Husqy 128LD Just Won't Run

[JAK1911]

Hey guys, I've read several threads about problems with 128LDs, but none of them quite match what I've got going on.
To begin with, this was given to me by a friend who had given up on it a couple of years ago. He said it was surging and wouldn't run right.
When I got it, it had been sitting for several years, was dirty, and had broken fuel lines and crap in the tank.
I cleaned it all up, blew everything out, and installed one of those cheap carburetor kits from Amazon, including new carburetor, fuel lines, fuel filter, air filter, gaskets, and spark plug (Savior BPM7E).
The engine pops off readily with the choke on, then at half-choke it will sometimes start and run for a bit, but if I try to open the choke or give it more than just a touch of gas, it just dies.
I removed the spark screen and it looked good, but tried to run it without it, no joy.
Looking into the cylinder through the exhaust port and the spark plug hole, there appeared to be some vertical scoring, but compression felt pretty good on the pull-rope.
Holding the pull-rope and letting the machine dangle, with a half-tank of gas, it will work its way down if I jiggle it a little, but it doesn't just drop.
After trying adjusting the carburetor, starting at 1.25 turns out from seated, same result. Seems to start between 1.25 and 1.5 turns out on both screws, but just a little change on the Low side while running, kills it.
I bought an Amazon compression tester and it reads between 15lbs and 20lbs on this machine and the same on a smaller Echo that runs fine (well, it doesn't quite get up to the RPM I think it should, but it starts and runs), so I'm convinced the compression tester is a piece of crap.
I pulled the jug off of it, and cleaned it up some. There was some carbon and staining on the sides of the piston, with a thick layer of carbon on the top of the piston. I cleaned it all up with a green Scotch Brite pad, removed the ring and cleaned it's slot, then put it all back together, making sure the gaskets and mating area were all clean and flat.
Had a little better luck getting it to keep running on half-choke after that, but still not really running. Never runs more than a minute or two, and usually less than that.
I pulled the new carburetor and used its parts to rebuild the old carburetor, after a good cleaning -- it was a real mess.
That seems to run just a bit better, but not at all good.
The really weird thing I notice is that when I do get it running (which is pretty iffy), it doesn't idle smoothly. It will ramp up like the trigger's being pulled. It has gotten to pretty high RPM, then drops back down, might speed up a little, then slow down, then just die. It really acts like someone is feathering the throttle, but it's just sitting there on the bench.
BTW, the head spins up with the RPMs, and much of this testing has been done with the lower shaft removed. Everything seems to spin freely.
Wife's in town now, going to bring me a new spark plug, as I'm running out of things to try.
Any ideas? I'm particularly confused by the idle speed increasing and decreasing significantly with no input. I don't understand that, but it did it with the new and the old carburetors.
I really need to get this thing working before the weeds swallow us up.
Hoping someone has a silver bullet to cure this mess.
Thanks.

 

[bertsmobile1]

Firstly there is something totally wrong with your readings
Two stroke hand helds should show around 150psi very few will start at secondary compressions under 100 psi
IF it has been sitting for a long while then there is a better than average chance that the crank case seals are leaking.
As you bought the parts & tools of some unknown supplier who sells through Amazon the there is a 90% chance both the repair kit & the compression tester was retrieved from a scrap bin because those readings are so wrong it s not funny
It also seems you have been watching all the wrong You Boob videos as you have instantly attacked the carb without first pressure testing the tank , the carb & the crankcase .
FWIW, the best way to check old hand helds is very clearly shown on a e-Replacement parts video to quickly evaluate if the unit is worth repairing
After that get yourself a Mighty Max pressure / vacuum pump so you can test the primary & secondary pressure tightness of the crankcase & piston rings and the entire fuel system.
Once you have the right gear for doing the job properly then go You Tube and watch Joe Pace who put 3 or 4 of the actual Husqvarna technicians training school videos on You tube.
You would be advised to ferret out all of them and spend some quality time learning the right way
Then toss that rubbish compression tester either in the bin or on evilpay in the hope so idiot will give you good money for it.
While most techs do have compression testers we very rarely ever use them but when we do we have proper ones for small engines which are very expensive .
The tool you really need is a leak down tester and for that you can actually buy the garbage that is sold on Amazon for people who are too lazy to search out proper tools from real tool stores that do not sell junk because even the most crappy ones will do a reasonable job it they don't have too many leaks . And you might take note that before Joe takes a reading he checks his tools for leaks .
That is the sign of a professional who knows how to do a job properly & not a monkey see monkey do reading numbers of a dial that they do not understand .

 

[JAK1911]

Well, after dinner I went out and put the new spark plug in and gave her a shot.
After a bit of fiddling and warming up, it actually let me tweak the carburetor adjustments and smooth out the idle, then get the trigger response and top end sorted out. We're at 5,000 ft. so it's not unusual to need to tweak the carb, but of course this one had already been fiddled with way too much.
It seems to be running great now, which surprises the heck out of me. I'd never have thought a bad, brand new spark plug would present with those symptoms, but I had read threads on here suggesting bad spark plugs as the culprit for all sorts of problems.
There are plenty of weeds to test it on, so it will get a thorough workout tomorrow, and reveal any flaws.
For anyone interested, the OEM plug for the Husqvarna 128LD is a Champion RCJ6Y, but Champion has a new plug they say replaces that one and is supposed to be better. It's the 852ECO. That's what I installed and got it running with.
The refund claim for the defective compression tester has already been filed.
Now to figure out why the little Echo doesn't seem to be spinning up all the way...

 

[Rivets]

Did you check the crankcase seals when you had it apart? The seals on units which have been sitting a long time will dry out and leak. This will cause a lean starting and running condition, which 90% of people believe is a carb problem.

 

[JAK1911]

Field Test Report:
I fired it up ran it in medium density grass and weeds for about 20 minutes and it performed flawlessly.
It required a bit of nursing to get it started and running, but not bad.
After about 15 minutes of full throttle, I paused to move some stuff and it died. Restarting took a little work and finesse on the throttle, but not too bad.
Shortly after the restart, I began hearing a loud, metallic clacking noise from the exhaust side.
Is this "knocking/pinging," you think? A carb adjustment? Or is the engine letting go and preparing to frag me at any moment?
We need to run into town, so it's going to have some time to rest before I get back to it.
Yes, I cleaned and examined the crank case seals while I had it apart. They looked fine and were flexible.
Any suggestions regarding the clacking noise would be appreciated.

 

[bertsmobile1]

That will be something bouncing around in the crankcase and this includes lumps of the piston skirt
Or the big end falling apart .
So either some thing fell in when you had it apart or it is falling apart