Just built up a single speed as follows:

Phil Wood 113 bb
White Industries ENO chainset (32)
Hope trials hub
Chris King cog (18)
KMC 8 speed chain

All seems to spin freely and smoothly, but there is a constant noise almost like the sound of a skipping chain with a badly adjusted rear mech.

Possible causes:

Chainline – it looks OK to the eye, but how do I tell exactly?
Chain tension – what’s the ideal?
Chain – I thought that an 8 speed chain would work fine with the chainring and cog combination. Is this not the case?
BB – stripped and refitted, and brand new, so probably not the culprit and it definitely sounds like a chain noise.
Freehub – perhaps, but how would I tell.
Bedding/Mashing in – is it just a case of the chain cog and chainring needing time to get to know each other (all parts are brand new)? In your experience, might it just pass?

Any help very much appreciated. Only ever had 1 single speed in the past, and it was silent.

What would you suggest?

Thanks!

Sounds like the chain too tight.

Chainline – look along the top of the chain from the chainwheel end. If it looks to be leaving the chainring straight its good.
Chain tension – should be about an inch of up and down movement, but chec this on all rotations of the chainwheel as they aren’t always round.
Chain – 8 speed chain should work – with the wheelout check the inner plates aren’t tight on the chainring

Whip the chain off and hold a straight edge against the chainring. You should be able to see how straight the chainline is. I aim for +/- 1mm.
The chain should be tensioned so it just has a bit of slop- not twang-if you know what I mean.
Are the Chainring, cog, and chain all new, or all old?They need similar amounts of wear to avoid skipping. Edit: As you say,they’re new.
THe freehub could be at fault, with worn pawls or whatever.Investigation bt someone who knows Hope hubs is needed.

Check for tight links in the chain.

There’s nothing worse than a noisy singlespeed!

+/- 1mm is anal 😉 +/- 10mm is fine 🙂 Good call about tight links in the chain.

Are the rings/cog definitely 3/32?

Straighter the chainline, the quieter it will become. Rather 1mm than 10 MM !!. Check with a straight rule and se what you have first and go from there. If you use a specific single speed chain, it will not flex sideways and catch the sides of the teeth on sprockets and chainrings if set up fine, but will still work with what you have.

Thinking about it, is anything worn? I had a King sprocket on mine which sounded like a cement mixer with a new chain. New one fixed it. Just a thought.

Another thought; Are there enough spacers on the freehub to hold the cog tight?

Does it happen only when pedalling or all the time? Do you have a speed link in the chain and if so, is it the right one, I.e 8 speed? I once had a 9 speed link joining a 10 speed chain and was making a similar noise to what you describe. Took me ages to find it and was driving me nuts!

I vote 3/32 or whatever an 8 speed chain is, running on a 1/8 cog/chainring.

Thanks all. Really helpful.

It was the chain line. Tried the tension first, but no luck. Even tried the chain super slack, but it was still noisy.

The front chain line was 47.5mm. The rear was at 65.0mm even though it looked fine by eye. Fortunately the Hope trials hub has plenty of spacers to get things just so.

Now running smoothly and silently. Will post some piccies later. Loving the simplicity of 1 gear, but so far still reaching for a ghost shifter with my right thumb at times!

In answer to some of the posts, the chain does have a quick link, which is now running silently. Not sure what the optimum chain pitch is for the White Industries front and Chris King rear, or if they even need the same pitch, but they both now seem quite happy with the 8 speed KMC chain.