The 4 most common part(s) or condition(s) which contribute to the symptom String trimmer head won't spin are listed below. Check or test each item and watch any available videos. If you are still unable to solve the problem you may need to do additional research and troubleshooting. Remember, with our 365 Days. Period.® return policy you can return any part for any reason. So, go ahead and buy it to try it. No other parts retailer offers this unconditional return policy.
For the symptom you selected, these are the most common parts or causes, ordered by the likelihood of fixing the symptom.
If the string trimmer head won't spin the clutch assembly might be worn out. The clutch assembly is located near the engine at the end of the trimmer shaft. It is sometimes possible to clean and repair the clutch assembly, but given the relatively low cost and the difficulty of the repair, it may be easier to simply replace the entire clutch assembly.
If the string trimmer head won't spin the drive shaft might be broken. The drive shaft is a long, flexible shaft which connects the clutch to the trimmer head. The shaft spins inside the trimmer tube at the same speed as the head. Over time the shaft can wear out and break. It's not possible to repair it. If the drive shaft has broken it will need to be replaced.
If the string trimmer head won't spin the head may have separated from the drive shaft. Disassemble the head to determine the cause.
If the string trimmer head won't spin the throttle cable might be broken. The throttle cable connects the throttle trigger to the carburetor.