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piston seized after doing top-end.........
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[QUOTE="spanky250, post: 153344, member: 20897"] The answer to this is no. The heat cycles release the frozen stresses in the metal that are left over from the manufacturing process. We performed an experiment in Tech school on this subject. We took two pistons, one brand new, and one used, and put both of them in a 500 degree oven for twenty minutes. The used piston came through this test unscathed, but the new piston was distorted beyond recognition. The heating cycles during break-in help to relieve the stresses, while the cylinder keeps the piston from distorting. Since the piston is trying to change shapes during this process, rushing the break-in and trying to push the piston too hard too soon will allow it to distort enough in the cylinder to seize. I also believe that the heat produced by the combustion is not the only factor at work, you also have the huge forces placed on the piston by the acceleration and decceleration that occurs at the end of each stroke, and by the extreme pressure rise that occurs at the moment of combustion. I am no engineer, but I have always carefully broken in my pistons, and have never had a new piston fail during break-in, nor have I ever cold-seized an engine, because I carefully warm my engine before riding. I have many friends that ride, and most of them are less careful about these things, and all of them have had piston failures and seizures over the years. Even the bike that I currently ride had been cold-seized by the former owner, requiring a new top and bottom-end rebuild. [/QUOTE]
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Dirt Bike Mods & Maintenance
piston seized after doing top-end.........
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