Serdi Valve Seat Cutting
Replacing your valves is a very important part of your engine maintenance. Valves are under a lot of stress and care must be taken when replacing them. More often than not, most repair shops will just install new valves without cutting the worn valve seats or replacing the worn valve guides.
Some shops that offer valve seat cutting are using hand cutters. The valve seat has different angles usually 30, 45 or 60 degrees. To do this cutting with hand cutters requires each angle (i.e. 30, 45 or 60 degrees) on the valve seat to be cut separately. These hand valve seat cutters do not have the accuracy needed. If the valve seat is worn out of true, the hand cutters can only follow the same contour. The hand pressure of the technician can vary. Trying to transition the different degree cuts needed to cut the valve seat cannot compare to the quality you get with specialist machining equipment. The exactness cannot always be seen by the eye, you need special measuring equipment. Most shops that use these hand cutters do not use a concentricity gauge to check the valve seat surface concentricity. This gauge is essential to make sure the valve seat is perfectly round or within two thousands of an inch (.002″) for reliable performance. A race engine should be less than one thousand of an inch (.001″). To put this into perspective, the average human hair is 3 thousands of an inch (.003″). If the valve seats are not cut at all or they are cut with hand cutters, the engine will most likely run, but due to improper valve seat contact, the valves will wear out prematurely and you will not be getting the maximum performance.
The best and most accurate way to cut valve seats is with a machine like a SERDI valve seat cutting machine. This is the machine that most professional Supercross, Motocross, F1, motoGP, and NASCAR teams use. The SERDI is a very expensive piece of machining equipment but this is required to accurately cut the valve seats. The SERDI can cut all the angles (i.e. 30, 45 and 60 degrees) of a valve seat at the same time with one pass using a carbide cutter. What makes the SERDI so accurate is its ability to float on air to find the true center in the valve seat to perfectly align the pilot before the cutting begins. This is the only process to ensure an accurate valve seat match. The last and most important step is to check the precision work with a concentricity gauge. Quality precise machining, confirmed with the use of a concentricity gauge or vacuum test, is the only way to ensure the best performance and reliability of your valves.