Bump feed head knob wont free itself because the flexible cable turns with it..troybuilt tb22 oh my god I strin.... is considered profanity, give me a break \

SOURCE: Replacing the bump head on homelite string trimmer

undo the 2 screws on top of the carb. The bulb is part of a 2 piece cap undo that and it fall out.

SOURCE: Homelite strin trimmer head wont rotate

The only way to access the bottom of the metal shaft is to break it. This is fused on at the factory. It sounds like your flexshaft has twisted in two. Remove the flex shaft from the engine end and see if it is in one whole piece or is damaged in someway. If it rotates at the top but doesn't rotate at the string head this is probably the problem. However, Homelite no longer offers just the flex shaft for purchase. You would probably have to purchase the shaft and the tube as a unit.
But if you are saying the spool and string is not turning at the bottom it could be that the cup which holds the string has worn and can not longer be turned by the shaft. Replace the cup that holds the string.
Another possibility is that the shaft have moved forward, away from the engine and just need to be jammed back in, and retightened (the handle grip and the boom clamp).

SOURCE: Stihl FS45 2 cycle string trimmer. Bought in 5/06

Dealer says shaft has broken. Stihl had a problem with some FS45's doing this. They are trying to have it repaired under warranty.

Thanks for the response.

SOURCE: String will not feed when bumped

I've never had any luck with those stupid bump heads. Every time I would refill them, the string would get caught up. They bind up. I finally replaced the bump head with a string head that you place short pieces of string in. They're not perfect either. You have to pre-cut the string to about 9-12 inches in length, and just replace the piece when it's time.

SOURCE: how do u remove the bump feed spool from the bump

Grasp the outer portion of the cutting head in your left hand and turn the inner knob with your right. Depending on model, some bump knobs are threaded and some are post and notch. Use a little spray like wd40 to loosen the mechanism. It may take a firm hand, but the two will separate so that you can reload the line. Consider reloading with the .095 five sided line. It cuts much easier than the round line.