"I used to have a bike..."

[Scotty]

That really made me laugh!
You're quite right.
"I'd kill myself " sounds a lot more macho than "I'm scared that I might get knocked off and hurt myself "
I might use the cooking excuse thought...

Often heard, sadly from eejits who think that it makes them sound like a crazed speed demon whom we should all admire, but it's a euphemism for "I'd be a crap rider with no idea what to do and a desperate need to impress others and likely make a total tit of myself"