Turning Lawnmowers Into Yard Karts

Carl
By Carl Heideman
Sep 15, 2021 | DIY, lawnmower, Cheap Fun, Yard Karts | Posted in Shop Work , Features | From the June 2010 issue | Never miss an article

Story and Photography by Carl Heideman

Life is a funny thing. By the time that you’ve got the tools, skills, space and money to do some seriously cool things with your cars, you’ve probably got a family, too. While family is wonderful, it can use up all of the time you had once planned to spend in your well-equipped shop.

We’ve found a grassroots solution to this problem: Make a vehicle out of junk with your kids.

We’re talking about grassroots go-karts here. They can scratch your tool-time itch and make you a better parent at the same time. And when we say “make a vehicle out of junk,” we really do mean old junk. Our favorite chassis for these home-built yard karts come from cast-off riding lawnmowers.

Note that we’re not talking about serious karting or racing, just backyard stuff. Our goals are to spend quality time with our kids, expand our own fabricating skills, and maybe teach the rest of the family a few things at the same time.

Grassroots go-karts can open up a whole new world for you and your kids. Instead of going to the local pick-your-part, you’ll be hitting up the nearby lawnmower junkyard. Your craigslist searches will go a little further—your kids can even do them for you, and as a side benefit they’ll learn to spell new words, like “centrifugal.” You’ll find new Web sites and message boards to frequent. You may even end up buying or making a new tool or two.

 However, the real fun is in the vision, the fabrication and the rides. You’ll quickly find yourself looking at lawnmowers, weed whackers, leaf blowers and chain saws in a much different light. Your kids will keep the ideas coming, and the rest of the family won’t roll their eyes when you head off to the garage.

Know the Basics

Your kids aren’t going to think riding around on an old mower is that cool, so some demolition and construction are in the cards. First, though, it helps to have a basic understanding of the components involved.

 

Engines:

Most non-racing go-karts are based on bits and pieces from small engines. Think of the ones powering lawnmowers, snow blowers and other yard implements. We prefer to use four-cycle engines for our karts. 

While there’s always a temptation to go for big power, we’ve found that 3- to 5-horsepower engines offer plenty of oomph in a small, light package. These engines can propel our yard karts to 25 mph, and to be honest that’s fast enough for our tastes. 

Engines come in two basic varieties, with either a horizontal or vertical crankshaft. The configuration determines where the drive output is located—on the side (horizontal) or bottom (vertical) of the engine. 

Vertical shaft engines are much more common—just about every push mower has one—so they’re usually cheaper. They also seem to come with more updated features like overhead valves. However, horizontal shaft engines are often easier to install and set up with a clutch and chain.

Clutch:

Now the power has to be transmitted to the wheels. The easiest way to do this is with a centrifugal clutch mounted on a horizontal shaft engine. Clutches are available in all shaft and chain configurations as well as belt-drive varieties. Prices start at about $30 and can exceed $100—we’ve gotten good results with the cheap clutches when they’re properly lubed. 

The next rung on the ladder is a torque converter setup, which is basically a centrifugal clutch and variable-speed transmission. Torque converters work with cones that move in and out, first letting the belt slip before changing the effective pulley ratio to alter the speed of the final drive. They cost more—figure $200 and up—and require more space and fabrication to install than a centrifugal clutch. However, they’re a good solution if you think you crave a faster kart.

Transmissions and Drive Systems:

Our favorite is the ubiquitous Peerless unit, offered by the company that makes Tecumseh small engines. It’s found in many rear-engine riding lawnmowers as well as walk-behind snow blowers. There are several versions, but most are close-ratio five-speeds with a sequential shift pattern and reverse. 

Newer ones have a neutral safety switch, and some feature a small disc brake. We’ve stayed away from transaxles because they’re bulky and harder to package, but we have seen them used successfully.

While belt drives are possible, a chain is a cheap, easy way to get power to the wheels. If you’re using lawnmower parts, just reuse the chain and gears. You’ll find that you can mix and match gears sourced from junk mowers to change ratios if necessary. 

