I would say no, that shit never happens. Need to take into consideration that shit like that can happen, and think of the risks of what you are buying. So its just part of the process, gonna have to bite the bullet every now and then.
One bad deal doesn't make him a bad seller, also how could he know how you installed a motor, or if you did make a mistake installing it, or if you f'd it up yourself and are trying to pin it on him.






