Echo SRM-3000 running issues

[tubpilot]

I just got a very low hour Echo SRM-3000 trimmer from my sister, it started up fine, but surged at full throttle. I traced the surging down to a cracked fuel line. Now it'll start up and run great until it gets warm (less than 5 minutes). Once it's warm it won't take throttle, and the idle is unstable. I figured there might have been some damage from leaning it out with the cracked fuel line, so I pulled the cylinder and there is no damage, I checked and the muffler and sparky screen are clean. I have a gasket kit and carb kit on order and should be in next week. I really think once it's together it's gonna be the same cause I haven't found anything wrong. my question is what should I look at next? Does the coil break down with heat and produce weak spark?
Thanks for your help.

 

[AVB]

Fuel mixture setting can be the problem if set improperly. This is a give-me here on any 2C repair I do; after several years of working on these I just adjust them all now even if they don't seem to need it.

With the fuel being cracked you find a good ultrasonic cleaning of the carburetor including replacing the internal screen filter in the carburetor will fix most fuel related problems as trash may have been suck in through the cracks.

As for can an electronic coil fail when it gets warm, the answer is yes. Just last fall I had John Deere (Homelite) that would only idle and if you try to accelerate to full throttle is would sometimes backfire through the carburetor along coughing and sneezing. After trying several things I ended up putting on a new coil which fix the problem.