I have an ECHO HC-210e gas trimmer. I had just bought it 2nd hand. I ran it great for about 10 minutes when it suddenly throttled high. I released the gas right away and it died and hasn't started again since despite much effort. Here's what I've done:

-I verfied spark at the plug by pulling the plug while maintaining connection, holding the hex area to the cylinder wall, pulling the start and observing sparks at the business area of the plug

-I verified gas getting to the cylinder by removing the spark plug and being able to sling liquid off it (I had just done multiple pulls with the throttle fully pulled)

-I replaced the diaphram, metering valve, lever and spring (items 4,5,7,8,9,10,26, & 27 in linked diagram-see below:)

See this link for the diagram and a troubleshooting chart for the trimmer http://diy.stackexchange.com/questions/6640/trouble-starting-my-gas-hedge-trimmer

I assume that the "high tension cord end" is the connector at the spark plug. I'm not exactly sure how to test that. I pulled the plug cap and held it close while pulling the start, but observed no spark. Can someone confirm how to perform that particular check, or confirm that it is unnecessary because I found spark at the plug electrode?

Also, can anyone give me anymore guidance? Of the 100's of pulls I've done since the original incident, I never one time got a single fire from the engine despite every possible choke configuration and lean or heavy throttling.

By the way, while changing the parts I listed above, I thoroughly cleaned the carb.