got this from BlackdiamondValves for CB750s from 69-76
BLACK DIAMOND® Valves • Black Nitroneg Stems
KPMI NO. Type Head Dia Stem Dia. Tulip OL Remarks
30-4186 IN 32.00mm / 1.260” 0.2590” 23º 4.040” Standard
30-4187 IN 33.50mm / 1.319” 0.2590” 23º 4.055” Oversize
30-4188 EX 28.00mm / 1.102” 0.2580” 29º 4.040” Standard
30-4189 EX 28.50mm / 1.122” 0.2580” 29º 4.055” Oversize
nippon