If you get any tar on the bike whether it be plastics or exhaust, there is a product that can be really recommended. I also use it on the car when tar has kicked up tar up the sills and lower parts of the door so its safe to use without damaging paintwork.
Mr Sheen Multi Surface Polish Original.
Good for plastic, glass, metal, plastics.
Just spray on a blob of the polish onto the tar. Leave about a minute or 2. Tar will just wipe away. You can use this polish for a quick wipe round the bike.
Paul