What size kicker to go broke with in HU play

[Lovell77]

Lets say it's the first hand, so no reads and blinds are small. You raise on button with Kx, opponent calls and flop comes K 4 6. Opponent bets into you, you raise and opponent moves all in. I would generally call this with K8+. Just wondered if you think this is a bit too loose/tight, and what do you generally call with KT+, K2+?

The example's a bit vague, (bet sizes, board texture etc), just trying to get a rough idea. Also if you substitute the K for an ace do you find it makes a difference. I'm starting to think A-rag is way too overated HU (call a raise with any ace etc). In the early stages I wouldn't call a raise with K2, Q3, etc, although I always call with A2, A3, etc, does anyone actually fold A-rag to a raise.