230sl rhd 1965 backfires

[James]

Hi all
I’ve just had my car serviced… new plugs and points too
Drove it down to the coast for Summer and it  backfires and is a big smoky from the exhaust for 10 minutes or so on startup.. which it never did!.It ran ok on the freeway.
It’s too inconvenient  to take it back to the mechanic
I think it’s just that the fuel mixture is wrong but I’m not an expert
She’s otherwise perfect.
Any easy suggestions?
James