Regarding the tire/wheel combo- Are these not the famous Harbor FAIL wheels that everyone here knows better than to use? PLUS- Since those are all "freewheeling" wheels, you'd have to remove the bearings and source or fabricate hubs to work with them.
There is no way (around here, anyway) you're going to get sufficient steel stock for $15. You may well get lucky scavenging it, but you're not going to get it from a steel supplier at a retail level for that price.
Finding a usable engine for $25 is doable, but like everything else, can vary regionally. In some areas (again, like mine) you will be waiting a long, long time to get a $25 engine.
And, like the above post stated, you may have an engine, clutch, rolling stock, and some steel for your $100 budget- but you need much, much more- with no room left in your budget.
I'm not trying to be a jerk, here- I'm just trying to illustrate that building a kart for $100 may be possible, but will prove quite a challenge.
Timeline- You'd better not be in any hurry whatsoever- Awesome deals, freebies, and roadside finds don't tend to present themselves on schedule.
Tools- You'd better have everything you need! I once was forced to spend $15 on a specialty drill bit for a project, and have not used it since. Imagine how fast a few tools could crucify your $100 budget.
Ingenuity/Resourcefulness- You'd best have plenty! Let's suppose those above HF wheels are okay for the job. Let's also suppose that the bolt holes in them do NOT match the PCD of standard hubs- Now what? Having a machine shop make hubs for you is not only going to detonate your $100 budget in one shot, it's a dam foolish idea to do that for $10 wheels! Agreed?
I speak, because I have lived it. I built my kids' kart (The Green Machine) for just a shade over $200. I spent $20 on new upholstery and John Deere graphics, so let's subtract that because I chose to pretty it up and was not crucial to the build. I spent a little over $100 on a new 4hp Kohler Clone because I was treating myself. If I had set the budget, I would have re-used my old Tec H60- so for argument's sake, let's delete that cost, too. That puts us at a little over $80. Let's call it $100 in case I am forgetting something.
I was very fortunate to find all the scrap steel in various locations, equally fortunate to come across that old lawn tractor that donated so many parts. An industrial ventilation fan! Let's be honest here- not many folks would throw one of those in the back of their truck to build a go kart! How about the ATV rod ends in good shape that I quite literally found in a field one day? Can you factor that into a budget? And many, many more parts I have not mentioned. Now- Here's the really hard part-
The task itself was gruelling. Having the patience to wait for useable stuff to come along free or dead cheap nearly drove me insane. And what DID drive me insane was working out how to make a hundred unrelated parts all work together smoothly and reliably. Harder than one might think.
Realistically, for the $100 budget, you cannot "count" having an uncle who owns a scrapyard, a once in a lifetime deal, a brother who welds, etc. Why, because the intent of this thread suggests that anyone can build a kart for $100. Not everyone has a grandfather with a machine shop.
Can it be done? Yes. Easily (and decently)? No. Can "anyone". No- I don't think so.
There's my two cents. Actually, that was about $10 worth, so you're down to $90 in your budget!
Its the parts that kill your budget.
