What he has:
New: An Acer CB3-111 Chromebook was around $180 new a couple of years ago. Used: They look like they can be had for $115 on ebay now.
What you have: (estimated after a quick search)
New: A 49cc kit on ebay is $97
http://www.ebay.com/itm/2Stroke-49c...ash=item58e633782c:g:jqQAAOSw-0xYO6kY&vxp=mtr
New: A 80cc kit on ebay is $100
http://www.ebay.com/itm/80cc-Bike-B...ash=item2ef72a55a4:g:nZQAAOSwtnpXooY4&vxp=mtr
New: A Kent fixie at Walmart is $99
https://www.walmart.com/ip/700c-Kent-Thruster-Men-s-Fixie-Bike-Yellow-Blue/40519014
So, new value for the bike parts is about $120 more than the new value of the laptop.
However, the $99 bike will have very little value with the holes in the frame unless you find someone who could use some of the parts. I think you are looking at rummage sale price on the bike after looking at the chainstays. As far as the motors and stuff, If I saw a lot of two motors, one used and in a box, I would assume the one in the box is not working and would make an offer accordingly.
I would offer you the price of what two used long blocks would be, but this guy might be able to get some use out of the parts so the lot might be worth more in value to someone who could use some of the parts.
I think he would be getting the better part of the deal but your asking price of $400 is out of line, considering you can buy everything you are listing brand spanking new for under $300. (unless there is some cool stuff in the box I'm not seeing)
He is getting a better deal but I wouldn't consider it a low ball, maybe ask if he can throw something else in that you want to sweeten the deal.
and dude.... you are 17 and posted your pictures, govt ID card, name, phone number etc. on a public forum. c'mon maaaaan go back and delete that s#!t.