4-stroke gas scooter build

I purchased an electric scooter a few years ago to accompany my wife while she runs early in the A.M.
She is recovering from cancer, and is in remission, and trying to stay healthy.
This town is no longer safe, and just a few years ago, and a few miles away, another woman was murdered doing exactly what my wife does, ie: jogging early in the morning (no we can't move to a safer city; that is not practical).
My knees will no longer withstand running, and our neighborhood is hilly, so while I can bike the route (4 miles), that is a stretch for me.

My electric scooter has been plagued with flat tires, and the tubes are expensive.
The even larger problem is that the electric motor is built into the one-piece rim, and that makes changing the tire much more difficult.
I resorted to using Slime (tm) in the tires, and that helps for a while, but the tires eventually go flat again, and then you have a terrible mess with slime going everywhere when you have to drag the tube out.
Charging the battery requires 12 hours, and while my scooter has a quality Samung (I think) battery, there is always the worry of a battery fire.
And one has to look at the gauge, and guess if there is enough power in the battery to make another ride, or whether it needs charging.
I want to dispense with the battery and charging process.

In frustration, I purchased an inexpensive asian 50cc 4-stroke scooter, and that was a mistake.
The first time I rode it, it shook violently, would hardly pull me up hills, was very loud, and bolts were falling out of it literally all over the engine and scooter.
Total junk; lesson learned.

In desperation, I am building my own 4-stroke gas scooter, and this one will have split rims, so that I can easily change a tube, and readily available and inexpensive tubes and tires.

The smallest Honda motor I could find is a 120cc horizontal shaft, so that is what I purchased.
It is a little larger and heavier than I wanted, but I think will work well since it has 3 hp.

I purchased some rectangular tubing, and and matching the geometry/dimensions of a typical scooter.

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Here is the motor I found.
I think I need this many cc's (120), due to the hilly streets that I ride on.

This is a very high quality motor, and it does not make much noise when it is running.
It is also a well balanced motor with not much vibration.


1st time run, started on the 2nd pull.

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My electric scooter tire when flat two days ago, and I have not had time to repair it again.
It is a royal pain to change one of these tires, and extremely tedious.

In order to try and get this scooter built and functional as soon as possible, I have resorted to using a lot of off-the-shelf go-cart parts and pieces.

I bought a jack shaft and sprockets, along with a 420 chain.
I am gearing this scooter down to it will go at a relatively slow pace to match my wife's running speed.

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I am using a standard go-cart brake kit.
I may upgrade one day to disk brakes, but this brake will work for now.

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1" x 1.5" rectangular steel tube frame.
I opted for a tube slightly on the thick side as far as wall thickness, to make it easier to stick weld.

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I am using a 10" diameter (4.10 x 3.5 x 4) tires made by Carlisle.
Not road-rated, but a high quality tire that seems to run straight and true.

I originally purchased some very inexpensive tires and rims from Harbor Frieght, and while the rims run relatively true, the tires are very out of round, so much so that I cannot use them for anything other than a garden cart or something.

The tubes need to have an L-shaped stem to allow access with a hub bolted to the rim.

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Throttle with cable.
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I always run a kill switch, so I ordered one of those.

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To save time, I purchases a motor mounting plate.
I could not find any sheet metal that I had in my shop that was large enough.

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I am using these rims that came as an inexpensive Harbor Frieght tire/tube/rim/bearing assembly.
I am using the rims, and they will be split type.
I am not going to use the original bearing, but will be using a live shaft like on a go-cart, since I can build that quickly.

I found some go-cart hubs that match the rim bolt holes, and I was able to turn about 1/4" off the exterior of the hub, so that it fit into the rims I had.

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The first night, I roughed out the frame, and got it tack welded.
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The second night I welded the frame, and got most of the welds ground flat.

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I found a flexible sanding disk, and buffed the welds a bit, just to get things a bit more flat looking.
I didn't want just a square end on the tube, so I tapered the ends.

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About a week ago, I started mocking-up an assembly, and figuring out where to put the jackshaft, etc.
The motor has to be able to slide forward to adjust chain slack.
The rear shaft has to be able to slide backwards on the frame, for the second chain adjustment.

For now, I am not using a suspension, since the speed at which I ride is very slow.
If the rides turns out to be too bumpy, I know where I can purchase shock absorbers, and have a plan in mind of how I can incorporate those into the design.

I got side tracked and have been working on a house that I have to sell in the last week, but I think I will get back on this build tonight, and see if I can at least get it rolling, and test the gear ratio.

I am not planning on having a seat; I prefer to stand when I ride, but I could add one later easily enough.

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