http://mgaguru.com/mgtech/carbs/cb116a.htm
http://mgaguru.com/mgtech/carbs/cb116b.htm
I didn't read the links, but I'd start by trying flatten out the fork on the left.
If all else fails, I can perhaps send you a substitute float cover. I'll have to dig around to see what I can find, but I have some partial H4 carbs in the basement.