I have ordered Homelite 25cc Parts from http://www.outdoordistributors.com/H...rts-lists.html with good success. You can search through the proper Service guides from there if you know the UT Number of your string trimmer. All of the string trimmer motors that I have cross reference to the same part number of HOM-PS01359. The stock ring will probably cost you more than ordering a ring from Frank if you consider the cost of shipping to Canada.

The indicators that you can check for are lack of power, low compression. For me I have gotten away with a visual check through the exhaust port. I usually check for heavy carbon buildup which would indicate to me that there may be a lot of carbon in the ring groove which could prevent the ring from expanding to fit the cylinder properly. I have had 5 motors with stuck rings of the 12 that I have tinkered with. I usually put everything (Cylinder and piston) in a crock pot antifreeze bath over night to loosen up the carbon and clean everything up. I ended up having to break the ring on 2 of the 5 motors even after the antifreeze bath to get the rings out of them. Make sure that you are using the proper gas/oil mix so that the engine does not carbon up again.