Porting an Echo 355T

[Nate6421]

I thought I heard somewhere why the 355t sometimes goes a bit lean coming down from idle. I had one do it, then it stopped. Many saws will get somewhat lean at half throttle. The carb might just need a different main nozzle if it is using the thin black rubber check valve that also causes many 590's to have lean idle problems.

Do you know where I would be able to get a check valve? and how I would know which size?

 

[Nutball]

I'm not a carb expert, so you should start a new thread about finding a better check valve/ main nozzle for your carb, and someone else will point you in the right direction.

 

[EFSM]

The mid is always lean, I can get the idle great, and top great, mid is always lean.

Aside from the lean mid, the saw runs great if you are comfortable with the chain takings a couple seconds to come down to a stop. Which I want to fix.

I thought I heard somewhere why the 355t sometimes goes a bit lean coming down from idle. I had one do it, then it stopped. Many saws will get somewhat lean at half throttle. The carb might just need a different main nozzle if it is using the thin black rubber check valve that also causes many 590's to have lean idle problems.

Maybe you all know this already, but Echo changed the 355 air filters to a mesh style filter. They run like a totally different machine and idle/rev up and down way better as well as more power. The paper filter was far too restrictive because it would suck in against the anti-spit plate.

 

[Nutball]

I don't think it's a filter problem. I think it's an air leak problem either caused by a bad carb design, or improper porting or engine assembly.

 

[Nate6421]

I don't think it's a filter problem. I think it's an air leak problem either caused by a bad carb design, or improper porting or engine assembly.

I didn't do all the work at once, the first thing I did was the port matching and rounding sharp angles in the muffler (no extra outlet) and popped the limiter caps. Its had the issue since then. Also, when I did do the exhaust port work, I cheated and didn't disassemble it, just stuffed a rag above the piston, then blew it out well, so its not from improper assemble.


I believe its bellhopper on YT who did a couple videos porting a 355t and had the same issue with a lean mid.

 

[EFSM]

I don't think it's a filter problem. I think it's an air leak problem either caused by a bad carb design, or improper porting or engine assembly.

You may be right, especially if this is a high use saw. However, I had a nearly-new 355 that was running similar to what's being described here, and the updated filter fixed it. I chased that issue for hours before figuring out what was going on.

 

[Ketchup]

Check your intake boot. I’ve had problems there in a variety of Echoes.