The only answer to a worn out, damaged or missing instrument, unless you possess the skills of a watchmaker and electronics engineer, is to renew the assembly.
These are virtually impossible to repair, unless you have the aforementioned specialist skills, and renewal with this superb quality OEM replacement is the only realistic option.
Check this out: 37100MZ2601.
Alternative and related meter components you may wish to consider:
Repairing instruments and their casings, cowlings and lenses is somewhat specialised, if you do not have that skill set, then replacement is easier.
Add as many parts as you wish to the same shopping cart, new anti-vibe rubber 37244MB2008 and new speedo cable 44830GC8000 for example, and still only pay the same single fixed price shipping cost.
If you want to discuss this LENS SMOKE, please go the forum and post a message.For questions about Honda St1100a Paneuropean 1999 (x) Austria / Abs 50t, please write a message in the forum.
St1100a Paneuropean 1999 (x) Austria / Abs 50t forum
posts from the Honda ST1100A PANEUROPEAN 1999 (X) AUSTRIA / ABS 50T forum