It’s cold outside. Carburetor choke on stock engines.

[geezer#99]

Good info!
Crankcase dilution is better known as fuel wash. Caused by a rich mixture getting past the rings. One of the reasons to not let your motor idle too long with a rich choke setting.
Fuel wash contributes to the early demise of many carbed motors. THe fuel washes the oil off the oil rings and cylinder promoting piston and bore wear.
Fuel injection reduced that immensely. The old carbed motors where good for 100,000 miles before rebuild and now the fi motors are good for up to 350,000 miles.
Good to see it's working better for him!