Mine (o5 Speedmaster) is the same way in the cold. Ten minutes to get her up and at 'em without burping isn't unusual for mine. I chalk it up to no heat riser on the carbs, and no benefit of electronic controlled choking that some EFI brains may allow.
After a very loooong month of motorcycle deprivation, I'm out for a cold weather ride today & tomorrow. It's 32 F here now, and up to a balmy 40 later. A pounding rain yesterday washed the road salts into the ditch.
Yee-hah!
