Where can i get a FREE manual for the Homelite trimmer UT 21566

Hi Cherri,
I think this is the manual for your machine. It should tell you all you need to know:
file:///C:/Users/Jim/Downloads/Homelite-String-Trimmer-Parts-Manual-ST200-String-Trimmer-UT-20501-A.pdf

Good Luck!
Jim

Your missing the last digit of the model number.

UT-20788 and UT-20789 uses the UP00608 carburetor which is a ZAMA C1U-H39.

You can find the service manuals here

http://www.mymowerparts.com/pdf/Homelite-Service-and-repair-Manuals/HOMELITE-STRING-TRIMMER-REPAIR-MANUAL-COVERS-100-DIFFERENT-MODELS.pdf

http://www.odref.com/homelite/string-trimmers/ut-20612r.PDF

Remove the Torx screws holding the rear cover on. Then remove the larger Torx screws holding the muffler on to the exhaust port of the cylinder. There will be a gasket there. The spark arrestor will be mounted in the opening to the muffler. You can scrape or burn the carbon off of it. If the spark arrestor is real clogged up, then the muffler probably is too. It should also be cleaned. The inside of the engine probably is carboned up too( if arrestor and muffler are). They all should be cleaned of carbon. It helps the engine perform at its' best and breathe like it needs to.

You can download the trimmer PDF for free here - http://lawnandgarden.manualsonline.com/manuals/mfg/homelite/homelite_trimmer_product_list.html

Not sure exactly what you need out of the manual, but if you are looking for schematics/parts list here is a .pdf document online that has the tiller broken down. Hope it helps.

http://www.ereplacementparts.com/images/homelite/UT-60526.pdf

This is not a homelite manual.....but it seems to cover an edger exactly like the ut-13140...I had the same edger, and eventually found this:
http://southlandpowerequipment.com/images/southland%20product%20info/S-WLE-0799/manual_S-WLE-0799.pdf

type in homelitest and ut number on the trimmer and then search google . maybe

Go to homelite.com then click on service and support, then click order parts then click launch homelite parts catalog, Agree to terms then click continue under model no type in mightylite then find you trimmer in list.