Weller PU-2D Soldering Station

[Bushbaby]

Help!
I've put a new bit on this solder station - a No9 degree bit (the hottest). It always seems blued and I'm concerned that its running too hot as when I tin cable ends its melting the cable even though I'm doing this as quickly as I can.

Should I revert back to the No7 degree bit that I have?

Thanks

Rob