WD40 attacks the zinc in chrome and turns it an ugly black just before it blisters and peels off!
JUST KIDDING OF COURSE
You should have no problems with anything by spraying it where you did. If concerned give your bike, especially the engine, a good wash down before you fire it up in case WD40 does cause discoloring from heat. (electric leaf blowers are great for drying)!
I use it all the time, but never on my firearms for fear of discoloring.