Have you tried, gently, very gently, turning the key when you have it partially inserted?
Your lock cylinders might be out of alignment, and you might just need to gget them lined back up.
I'd use the stronger steel key for this, the worst thing you could do is snap the key and leave half of it stuck in the ignition.
You might also try moving the handlebars a bit as you attempt to insert the key. I know I have to jiggle the bars occasionally to get the key out.
"I've always been crazy, but it's kept me from going insane." Waylon Jennings