingers crossed!!

How did the high side tune out? If it is plenty rich, you could go 1/16 turn in on the H and that will lean the low ever so slightly. To help with the loading up.

These carbs are kind of a dance to get just right. You have the limiter tabs pulled?

A new kit is never a bad thing. But only being a year old, thinking the mods threw the tune way off.

 

[WoodShed]

Yes the tabs are pulled.

The H side is a little rich, but I didn't want to mess with it until I can get it in some wood.

The mods definitely threw the tune off. I believe the L side is out 2.25 turns now. Is that about right?

I'll throw the other kit at it and see what happens.

 

[Red97]

Yes the tabs are pulled.

The H side is a little rich, but I didn't want to mess with it until I can get it in some wood.

The mods definitely threw the tune off. I believe the L side is out 2.25 turns now. Is that about right?

I'll throw the other kit at it and see what happens.

I haven't counted the turn out on the low side. But from feel that doesn't seem too far off.

I do know the H won't be far from 1 turn. Likely be less.

Once you get the kit in report back.

 

[Poleman]

I found that when I get the L tuned to where I like it the H is almost shut or 1/8 to 1/4 turn. This is on a stock unmodified carb like you have. The L & H share a common feed and that's why the L will affect the H tune. To richen it like it needs the H will be close to being closed. Just a tip on what I've found.
On a modified carb you can get more separation between the L & H circuits and adjustability is better also the H is not as rich (which is the reason for modding, or one of them) so the H can be tuned on a ported saw to get it in the desired RPM range.

 

[WoodShed]

Alright...

I had to order the carb kit, so it will be a few more days before I can try that.

I did get it out and attempted tuning it better. I got it closer, but it still goes lean after several seconds at idle.

I've chased the L all over the place with the idle screw.

A picture is worth a thousand words.

Notice how it goes lean at the end after a good idle.

 

[WoodShed]

If,and forgot,that carb has little slot in the butterfly it has to line up with the idle jet .If it's off just an RCH it won't idle right .Been there,fumbled with that .

I checked and the hole is lined up with the notch.

 

[tree monkey]

your vid is private

 

[WoodShed]

your vid is private

Thanks.

Should be able to see now.

 

[Red97]

Hmm,

Ive had 5 or so 590's some of them fought me, but nothing like that.

Can't say for certain. Possible air leak.? Check the impulse hose for nicks/holes.
What did you use to seal the jug?

I Don't touch the idle screw, maybe just set it a bit high until I get the low close. Fix the idle then check the H tune.

Saw didn't do that before your mods?