If it’s a Y-8, here’s what I estimated.
According to JAWA, the nose wheel tyre diameter is 900mm, so I used this to scale (I hope) line drawing to estimate the nose cone.
The nose cone is ~ of size (1.6*900mm) = 1440mm.
Then, given that, I estimated the diameter of the KLJ-3 radar, which is quite large, about 1020mm! So, probably closer to 980mm still.