Hi,
I had a similar problem, but my cvh 4/4 has a dft weber carb.The choke sometimes would work and sometimes not, but the tickover was always slow.
When i dismantled the auto choke mechanism i found the plastic part of the mechanism that raises the tickover speed-had snapped off, and was rattling around inside the cylindrical casting.
Gomog had the weber manual and part numbers.
I bought a new auto choke mech off E bay.
Hope this helps someone...