Too small to ride a bike? You need 4 wheels and an engine then.

I had a nice long, 4-day holiday weekend to get caught up on my projects, so I started by taking some scrap to the metal yard.

And then I came back with this...

Son of a disc...

4 flat tires, smashed tank, bent handle bars and a locked up motor. I just had to have it. 

Frame, suspension, brakes all work and it's the perfect size for kids age 3 -8, so I couldn't just leave it there. I am the mechanical equivalent of a crazy cat lady...

Step one was to pull the dry rotted tires and popped inner-tubes out of there. This went easily enough, once I realized, the wheels are split-rims and no amount of prying would ever get a tire over the lip of one. 

Step 2: that bent handle bar. Well, the handle bars are fine. It's the steering shaft that's berked. 

Found some tube the right size, chromed to boot.

I straightened the ends on the lathe and cut the steering shaft as straight as I could... seems alright. 

I also used the level to try and get the ends as parallel as possible. 

Went back together just fine. Or at least way easier than the old motor came out. You had to disassemble to whole thing to get it out from between the frame rails. 

Also, I want to have a word with whoever "repaired" the electrical system...

4 wires, all side by side, with identical plugs and half the colors don't match. 

Well, I don't think any of the wires or the motor will ever see use again anyway. 

Next up, new motivation installation. 

I'm liking this project! who throws away a 4 wheeler?

have you got a young test pilot waiting to ride it?

In reply to Chappers :

I got a honda rincon 650 off craiglist in the free section because the motor popped. 

In Reply to Professor_Brap:

Now that's a find, even broken ones usually go for 200-500

In reply to Chappers :

I've got 2 very eager test pilots, one 3 year old and one 5 year old.

I had a 42cc chainsaw laying around that was dull and a little underpowered. I had already gotten frustrated with it and upgraded so I fired it up to make sure it still ran and started tearing it apart. 

I looks to be about half the size of the motor I removed but, my youngest is 3 so, probably a good place to start. 

First order of business was to figure out how to attach the throttle cable. 

First, I made a small plate out of stainless and shaped it to fit onto the end of the carb. 

Next, I drilled a hole and did some testing. 

Works a bit but it binds up since it can't pivot. So I found the stiff wire that was installed and cut it up and bent it into a circle that the cable would fit into. 

After a lot of fiddling, I was able to get it on there and functioning. You can see where I mounted the primer pump as well. 

The next big challenge is mounting the starter. This was a not too old, Homelite saw. Which means, that the whole body of the the thing was plastic. 

So when I removed (butchered) all of the plastic, I left no place to reinstall the pull starter...

It's been a while and my (now 4) y/o son has been bugging me quite a bit so we are back at it.

First order of business (at his insistence) "Daddy, we need to put on the wheeeeeeels"

So we set about mounting the tubes and tires. Which took, for-ever. I think the tires are actually the wrong size because they BARELY fit on the rims.

I mean, I spent 30 minutes just trying to get one, onto one half of a split rim before I said, "Berk-it, they don't have to hold air because they have tubes"

And then I did this.

After a trim, they fit on there but were still surprisingly tight.

Oh well. I got em even if it took 3 hours...

When I last left off, I couldn't get the engine to start because I had butchered the plastic body which held the pull starter. I tried to rig up a drill starter but I just don't think it's fast enough for a 2-stroke.

So getting the motor to run again was priority 1.

I had already made these engine stand offs months ago.

So I made a sheet of metal to weld on to them which would hold the pull starter.

Then I found the one I had already made, months ago...

Whatever, I drilled some holes, made a locator tube for the starter and lined everything up for a weld.

I didn't take any pictures, mid process but here are the small brackets welded on and holding the starter.

And... it works! the motor fired right up after a few pulls.

Good thing too, between the engine not starting and the tires being such a pain in the rasp to mount I was quickly loosing interest in this project.

But, we are back on track and hopefully the kids will be driving this before the first snow fall.

I had a whole Sunday free this weekend so I decided to work on the kids-quad some more.

With the pull start sorted, I needed a drive pulley. luckily, I had one sitting around.

