Check the "cold start" lever that increases the fuel output by about double. It is behind the metering unit and operated by the "choke" cable. If not being pulled enough, it might give cold start problems; if it does not return to the "off" position when you push the choke in, it will run way too rich.
As James says, expect the plugs to look a bit black, they usually run rich at tickover. If you look at them straight after a good blast with no ticking over afterwards, they usually look better.