It melted on?
So try to heat it:
Start the engine, and when it gets warm try to scrape gently with a wooden stick.
I have not done this, but I would try if it was my bike.
Liv's right!
There I've said it. A woman who is right about something. Must be because she rides a GS... Maybe if all women rode GSs then life would be a lot easier.
Last year mates of mine from Ireland came to the WSB round in Brands while staying with me one picked up some plastic (from the Halting Site;-)))
We ran the engine for a while and use a stick to scrape off the offending plakky. Then wearing a stout Rigger glove rubbed the pipe clean OOH ERR with some wire wool.
Job done.
Pat the Pikey