400ex valves and sprins

[sc400ex_rider]

hi im going hc stg 2, 450r carb, 11.1 std bore, should i upgrade? are the stock valves good? thx

[zrpilot]

If the stock valves and springs are in good shape, you would be OK, but if I were you, I'd at least put new stock springs, and valve seals in during the rebuild.

Better yet, just send the head to a reputable engine builder (like Colby at C&D) and let them tell you what should be replaced.

[vett_09]

That's what I did when I rebuilt mine, new springs and seals. It's easier to do it when it's all apart.