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Trimmer Stringhead Not Spinning

2856 Views 3 Replies 3 Participants Last post by  hankster
I have a 2 year old straight shaft Homelite trimmer (model UT20811B0) that was manufactured by John Deere. It's powered by a 2 cycle engine. I was using it as normal and the stringhead started spinning very slowly and could not cut through the grass. I cleaned the sponge air filter, put in a new spark plug and the engine was still running rough and the stringhead did not spin at all. I even bought fresh gas and a new bottle of 2 cycle oil (50:1).

Any ideas what the problem can be and is there something I need to check? If it is something I can repair, where can I get parts?

I don't think it would be worth bringing it to a repair shop, because they would probably charge me what it would cost to purchase a new trimmer. I appreciate the help and thanks for participating in a supporting website like this.
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possible clutch problem- string head where the drive cord runns thru could be spun out- possible drive flex shaft broken or wore out. seperate engine from shaft , inspect & diagnose. alot of rough runners can be fixed by a simple carb adjustment. let us know what ya find .
Doctorslotcar, this is one of those trimmers where you can add attachements. We disconnected the shaft with the stringhead and put it on a Ryobi trimmer and it worked fine. I was planning to separate the engine from the shaft and see if there is any rotation at all. As far as the engine running rough; after reading some of the threads, it sounds like it's possible the carb needs some cleaning. I noticed Hankster mentioned in another thread they are difficult to get to and check to see if the strainer in the tank is plugged. Thanks, and I'll keep everyone posted.
I haven't worked on that model but the main failure point on "two piece" shaft trimmers is the coupler in the top flex shaft (that the bottom flex shaft fits into) gets stripped. Depending in the model you can just replace the upper flex shaft or you may have to replace the complete upper shaft.

Other points of failure is the clutch bell gets rounded out where the upper flex shaft fits into. It could also be the plastic insert inside the shaft tube (that the flex shaft rides in) becomes melted or shifts allowing the flex shaft to move up or down within the tube and lastly, the flex shaft itself can break.

First look carefully at the coupling in the upper flex shaft and see if there are any signs of rounding off or wear.

Disconnect the attachment, insert a screw driver tightly into the coupling in the top flex shaft and carefully start the engine. Hold on to the screw driver and slowly increase the RPM. You should feel the shaft try to rotate. If you hold onto the screwdriver firmly so it won't turn you should be able to really be able to load down the engine. If the engine freely revs it is either a bad clutch bell or the plastic inner sleeve is melted or shifted.

Now pull the shaft out (using the tightly jammed in screwdriver) and try and rev the engine. If it now easily revs it most likely is the inner plastic sleeve.

Two piece shafts can be a real pain. Some have so little engagement in the clutch bell, between the shafts and the gearbox that any shifting of any of the shafts disengages them. Your symptom of running slowly before it stopped working makes me think it is more likely a stripped coupling or stripped clutch bell. Whatever the case, it can be fairly expensive to fix.... by their pricing, Homelite must be pretty proud of their products ;)
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