I have a echo cs305...will start, and run for 10 to 15 seconds

Yes, the air fuel mix screws have adjustment limiter caps to prevent the typical end consumer from maladjusting the carburetor and ruining the engine.

Try calling echo and ask for tech support or go online to get the phone # or check you tube to see if they have a video on it

This appears to be a good news problem. There is an easy fix/work around! Consumer reports found the same problem that you have discovered.

Holding down the check battery switch allows the unit to operate. Read the link around the sixth paragraph the story is told.

Echo Trimmer Can Be Tricky to Start

"Our testers discovered the fix by chance. Pressing the check battery button, a last-ditch attempt to get the trimmer working, made all the difference. While this button ordinarily indicates the battery's charge status, in this case it also served to keep the battery from switching into protection mode and cutting off power to the motor. The next time you fully charge the battery, however, the problem can reoccur."

Hope this has helped?

here you go .enjoy
http://www.echo-usa.com/getattachment/41524bf0-914b-4129-9f2c-e8e39b526de1/CS305

check for problems in the carby--replace with a kit
check the filter on the end of the line in the tank-- they tend to block up
check for blocked exhaust--- carbined up inside
don't use E fuels as they will not operate on the E mix

Toni,
Can you give me a little more information on your problem. Are you having a problem with the throttle linkage or is it a carburetor adjustment question?

The air gap should be .010 not .001

sounds like a dirty carb, dissamble it and rinse good with carb clean, be careful when taking the top off it that you get it back together the same spray the white center good and all little holes good. then reassemble, also try to loosen your gas cap maybe first before cleaning carb, you might have a plugged vent in the line coming out of the tank. Good Luck

more than likely needs a carb kit

50:1 gas/oil mix. To mix 1 gallon of gas, you need to add 2.6 fluid ounces of two-stroke air-cooled oil to 1 gallon of gasoline. Higher octane works better and runs cleaner.

Assuming you have a CS305, here's the user's manual.

If this helped, please give it a vote.