I was on ebay purchasing a sprocket bearing because when I was cleaning mine and inspecting everything the bearings fell out of their casing when I took of the sprocket. I just replaced the bearing and sprocket about 18 months ago. Should I consider a new sprocket also. What should I be looking for on the sprocket that would indicate its time. The ebayer I'm buying the bearing from also had this http://cgi.ebay.com/Stihl-MS290-310-390-Spike-Dog-chain-catcher-bumpers-New-/190409347982?pt=US_Chainsaws&hash=item2c5548138e listed. Are those plastic bumpers important. I purchased my saw used and they were never there, didn't know any better. Oops, forgot to say the saw is a stihl 029 super.