Any ideas what this noise is?

[guile]

A recurring 'blop' sound that is linked to the speed of the bike. It happens even when coasting. Imagine you put some glue on a small part of the tyre, that is what it sounds like to me with the glue slurping against the road.

Had rear tyre changed since it started (obv the chain was adjusted too). Asked the mechanic to look over the front tyre but neither he nor I can see anything.

Warped disc? No reason why that could have happened.

Any ideas?

[Pete.]

Usual suspects are tight spot in the chain, cracked/warped disk or loose bearing spacer. If it's once per revolution it's not the chain but it's hard to decide that if you're on the bike.

Put it up on stands and turn the wheels slowly. If it's some form of drag on the brakes it'll stop the wheel from a slow coast.
____________________
a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[guile]

Would a loose bearing spacer be making the wheel run out of alignment and therefore rubbing on the brakes at some point?

Applying the brakes when coasting makes no difference to the sound apart from slowing it down, so I don't believe it is the brake discs.

As for chain, I did tighten it up some time back and still got an MOT advisory for it being too loose but I think it is slightly tighter than manual spec. There is still slack in the chain so I don't know how it could be causing noise.

Can't tell whether it fits with one wheel revolution or one chain revolution. It's actually more of a 'swish-swosh' sound.

[The Artist]

If it happens at low speed, get someone to walk next to the bike and see if it is once per wheel revolution to help narrow it down.

[Pete.]