My 2 stroke unit hasn't done that and I think the shafts are the same. I've leaned in on the edger a little harder than I should have a few times but no problems. The 4 stroke is supposed to have more torque and maybe the shaft just isn't up to it. If you don't mind me asking, your shafts break after a few hours of doing what? Just weeding?

the ryobi was notorius for the shafts breaking if you use anything other than the original string head. are you using the aftermarket plastic cutter blades? if so this puts extra torque on the shaft.

Nope! the last one only weedate with .085 string. I would estimate it takes 20 to 30 hours of use before it wades up the cable and it soon breaks. I think is unwinding at the upper end cause they all break at the upper coupler at the clutch. I have about all the attachments for this, but rarely use them. I would think the edger would be the hardest on the cable????

Thinking about making me a up shaft out of square stock with two bearing inside the tubes. Beings I got 5 sets of ends and tubes to work with. Probably just tranlate it to the bottom cable, but the bottom cable is about 5 bucks and can be replaced with having to buy the tube.

Completely replaced and rebuilt the upper shaft and lower shaft, lower head, and the clutch. We'll see how long it last's. Worked good tonight. When I took the bottom head apart found a bunch of weeds wound around the shaft on the inside. Could caused it to drag some putting more pressure on the upper cable. Sure free wheels now. I got out bid on upper shaft assy on ebay. I wasn't going to give more than a new one when you include shipping.