Are you using a bicycle/ motorcycle chassis, or making it from scratch? Well if you make this and it works, you should not do this: Good luck! Please put pictures of your progress up. Or videos.
any welding experience? Any experience bolting engines up? If answer to either of those is no, you're about to kill yourself mate, take a step back, get some practise in, revisit it later. If you are going ahead, I can tell you what not to do: http://hackaday.com/2016/07/12/fail-of-the-week-how-not-to-build-your-own-motorcycle/
Honestly it would probably just be cheaper to buy one already built, and it would definitely be a lot easier.