Hi wce
I think there is a little grub screw retainer in the fuel tap - i see the hole in the photo, but it may just be recessed.
The carby is very heavy - and i too was scared when i pulled the first one i had apart.
With regards to starting, from memory its fuel on, throttle at 1/2, choke lever (under fuel tap) up, hold the brass button down until fuel comes out of the hole next to it. then wind handle 3 times, then trip the switch.
When it starts leave it like that for 5 seconds, then off choke and throttle lever back to idle to warm up for a minute.
By the way, if you take the carby apart again, don't try to remove the needle without removing the brass vertical where the jet is (done so by 2 crews on the outside).
