Engine Options For a First-Timer DIY Trike Build

First build, first post. I am a super-newb with plenty of book smarts, but I've never done any serious work on anything mechanical.

I have an Atlas Cargo Trike from Sun Bicycles, which is a pretty beefy delivery-type bike. I got it with the intention of throwing on an electric hub motor and upgrading the cargo platform between the back wheels to make this a commuter bike. Unfortunately, the electric rigs are too pricey, and quite frankly so are the kits for gas engines.

When I found a lawnmower at a garage sale up the street for $5, I figured, "what the heck? I could try to work with this for $5." So I started cruising the forums and I got the feeling that the lawnmower engine is not ideal for this. Long story short- I now have a trashed old moped and a working rototiller to draw from as well. Won't have my hands on them until later this week, but now I'm thinking about what direction to go with this.

The trike has a sweet frame holding up the cargo platform at the back. It's got a thin piece of ABS across the top, but the frame is rated for over 300lbs. There is a righteous axle with a sprocket hooked up to the extra-long chain. I would love to hook up a chain/belt driven system right up to the axle, but it's a little crowded for real estate back there unless I make some compromises on the cargo area. So my options kinda look like this:

1. Use the lawnmower engine on a belt-driven system, and use a tensioner to control the speed and let it idle (no clutch on the mower). Might be able to rig up some kind of differential from an automobile to allow me to keep the engine upright and still let it turn the axle directly. This is probably my worst option- the most complicated and labor intensive- however, someone might have an idea on a variation that would work.

2. Use the rototiller engine (four stroke with a clutch) mounted on a plate above the rear platform frame. Keep it on a short belt/chain to the axle and customize the controls (clutch and throttle) to reach the front handlebars. I like this option in theory, but some of ya'll might have feedback on this idea that could change my mind.

3. Cannabalize the moped for engine/controls and mount it the same as in option 2. The main drawback is that I am not sure of the condition of any of the parts, and as far as I know, the thing has been neglected and not running for years.

I might also choose to extend that rear platform frame out further behind the trike and hang the engine underneath. It would preserve the platform itself for cargo, but I would have serious concerns about the front-to-rear weight distribution.

Another option is to try using the brakes from the moped. Not sure how I might accomplish that, but if I could pull it off, it would be a heckuva lot better than buying upgraded brakes for the trike.

Looking for any and all thoughts/suggestions. I promise to stay up-to-date with pictures. Below are current pics of the trike- disregard the kiddie trailer Macgyver-rigged to the back.

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I'm a kit guy so the DIYer is a bit outta my league - but I will say with a rear platform like that to work with you've TONS of potential!

I suppose a 1600 VW would be... excessive tho

There's a few other trikes about on the forum - you'll get it goin' soon I bet

Great project start. I am planning a very similar project this winter, using a heavy duty industrial trike with a large cargo area.
I have a little 110cc childs ATV I am planning on canabilzing for the trike project. It has a Lifan 110cc 4-stroke with electric start and centrifugal clutch.

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There was a time, boy, when I searched for steel, when steel meant more to me than gold or jewels.

nar, 1600 beetle engine would be sick, nut a little excessive

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I FIX MORE THAN I RIDE

welcome to the forum ,there is quite a few trike builders on this site .

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Air is thin up here. Dano 66

Something I came across when stripping a sself propelled Craftsman was the little right angle gearbox that transmits power to the rear wheels- 8-1 ratio and "one way" gears on the ends. You might be able to use one of these to take an upright engine and get wheel drive out of it.