You'll need to grind off the link at the distal end of the 166th link. Then, using a punch, punch out the pin that connects the links. Or get a chain cutting tool(I've never used one) they sell them in motorcycle shops.
There are a couple ways to do this.i got a new RK Chain for my bike(Rx-Ring Chain) all they had it in was the 120 link and I according the the vortex catalog I need it in a 116, so how do I remove links?