ORIGINAL: Dobe
Yes, the front bearing is wet, and oil leaks from it, I didnt really look too much into this because the same thing happened with my novarossi, its just strange because it was perfect last time and now all of a sudden its gone bad.
There is your answer, it's the same problem 421Bs havewhen you run them higher than Idle they have to be richer than normal, then you brake and it cuts because it suddenly leans out because of the air leak on the front bearing.
Do you use ARO?
I'll BET if you change the front bearing this problem will go away.