Hyper V Network Server

I have a server that has 4 Nics.  The operating system is Server 2008 R2.
This server is setup as a standalone Hyper V Server.
3 of the 4 Nics are associated to Virtual Networks, each Nic serving to a different network.

For example Nic 1 is not used by any virtual network and it is to this nic I am able to RDP into it and manage the server.
The ip address is 10.10.10.1 and it has a gateway that gives it internet access.

Nic 2 which is used by a virtual network has the ip 10.10.50.1
Nic 3 which is used by a virtual network has the ip 192.168.50.1
Nic 4 which is used by a virtual network has the ip 172.16.234.1

There are several virtuaul machines and workstations and they all respectively use Nic2, Nic 3 or Nic 4 depending upon the network they are connected to.

From the Server, Nic 2, 3 and 4 are all connected to switches that are part of that network.

The problem I am having is that if from the main server I am trying to access the internet but it says it cannot. On further investigation I note it is trying to go out via Nic 3 which has no internet access.

How can I get it so that the main hyper v server only uses Nic 1 ?