Triban headset reassembly Does anyone know the correct order to reassemble a Triban headset (specifically a Triban RC120)?
I bought the bike recently, was raising the handlebar height, but neglected to pay sufficient attention to the order in which the parts are reassembled. Two of the parts stubbornly resist going back (a large thin rubber washer and a wide plastic split ring).
A Triban headset exploded diagram would solve this problem. I've searched online but have come up with nothing. I've emailed Decathlon but they say they do not have have a diagram.
Reassembling a headset without documentation or notes is truly frustrating.
The plastic split ring is likely a compression ring which is jammed between the steering tube the top bearing,  if it looks like this:


Otherwise, it is a seal.
The compression ring does not have to go in easily by hand and is usually driven into its final position when tightening the complete assembly with a star nut bolt.
The rubber washer is likely to be a seal, but where it comes from is impossible to say. First of all, you need to determine if it came from then lower or upper half of the headset. Then you can try to find a position where it makes most sense (i.e. where it can prevent mud from entering the headset).
Good luck!