Craftsman parts 172.745440 same as

Remove string cap and tighten nut or you will have to hold shaft just above string head with pliers and turn head by hand till tight.
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Craftsman 17 25cc Weedwacker

Once you remove the spool cap and the spool, you cannot remove the head from the motor. It is not a replacement part.
Ryobi P2002 Cordless String Trimmer Parts

remove the housing that holds the recoil and whined up the spool and thread in a new rope

You should check the filter inside. It sounds like it is dirty and it is causing the vac to overheat.

Jim

Spring, spool then cap....if that way doesn't let the line out correctly, then it is possible you have wound the line on the spool in the wrong direction. Try taking the line off and winding it on the other way.

take off knob that holds on the spool on bottom of weedwacker, remove spool, there are notches around the outside splines on the bottom of the spool. (the bottom is the end that fits up into the spool housing. there are 2 little holes opposite one another on the spool - one on each section. Cut two lengths of line about 6 feet long. stick line into first hole (near bottom of unit) wrap line around spool. once wrapped line gets short - to the point where you cant wrap it anymore - stick the end into one of the notches - do the same with the other line - insert spool back into housing - make sure spring is attached to the spool and lines come out of the holes in the housing - reinsert knob and tighten - make sure as you are doing this you unseat the ends of the lines off of the notches on the spool and they are out through the housing - tighten knob and you should be good to go

go to sears.com, where they have all craftsman parts for their items less than ten years old.

You can either go to sears, or craftsman website or even easier if you can get one off of ebay

could have been caused by any number of thing's,
take the recoil assembly off and try pulling the rope out while holding the center of the rope spool just enuff to prevent it from popping out in case there's nothing holding it there.
rewinding the rope is alot easier than rewinding the recoil spring Trust Me.. lol