I serviced my headset today inspecting bearings and greasing the races etc. Upon reassembly I heard a snapping sound when retightening the steerer bolt and then found the headset impossible to adjust. No play in headset and the bearings are too tight, free movement and the headset knocks.
It's a cotic soul with cane creek 40 headset. I have inspected the assembly and all the pieces have been put back in correct order.
Star nut would be favourite for breaking up
Would the starnut be culpable for the lack of adjustment?
Late night crew?
If the threaded insert in the star nut has detached itself then that could be the problem. You'll be spinning the bolt but not actually tightening it.
Have a look at the crown race and cups, are they aligned with the frame and fork, no gaps?
Do the same where the bearings seat inside the cups, are the seats aligned and smooth all round?
Do the bearings move freely?
Is the steerer still firmly attached to the fork crown and aligned?
Take it apart and see what snapped, generally snapping noises accompany something snapping 🙂
Bearing cage
SFN has let go, or possibly preload bolt (screws into SFN) has snapped?
I had a star nut that somehow broke away from the steerer tube once, which obviously wouldn't allow the headset to be adjusted. However, if I'm reading your post right you're getting a completely loose headset which is locking up immediately when you apply preload (with no adjustment in between); I'd have thought that a loose starnut wouldn't allow any preload to be applied.
I've only had this happen to me once and that was with a new frame. It looked like the steerer was catching the edge of the lower headset cup (the bit inside the steerer tube) as soon as I applied preload.
My LBS faced the headtube and re-pressed the head set and everything was fine. I'm not sure whether I'd mis-pressed the cups (although a proper press had been used) or if there was a defect in the faces of the headtube (meaning that the cups were mis-aligned) but the problem did seem to be caused mis-aligned cups pulling the fork steerer in and up at an angle.
Have you had a look to see if the 'crack' was one of the cups moving or breaking away so that they're no longer aligned correctly?
I've been shying away from reading responses in shame. Headset was not assembled properly and the winning answer goes to rocketman. Bottom bearing had popped open under torque as it was assembled upside down in cup. I put it the right way and it popped right back into place.
Never perform maintenance and try and care for a 16mnth old child at the same time (glad her mum never reads this). 😳