2. Troutman also touched up the intake and exhaust valve seats to make sure the cylinders were still sealing optimally. One of the keys to making power with an LMS engine is maximizing the compression ratio. With the required flat-top pistons, that comes down to making sure the combustion chambers are sized right at the 62cc minimum. Both decking the heads and cutting valve seats (which raises the valves into the chambers) can affect combustion chamber volume, so Troutman checks cylinder head volume several times during the process of his machine work to make sure they are still very close to that 62cc line without going into illegal territory.