I have a string trimmer that had been sitting for a long time, and I thought I would try to get it running. I did the usual: cleaned the fuel tank, replace the fuel lines and filter, replace the carburetor, and fill with fresh gas/oil mix, but still no good. I pulled the engine to look at the piston, and sure enough, the cylinder was pretty scored up. I replaced the short block with a new assembly. The new assembly came with a new spark plug and coil pack. I set the coil spacing with my brass feeler gauge. I verified spark was good at the plug, and the compression built up to about 120 PSI, after 4 or 5 pulls on the recoil rope. Oh, I also verified that my primer bulb circuit was flowing a nice stream of return fuel to the tank. After all this, I am still unable to get this trimmer started. I started with the customary 1 1/2 turns out from seated on the low and high speed jets, but still no signs of life. So, I have spark. I have fuel. I have compression. And . . . the fuel mix that I am using works in my Echo leaf blower. Any thoughts on this?