Clogged exhaust screen, muffler or port. I know the sound.

 

Yeah, that is exactly what I think it sounds like too. But I took the muffler apart and the screen looks almost new. I took the muffler completely off and ran it and of course it sounded a bit different but it behaved the same way and wouldn't accelerate.

 

You have to remove the screen, the backside is what gets carbon build-up.
Many Echo units have a catalytic muffler, so that could be restricted.
And of course, look at the baffle holes for plugging if not a cat-muffler.
I've seen baffles break and cause restrictions as well.

 

I completely took the muffler apart. Referring to the attached image, I took F35, F34 and the screen F32 off and it was very clean and not clogged at all. Then I looked into F27 (the main muffler) and the baffle in there seemed to be clear. I could see light coming through it and could blow through it with little restriction and it looked very clean as well. I then ran the engine with the entire muffler (F27, F32, F34, F35) removed. With that removed I am looking directly in at the side of the piston through the exhaust port in the head so there can be no obstruction on the exhaust side. It ran exactly the same. I know 2T engines do not run their best with the muffler removed, but it really didn't change anything in regards to how it was running and lack of acceleration.

What is odd about this too is how 5 or 6 times it would run perfectly for a few minutes and then instantly start running badly. I would take it apart for inspection and put it back together and it would run fine for 5-10 minutes again, then start running bad. Then the ignition seemed to die and I replaced it, and then I had the same experience with it running fine for 5-10 minutes, then suddenly it would start running like in the video. It made me think it was something heat related. But now no matter how long I let it cool, it constantly runs like that.

I have an echo string trimmer with the same engine but many of the parts (like carb and muffler) are different. It runs fine. I'm wondering if it would be a good idea to put the muffler from the string trimmer on to the blower for a few minutes to see if it makes a difference. It is a different part number but the attachment to the engine appears to be identical.

 

Hmm...I listened to the vid again, that's plugged exhaust. Fair amount of intake noise, but no increase in exhaust noise.
There's an outside chance the flywheel key is bent or sheared. I'm betting against that though.

 

I saw where someone had this same issue with a Stihl (ran well when cold then would bog down when hot) and they had a bad crank oil seal that was causing the problem. Mine was doing that but now bogs down all the time even when cold. Anyway I had the flywheel off tonight to view the seal (and it looked fine) and the flywheel key was fine as well.

I have some pictures of the screen, the exhaust port of the engine with the muffler removed, and looking into the muffler output (where the spark screen sits). You can't tell much from the picture of the muffler baffle, but it looks clean and when I shine a line on the output side, I can see the light through the baffle on the input side. And when I blow 10 psi air through the input, it comes out the exhaust and there doesn't appear to be anything clogging it.

 

OK, I re-read your next-to-last post. It runs fine at times, then it doesn't? Rare, but...I've seen a somewhat similar situation on Stihl FS/FCS units with a variable timing ign. coil that is doesn't always advance the timing on throttle-up. It usually wasn't a constant problem, rather sporadic. Similar sound, but more like laboring above idle than a held-back sound as is with plugged exhaust. Also they'll often achieve an rpm about double idle but no more.
As for a seal or gasket leak, those produce different symptoms in most cases. You could perform a crankcase pressure/vacuum test to eliminate that aspect.

 

Well it would run for 5-10 minutes just fine, then suddenly start bogging down. Then maybe an hour or so later it would run ok again for 5-10 minutes. However a few weeks ago when I replaced the ignition coil it ran ok for 5-10 minutes then started bogging down, and since then it has never run ok even when cold.

I have a leak down test kit for cars, but I would have to rig something up to block off the exhaust and intake ports.

 

Well it would run for 5-10 minutes just fine, then suddenly start bogging down. Then maybe an hour or so later it would run ok again for 5-10 minutes. However a few weeks ago when I replaced the ignition coil it ran ok for 5-10 minutes then started bogging down, and since then it has never run ok even when cold.

I have a leak down test kit for cars, but I would have to rig something up to block off the exhaust and intake ports.

OEM coil, or aftermarket? It obviously doesn't lose spark. A problem is most OPE engines have no provision for us to test timing. Again, it's rare but I have seen it a handful of times. And, not all mfgs. use a timing control system in their coils, many are fixed timing.

A leak-down tester will not adapt to what I was referring to. Crankcase pressure and vacuum tests apply .3 to .5 bar (1 bar = 15 psi). Use of more can blow out a seal. You could search the forums, I've posted a fair amount on this subject over the years.

 

It was an OEM coil. I used an aftermarket one on an old Lawn Boy years and I was able to get it to work, but it was kind of warped and difficult to get the gap set correctly. I learned my lesson there.

I wasn't going to use my leak down tester, just use the adapter hose from that kit that will screw into the spark plug and then connect to a small hand pump with a gauge that I have. I will search through the forum and try to do this test in the next few days. And post back my results. Thanks!

 

Sorry to hear you were down. But hope your fix works on the shredder. 🤙

 

Thank you!

Unfortunately I put it back together and it is running exactly as it did before. I tried adjusting the needle on the carb and that didn't change things at all. I really can't think of anything else to try at this point. I agree with paulr44 that it sounds like a blocked exhaust, but the exhaust is clear and it even runs the same when I completely remove the exhaust. I have a new air filter, fuel filter, carburetor, spark plug and coil. I'm general not one to throw in the towel, but I guess I should just buy a new one.