Chain slipping

[broady]

Just converted a road bike to a single speed and I am getting some chain slipping. It's a new chain, new rear cog, used chain tensioner and am using a 9 speed 42 tooth (I think) crank.
Chain line looks fine and no issue when you just turn the pedals until you apply extra force.

 

[e-rider]

what width chain is the rear cog made for? 1/8", 3/32"....................

 

[broady]

Good question that!! I'm not too sure as I got it second hand.
I do have a few chains around so maybe I'll see what other bits I have laying around

 

[broady]

Changed the rear sprocket to a 17 tooth off a 9 speed cassette and working fine.
What is a 9 speed chain? 3/32"? And what would that make the original cog?