I have an Echo HC-1500 that worked fine when I was a flatlander but now that I live in Reno at 5000 feet, doesn't run worth a crap. I  tore the thing apart ,checked everything, played with the jets, and googled.

I checked with my neighbor, a commercial landscaper, and it seems in  the business these are known as "green machines", they avoid them like the plague. They are designed to run lean but at this altitude, I can only open the throttle %25 before it bogs and dies. One trick they use is to partially choke them, but it doesn't work on mine.

The jets have plastics heads which allow only a fraction of a turn, and I can find no info on the net, including the Echo website. I thought I was buying a quality piece of equipment but didn't know I was getting into this crap.

Does anyone know how I can get this thing to run right without spending another fortune on it?

I think that you got some bad info. If it started running bad at [i]high[/i] altitude, but runs well at [i]low[/i] altitude, then it's actually running too RICH. The higher you go, the less dense the air, the less oxygen the engine gets, so it needs less fuel to run well. Try to find a way to make it run LEANER.

Well, the bottom line is that it runs well at sea level, but not at this altitude where I need it to. One problem is that this carburetor just doesn't allow you the adjustment range to compensate for the difference. I think what you are saying is partially true, in that there is less oxygen, but the lower density air is sucking less gas passing through the carburetor so it throws off the mixture. I'm hoping someone has dealt with this and can help?

Edit: a local shop says I should be able to yank the caps off the jets and be able to adjust it that way.

Your Echo isn't a piece of crap, it suffers from the same problem ALL outdoor power equipment emission rated engines suffer. Your carb is made unadjustable by federal law. Pry off your limiter caps and have a ball. In some states, if you're caught, it will run you $2000.00 Other areas could give a shit. I don't know your laws. Run it too lean, and you cook your engine.

Johnphin is right.  It's the volume of air that controls the amount of fuel.  Less oxygen per volume richens the mixture.
You might check your manual as I'm guessing it says, "This carburetor does not have
acceleration and high speed adjustment needles." somewhere in the carb adjustment area.
IOW, jet adjustment screws only adjust the idle jetting.
Have you checked the spark arrestor screen in the muffler?  Echo has this to say about it.
 
"Unit starts but will not accelerate / no power at full throttle.

All Echo engines are equipped with a spark arrestor screen located in the muffler. If this screen becomes clogged with carbon deposits, the engine may not accelerate properly. Inspect the spark arrestor screen by removing the cylinder/muffler cover. Remove the screws holding the exhaust guide to the muffler body, then the gasket, then the screen. If the screen is clogged or partially clogged, it should be replaced.  If the spark arrestor screen is clear, replace the spark plug.  If problem persists, contact an Echo servicing dealer."

good luck

Thanks for the pointers. I have cleaned and checked everything, plug, flywheel (the manual says it could cause this if dirty), tank vent , exhaust etc. The fuel filter is a chunk of felt and it looks clean. So that leaves the mixture. I guess I'll have to mess with the carb and take my chances. The only thing I might have off is the oil mix down around 32-1 instead of 40 or 50-1.