engine of bike

I think you could but... what the number of cylinders of an internal combustion engine (I am assuming you are talking about it reading your post) have to do with its power output, weight, size, speed or torque, or consumption? There are a number of multi-cylinder airplane models engines that weight around 500 g, and there are huge one-cylinder engines for bikes, for example. Please, direct your attention to what is worth. As a suggestion, what about using a hybrid configuration with a really small engine working attached to a generator that charges a battery continuously (or turning off when not needed) and an energy recovery system to drive the wheel?