Valve face recutting VS grinding/lapping

[Nessism]

Isn't that also referred to as a 3-angle valve job? In other words, two separate angles are ground on the valve face and then a third, different angle is ground in to the valve seat.

A three angle valve job refers to angles on the valve seat. Suzuki uses two angles on the valve seats 15 degrees and 45. Valves are typically cut at only one angle - 45 degrees. Back cutting the valves results in two angles on the valve; the standard 45 degree cut (part that contacts the valve seat) and a second cut to aid gas flow at low valve lift.



Examples of a three angle valve job on a Honda auto engine...

[headsbikesmopars]

Flago60/notabiker, Back cutting does nothing to the valve seat itself. It is a cut that is above the seat (45) on the valve itself. It removes the 'corner' at the very top of the 45 cut on the valve face. Has noting to do whatsoever with the valve angle on the head or valve. The 45 is not effected at all. If you lap your vales in you will see that the face of the valve is longer than the 45 seat itself, (on the valve). There is margin left. Back cutting up to the edge of the 45 with a smaller angle takes off that part of the valve, knocks the 'corner' off so to speak. Opening up more clearance (valve area) and exposes more of the port for air flow. The valve job isn't effected at all. This is part of the valve that doesn't touch anything. This dosn't affect the longevity or reliability at all. Nothing but a positve gain here. A win-win deal. Check out the fine photo's Nessism posted. Just trying to help out a fellow GSer. Easy and cheap, My flow bench likes it too.