Originally Posted by Bryc3
Right now I have a 7.0HP lawn mower and a smaller weed whacker. I'm definitely a larger guy (~220lbs) and I was thinking that I should go for the lawn mower engine. Does anyone have any objections or any tips?
My main concern is that the lawn mower is overpowered and the weed whacker is underpowered.
A seven horsepower gas engine is not overpowered in any meaningful sense of the word. But it could be excessive in all the other things that go along with it-- size, noise, vibration, weight distribution, etc. It also might move the speed of your bike into a range where either you or the bike do not operate safely.
It seems to me like a better engineering exercise to make effective use of the limited power of the smaller motor. If you have the motor drive through the bike's gears, you can do a lot with a small amount of power-- which is what bikes are for, anyway. You could end up with a bike that's road-legal in your area, and more fun to ride too, because of its light weight and small displacement.
You'd need to carefully match the motor's output speed to the bike's drive chain speed for a range of real world conditions, which is a more complex and satisfying problem to solve than just changing the orientation of the output shaft.