Bike mean not bicycle (that's means motor bike).
Otherwise If i were talking about bicycle, then there would be a mention. However, I have mentioned motor bike here and it's one of my favorites. But of course it is not good for our body even bicycle is very convenient for our body.
Oops.
Most of us thought that you were referring to bicycles or cycling. Yes, you should have mentioned that you're talking about bike motor or motorbike instead of saying a bike.
Anyone will easily think that it's bicycle you're referring to.