New wife has cc4125. How do you replace trim wire

Your battery sounds like it has failed internally. If it is older than 5 or 6 years, you need a new one.

It sounds like the carb needs adjusted. Things can even happen to new weed eaters.

on your weed eater there should be a lil bubble looking thing called the primer somewhere around tht should be a black box with a screw of some sort on it take the lid to the black box of and theres your air filter

Believe you may have bad gears in item no. 17 would try replacing. To see this diagram go to partstree.com type in your model no. etc.

I didn't find that exact one either, but recently had to work on my Yard Man 4-Cycle Straight Shaft and used a Troy-Bilt manual for a similar trimmer - worked great.
If you don't find yours at this site, maybe a similar one will work. It looks like the difference is the TB525 receives attachments. If you're trying to fix something right now, here's the manual for that one until you find yours:
http://lawnandgarden.manualsonline.com/manuals/mfg/troybilt/big_red_tb575ss.html

rotate attatchment head slightly while inserting driveshaft

Replacement head can be purchased from amazon, here Amazon com troy built head. I hope this helped you. Have a nice day. Vince

Sounds as if the line is wound on the spool the wrong way, causing it to want to always feed string.

Jim

Unless it has a tag or decal on it saying it is a 4 cycle then it uses mixed gas/oil at about a 50:1 ratio. Straight gasoline will freeze the piston in the cylinder in mere minutes.

I had a similar problem with my troy-bilt weedeater. I tried replacing the sparkplug, replaced the fuel filter and etc. It still would not start. I looked at the troubleshooting guide in the owner's manual and it listed a possible cause as a clogged spark arrestor. I cleaned out the spark arrestor by taking it off and cleaning it with a wire brush. Now it runs like brand new again. I hope this helps.