I'm on the condo board at my building and, as Corporate Secretary, am in charge of the Rules and other legal documents. I have two motorcycles and car (but two parking spots). There's another motorcycle owner on the board so no issue in my building. Some comments:
1. Usage of the parking spot is specified in the Declaration, not the Bylaw. To change the Declaration requires 90% approval from all owners. This is next to impossible to achieve. Bylaws require 50%+1, and even getting those passed is a challenge.
The exact wording of the relevant section of the Declaration (yours may vary but lawyers like using templates!) is as follows:
"Each Parking Unit shall be used and occupied only for the parking of a motor vehicle as may be from time to time defined in the Rules... the Owners of Parking Units shall not park more than one motor vehicle within the boundaries of such Parking Unit... in no instance shall any portion of any motor vehicle parked within a Parking Unit protrude beyond the boundaries of the Parking Unit and encroach upon any portion of the common elements or upon any other Unit."
2. In our building, we are obviously ignoring the first part of the wording (i.e. only one vehicle allowed per spot), but we enforce the second - i.e. you shall not exceed the space you've been allotted. We have high calibre people on the board (all professionals, not just a bunch of nitty busy-bodies) and take a pragmatic approach to these things. Your board may be full of frustrating nits. If they choose to enforce the exact wording of the Declaration, there will be little you can do about it.
3. If you have any evidence that there have been more than one vehicle parked in a spot for any length of time, you can use that as a defense. Provisions of the Rules or Declaration that have not been consistently enforced lose their effect (at least that's how judges have ruled, especially in cases related to pet restrictions).
4. Get on the Board - it's the easiest way to make changes and argue your case. Plus you may learn a few things about how condo corporations operate. I particularly like to keep an eye on management, the budget and potentially reckless spending.
Good luck!