How do you replace the trimmer head on the Craftsman 27cc trimmer (Model 711170)?

Video links at the bottom of this feedback.
Turn Off the Ignition: Move the ignition switch on the Craftsman trimmer into the "Off" position.
Remove the Starter Assembly Cover: Use a screwdriver to unscrew the starter assembly cover and remove it from the trimmer.
Prepare the New Pull Cord: Cut off the old cord from both the pulley and the starter handle. Dispose of the old cord.
Replace the Pull Cord: Flip the starter cover over and replace the pull cord. Make sure it's securely attached to the pulley.
Reassemble the Starter Assembly: Put the starter assembly cover back in place and secure it with the screws. How to Replace the Pull Cord on a Craftsman Weed Trimmer (youtube.com)

WS 2400 (CMXGTAMDSS27) (41ADSS27793) - Craftsman String Trimmer Parts Lookup with Diagrams ' PartsTree

Carb needs disassembly and complete cleaning and may need new diaphragm as well.

clean air filter or replace--new spark plug

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/david_2f6e03df6c124197

To test the spark you will need a spark plug tester. Put one end of the tester on the spark plug and the other in the plug wire. Pull the cord and see if fire is there. If not you will need to replace the coil.

you need to check and make sure the head is installed right ,, if it is sounds like you need shaft and see whats not turning and replace,, hope this help

Replace head gear box.

I can get you part way there. Remove the spark plug and shove some clean rope in the cylinder to prevent the engine rotating. Take the front housing off to access the clutch assembly, pull off the black plastic cover from the shaft end, and use a torx wrench to loosen the screw in the end of the shaft. After it's loose, the clutch drum will come right off. Unfortunately, I am stuck now trying to get the rest of the clutch assembly off without damaging it.

Hi and welcome to FixYa, I am Kelly.
Craftsman manuals are avalable for all models on this site:

http://www.managemylife.com/mmh/owner_manuals

You must have your model number

Note the model numbers on this page:

http://www.managemylife.com/mmh/owner_manuals/search/product_type.Line%20Trimmers:Weedwackers,%20Gas?query=27cc+Craftsman+trimmer

Once you enter your model number you click on "Get Manual" and then save as to your computer.
Thanks for choosing FixYa,
Kelly

I had the same problem today. Store told me part 71 85740991 would work.
It does not have same shaft to attach. The original has a plastic head which
melts with use and will not work. I feel it is a defective device. They have a replacement part that does work for a while and does the same thing. Sears
should provide a proper head. A higher priced machine has a proper head.
I would like to by the better shaft and head which I think would fit this machine
but am told you can'[t buy. I'm very discouraged with them. Then engine runs fine.

If you find a solution I would like to hear from you. Thank you.