What is wrong with the guy? What is wrong with the gal? Same answer: Lack of communication. The guy has a problem with his motorcycle, he has not communicated with his GF, so she begins to imagine the worst: He's got another GF and they're about to break up! He has no idea she's thinking this, and has no intention of breaking up-- nor does he have another GF-- but since neither one is communicating with the other, how can either know?
Alright, I'm going to spell it out-- again, because I'm aware that it's been said before: Men are not mind-readers. We can't know what's going down unless you tell us.
Women aren't very good at mind-reading either, even though many of them think they're closet psychics. You think you know what your man is thinking, and you guess wrong. Worse, I've had it happen so often it's not funny-- you guess he's thinking the absolute worst. So, what's wrong with the guy? He didn't say "Honey, the problem is my motorcycle won't start and I don't know why". I think that might have helped-- then again, maybe not.