I agree w MFL , it has caused broken rings/collapsed lands and I am still in shock from the extensive broken rings thread of several days ago. you can rent a ridge reamer for cheap and the trick is to expand it out just the right amt (not too tight) and put the box end wrench on the center nub clocking it so you are pulling the cutter around as opposed to pushing it into the wall which will gouge it. You will have to change positions many times as you go around the cyl so you are always pulling the cutter blade which takes alot of discipline and when you get close to getting the ridge down to the wall CLOSELY monitor the next couple of turns as you dont want ALL of the ridge taken off as the cutting rate varies and you dont want to take ANY off of the wall so you need to stop JUST before that point because when the piston is at the top is when combustion is taking place and ring seal (& power produced) is the most critical and you dont want to make the taper worse. I'm assuming the eng is still in the vehicle? Myself I'd rering/bearing it (w moly rings) and read "breakin secrets" (a 5 minute read) at www.mototuneusa.com. EDIT had the address wrong