BMW R27 carb problems

I have a 1961 R27 I just bought receintly.

It starts very hard when cold, usually I have to push it but after it warms up a little, as little as around one block, it starts good.

But when I am riding it and stop it increases in speed when it is idling. It runs down the road great.

I have had the Bing Carb apart two times. Everything looks good the slide spring seems good and the slide works good. I checked the throttle at the grip and it seems to be working good also. The last time I had it apart it put gas in the float bowl to see of the float would float and it seemed to do that also. I don't know these real good but I am learning. Thanks for any help.

Air Leak

It seems possible to me that you have an air leak between the carb and the head. it is not uncommon for folks to overtighten the 2 nuts holding the carb on and bend the "ears" of the carb. This leak causes very hard starting. To fix it you can either _
1 take the carb off and use a glassplate and grinding compound to make the mating surface flat again.
2 take the carb off and put some soft gasket cement on the gasket/heat blocker on the studs - then put the carb back on.
Hopefully this helps.

more info in profil.