I'm building a new single speed and the chain is not sitting on the cog correctly. I used a foundation single speed kit from jenson and the shimano 10 speed chain shown below.

I would probably use the correct chain designed for that system. It looks like a pretty low cost system so probably designed around 1/8" or 3/32" chain which are designed around single speeds where 10 speed is designed for 10 speed set ups. There are some nicer single speed cassette cogs that are designed around 11 speed chains but this is a good place to start to figure out what gear you want and if you like running single speed and then you can potentially upgrade down the road.

Looks like your choice of chain is too narrow between the inner plates.
A traditional single speed cog needs an 1/8” chain.
Multi-speed chains got narrower, in order to fit multiple cogs in a limited space (width).

Barry

In the Q&A for the product on Jenson, 3 users answered that they are using 1/8 inch chains. Though another similar question was answered by Jenson stating that both should be okay.

I'd go with the answers that were framed as having been from people that are actually using the product.

Was there no documentation included with the kit suggesting what chain to use? Jenson had no manufacturer links, nor could I find any on a simple google search.

If you figure this out, you should go to Jenson's site and add your findings to the appropriate Q&A's. Especially to the one Jenson may have answered incorrectly.

https://www.jensonusa.com/foundation...dxTe8ZdJDScHGc

The photo looks more like the chain is stretched out rather than too wide - otherwise it wouldn't fit right on any of the cogs, but it fits fine on the distal cogs and rides up on the top cogs.

Can you confirm that's a new chain? Can you measure it?
Does the chain "catch" on the teeth and then release while you're slowly turning the crank?
Does the chain float on top of the cogs and then snap in to place at the high tension spots?

mbe820 ,
Why not measure the thickness of the rear cog with a caliper and put this thickness mystery to bed.

Barry

New chain is unlikely to be worn or stretched as some call it. I can see why some might think that looking at the picture. I at first thought that the spacing on the cogs wasn't correct. Which also wouldn't really be likely for something others claim to be using successfully in the product reviews.

But looking at the picture closely, one can see that the chain isn't setting all the way down between the cogs. And the distance that adds is accumulative in relation to the further distance each roller sits from the center of the sprocket. And the end result where we see the chain roller sitting on top the cog that should be falling into the space ahead of that cog.

the teeth on the sprocket are too long, and the chain is too narrow for that same sprocket.

You need a 1/8" chain for that cog. Or you could get a 3/32" cog and use that chain. Also, if you were to use a 3/32" cog, for future reference, no need to use anything other than a decent quality 8 speed chain (SRAM PC-850 is my go-to for modern singlespeed setup).

bicycle chain width specs... ...

For inner chain width there are the following standard dimensions:

Single speed chains have inner width of 1/8″ (3.175 mm).
Multi speed chains, from 5 to 8 have inner width of 3/32″ (2.38 mm).
Multi speed chains from 9 to 12 speeds have inner width of 11/128″ (2.18 mm).
“Exotic” standard for freight bicycles is 5/32″ (4 mm).

Props to Bike Gremlin for this info!

actually, that 10s chain is narrower than the 6-7-8sp. 3/32" size...

It could be 3/32". Any inch measuring tape will do. Using a crescent wrench could help too.
Anyway, do NOT use 1/8" for 3/32". It will saw back and forth on the cogs and will mushroom the hollows.

Classic single speed and track chain is ⅛" wide, more modern may be 3/32" which is the same internal width as 6/7/8 speed chain. Your 10 speed chain is narrower. Best to measure the width of your sprocket with a vernier or digital caliper before buying another chain.

If your cog was intended for use with a 3/32" chain, I don't think it would matter that you're using a 10 speed chain, I think that would work. I think the problem is that your cog is for a 1/8" chain.

Here's a photo of a Surly 3/32" cog with an 11 speed Shimano chain wrapped around it. It would work fine, but I would use an 8 speed chain if this were actually on a bike, if for no other reason than the cost of the chain.

I put a sram single speed chain and is working fine. Thanks for the everyone