The back story.
I had to go to the scrap yard today. We were cleaning out the shop and I had a pile of aluminum and steel to get rid of. When my son and I pulled in the yard, I noticed a couple of mini-bikes in the steel pile.
Being the inquisitive kind of guy, I asked if they were sale. The answer was no, they weren't allowed to sell anything. I let that ride for a bit and we continued to unload my pile.
Toward the end I offered a trade. Some worthless green paper for a couple of mini-bikes. Still no.
As we were cashing out, the manager offed to weigh the bikes and trade that out for equal weight of steel. I ended up paying 3.5 cents a pound for them. 
The plan.
We will be getting them running. I've got an assortment of engines and parts we can dig through to get them back running. Should be a fun build, but probably a very slow build. The plan is to get the grandkids involved as well as their uncles. The grands are only 5 and 8. 
Yeah, I'm curious to see how these turn out. I see some knock off branded ones pop up <$100 from time to time that won't start/sitting out a while/etc and wondering if it's be worth it to kick around on.
In reply to johndej:
I'm kind of curious myself.
Nice! My son just went and bought a Coleman fat tire mini bike which looks abit like the bigger one you have. He paid 150 for it, and has been researching how to build up the engine, CVT clutches, etc.
I had something like that back in college! 1969 Rupp Rascal with a 6 hp tecumseh flathead that made a lot more than 6 hp. The thing would wheelie uncontrollably when the centrifugal clutch finally hooked up around 20 mph, and of course there were no brakes aside from the scrub brake, which was a little metal plate that rubbed on the rear tire. Low CG made for excellent 2 wheel drifting in the snow, too.
I once caught the seat on fire while riding it when I floated the valves (flathead) and the exhaust turned into a flamethrower. Good times, good times.
oldminibikes.com used to be my go-to resource, and some of the info may apply to the newer ones.
A good thing about small projects is the ability to work on them in the shop...with the A/C set to sub-arctic.
Thar be parts on the way, matey. At least for the fat tire machine.
Broken or missing, was the clutch, throttle handle, brake lever, and starter assembly. It's all on the way. I'm skipping the clutch and jack-shaft, and installing a CVT instead. That should give better low speed for the kids without slipping the clutch. It should make it more capable for tight trails through the woods.
More to come.
The old Minibike forum is a great resource for these, and there's nothing you can't get for those Honda clone motors. I have one like your fat tire bike, 12-1 compression, high lift rockers, 226/236 cam, and a pile of other stuff, and not much more than a few hundred into it. They're loads of fun.
Be careful,
dad paid $500 for a running z50 (circa 1974).
He now has over $2k in it for all the parts etc...
I myself bought a lifan z50 clone a few months ago. I tried to start it once and the regulator started smoldering, which is placed under the gas tank. I then in a panic ripped the body panel off to get to the battery to disconnect it... I have yet to touch it since. Need to see if it needs a new motor or if I can rebuild it. Putting the two side by side it's pretty amazing how similar they are. My biggest gripe on the lifan is the fact that the seat is not adjustable on it. Vs the z50 which at it's highest setting is somewhat usable as a 6+ ft adult...(though pretty funny!)
It got too hot to work on SanFord, so I moved into the A/C, to work on the mini-bikes.
Good news and bad news.
I got a box of parts in for the Mini Baja. The throttle, brake lever, and starter showed up. I figured I would get them installed, and see if the thing would run.
Starter:
Throttle and brakes:
The good news is the throttle and brake lever fit perfectly. The starter didn't. The starter is for a Honda clone engine, and the engine on the bike is actually a Honda. I had to do a little modifying for it to work.
I had spun the engine over by hand several times and it felt pretty good compression wise. The fuel smelled mostly like gas. I pulled the oil plug to check it, and it looked particularly bad. When a engine is coming apart, the oil gets a particularly nasty black color to it and that is what I was seeing. I went ahead and topped it off hoping for the best. I turned on the fuel, set the choke, and pulled it through a half a dozen times. From there, the compression disappeared. I pulled the valve cover to see if there was a stuck valve. I think the cylinder is worn out. The compression I originally felt, must have been from oil around the piston, from the bike laying on its side.
I can pick up a 6.5 hp HF clone engine for $100 so I'll stop by there tomorrow on the way home.
While I was working on the bigger bike, my youngest son was working on the small one. The engine on it was also past the point of repair. It's one of those irritating 2 strokes, so I'm not going to spend any time trying to fix it. I had a 3 hp HF clone engine on the shelf that we will be using on it. He got the engine pulled, the rear axle reinstalled correctly, and started sorting out the mass of wires from the lights and turn signals. No pictures of that for some reason.
More to come.
Spent a couple of hours in the shop this afternoon. New rear tire mounted. New engine mounted.
And just as I was locking up the shop, this showed up. The dual chains and centrifugal clutch are being replaced with a CVT.
Is the valve cover on the 212 cast aluminum? Those ones are the hemi heads.... Lots of mods to be done there... 18lb valve springs keep valve float down once the governor is removed, and are cheap too.
CVT mounted, working on the chain alignment. The CVT is in the way of the sprockets lining up. I might have to modify the frame or the CVT. I'm going to sleep on it and see if I come up with any brilliant ideas.
The youngest has the little frame stripped down. We are going to have to move the sprocket to the right side, rather than the left. That's going to require some welding of brackets for brakes and chain guards. We are also going to have to heavily modify the engine mounting plate for the new engine.
