[redtrummy]

You need to keep the mice out of your bike full stop. An acquaintance had all sorts of strange things happening to her motorhome. Using the indicators would bring the headlights on e.t.c . Turned out (eventually) the blighters had nested under the dash and had a field day munching the wiring harness.
I dont like killing any thing (apart from slugs) but next autumn you could try an electronic repellent or something they are reputed not to like the smell of, e.g chili powder or ammonia and back that up with a few mouse traps if need be. Assuming that is they are field mice