This would be where we que up the music. Just use your imagination.

faced and shrunk down first, then add some deep cuts.

The crank shaft on the chainsaw engine is left hand thread and I had to order this for the job.

That would be an M10 x 1.5, 左. I don't know how you pronounce it in Chinese but it's "hidari" in Japanese.

I cut the threads and then "parted" the pulley on the bandsaw. I faced the other side on the lathe, obviously, and then drilled a stepped up hole for the crankshaft.

It went on nicely, just has a bit of a gap to fill between the c-clip and the pulley.

So, I made a spacer and clipped it together. I also added two holes, spaced out the same as my grinder's wrench tool, to make it easier to remove in the future.

Next up, I needed a motor mount to hold it all together. I found these two rubber blocks and drilled them out. I also found some small square tube and cut it in half to make C channel.

After it was drilled and bolted together, I added two stand-offs around the right height.

Then I welded some plate and a bolt onto each one so that I could attach it to the motors bracket I had made earlier.

Lastly, we need a tensioner bracket to go between the frame and engine to take the slack out of the belt.

I did a quick and dirty job making this bracket out of some scrap stainless I had lying around.

After that, I dragged it outside and gave her a few pulls.

It was running pretty rough and wouldn't idle at all but the mounting is working and the belt is turning!  Not bad for a Sunday.

    Nice job, but I wonder, didn't the chain saw have a clutch that  you could have used.  The clutch would make it easier to start and it could idle without moving.

Awesome build!!! I like how you happen to have pulleys on hand.

TED_fiestaHP said:

    Nice job, but I wonder, didn't the chain saw have a clutch that  you could have used.  The clutch would make it easier to start and it could idle without moving.

The big pulley on the back of the bike has a clutch and it was far easier to reuse than the chainsaws'. In the video, it's not idling, it's running at part throttle. Today I got it to idle and it runs slow enough not to engage the clutch. Unfortunately, that's not the case during warm-up. So I will need to prop the back wheels up off the ground during the warm-up phase unless I am able to figure out someway to install neutral. Anybody know of a way to make a super simple belt disengage for neutral?

  Well the way they do it on a lawn tractor, which isn't perfect, there is a lever or pedal that is connected to a belt tensioner.  Neutral is with the belt slack, sorta works, the drive for the  mower  blades, has brake pads that help to stop the blade pulleys with the belt slack.  When you push on the brake you are making the drive belt slack and engaging the brake. 

My oldest will be 5 soon and you've made me realize I want some motorized fun in her life. 

I had some free time for the past few mornings so I was able to get some more work done.

First off, the noise that this thing was making was just unbearable. It had a dinky little box muffler but even that wouldn't fit next to the rear brace. So, I started rummaging around in boxes of old car parts and found, this!

It's the heat exchanger and EGR thingy from a TDI, and it's distinctly exhaust shaped.

So, I made a flange on the mill.

I sanded it down a bit an tried to make it, near flat.

I found that you can color it in with a sharpie, then use a flat block to sand it and find the high spots. I just used the flap wheel to make sure all of the high spots were in the middle around the port and called it good.

If you wanted to do it right, you could use the flat block and a lot of time to make it, for reals flat.

Then, I cut the tube off and made it into a rectangle with pliers.

Then I welded them together. I tried to use the TIG first but I could not get it to work on this stuff without burning through. It's like, soda can thin. So I slowly tacked and added with the MIG.

(you can see where I was practicing on the other section)

Anyway, not bad!

Obviously, it needs some trimming but I will be adding baffles and fiberglass matting inside later.

After that, it was the moment my son has been waiting for. We put the wheels on!

And we finally got to try it out!

I really took my time teaching my son how to use it since he is so young and he did really well. When his sister got home from school, I let her ride it and apparently, he had built up my confidence too much because my directions to her were not that clear and she immediately rolled it over. Whoops... Well, she's fine, doesn't want to drive it anymore though...

Next up, I need to make a belt guard and quiet up the exhaust.

I thought I had been a good Dad to my kids, coaching sports, teaching them to ski and sail... now this comes along.  You're making me feel inadequate.

Awesome job!