Plastic

Start the engine again and heat it up then use a ‘cotton’ rag to move/scrape as much as you can off it.

 

I'd sharpen a wood chisel and then carefully scrape it off while it's still cold.

 

Thsovik
You got the best two answers possible. And I sometime after scraping use an oven cleaner and finish with solvol autosol. Welcome to the family by the way. What bike year have you got.
Regards
Joe.

 

I had the same problem a while ago wen a plastic shopping bag blew on to the engine and exhaust. I did not notice until I got home. I let the engine cool down and most of the plastic just "snapped" odd in large lumps. For the few small pieces that were more difficult to remove and used kitchen cooking foil, scrunched into a small ball and dipped in tap water. The foil was abrasive enough to remove the plastic but did not scratch the chrome. There is a chemical in the foil which, when wet, reacts to the chrome and brings it up a treat. I don't use Autosol as it contains a aggregate which can scratch the chrome. Harley Davidson produce a "smooth" chrome polish which is far better, but to be honest I've never needed it after the kitchen foil. Good luck.

 

yep happened to me put the cover on to early just used steel wool and then polished the down pipe that taught me to wate until she had cooled down