Chains come in a variety of numbered sizes, and the most common sizes seem to be 35, 40 and 41. Your lawnmower shop or some Web-based suppliers can help sort out the sizing and bits needed for the chain. While a chain-breaking tool can make it easier to lengthen or shorten the chain, we’ve found that a grinder and quick-release connecting links can work well, too.

Differentials:

A lot of cheap go-karts are one-wheel drive, while most racing versions have a solid, locked axle. Riding lawnmowers, on the other hand, have differentials. 

Again, Peerless is the name most commonly found on these units, and we’ve used them several times. Most are traditional gear-type differentials, meaning they’ll allow for a lot of slipping. Even so, that’s still better than one-wheel drive. 

We’ve found that some of the budget-priced riding mowers feature spring-loaded pucks in their differentials, and these actually seem to work as low-buck limited-slip units. If you find one, you’ve got a hotrodded kart in the making.

Brakes:

The most primitive brakes are scrub brakes—metal flaps that rub against the tires. While they work okay, we prefer more elegant solutions such as band, drum and disc brakes. Most riding mowers use one of these setups, and adapting them to a kart is pretty straightforward. 

The low-buck solution: Grab something from the biggest junked mower you can find. If you want to go a more sophisticated route, the mail-order kart supply houses will have some good solutions. We’ve seen simple drum brake setups for less than $100 per corner.

Steering:

We often just adapt lawnmower steering components, retaining the basic geometry with maybe a few tweaks. This step can involve some fabrication, as we typically section the mower’s spindles to lower them. 

This is a great time to discuss chassis setup and steering with your kids. In no time they’ll be tossing around terms like “Ackermann,” “caster” and “camber.”

Wheels: 

Riding lawnmowers use wheels of nearly every size, so you can usually mix and match to get the desired look, handling and speed. Most mowers use a 5/8- or 3/4-inch shaft, so fabrication is rarely part of the mix-and-match routine.

Linkages:

Expect to modify and fabricate the brake linkage. You’ll probably have to tackle the clutch, shifter and throttle linkages, too. We like to use lawnmower leftovers for those first three jobs; for the throttle linkages, a bicycle brake or derailleur cable should work perfectly.

Donor Junk

We’ve found that smaller, rear-engine riding lawnmowers make great donor junk for a grassroots go-kart. We’re especially fond of some of the older Toro and John Deere models that feature simple folded chassis. (We tend to avoid mowers made up of complex stampings.)

Our preferred chassis generally come with engines that are too big and heavy for our tastes, so we often mount smaller engines. As a bonus, most of these mowers already have five-speed Peerless gearboxes. Brakes, steering and even wiring can often be modified and reused, so these mowers give you most of what you need to get started.

If we’re ditching the big engine on a rider, where do we turn? When opting for a centrifugal clutch and no transmission, we look at smaller horizontal shaft snow blowers, leaf blowers, pressure washers and chipper-shredders. If we’re going for a transmission, then just about any vertical shaft push mower will do the job—we prefer examples with overhead valves, though.

A bonus option is an electric start. Some push mowers feature a starter and charging system, though this setup does require a battery. Some snow blowers use similar systems, while others use 110-volt starters that only work with power cords. If you want to spoil your kids—or save your own arm—look for electric start.

There are myriad other options when it comes to finding donor junk. We recommend getting friendly with the local mower junkyard—every town has one—to scout and dream up ideas. The mower junkyard is going to charge more than the real grassroots sources, but the convenience may be worth it.

Finding Said Junk

While the local mower junkyard can be a great parts source, the real bargains are found at garage sales and just out by the curb. We’ve picked up many project starters at garage sales, usually for $5 to $20. If the junk doesn’t run, it’s probably not worth more than $10. 

We’ve also received many things for free when people know the kids are involved. We actually prefer to get stuff that doesn’t run because it’s cheaper and provides more teaching opportunities. 

The fixes are usually pretty simple. Probably nine out 10 non-running engines that we see just need their carburetors cleaned or their gaskets replaced.

Better and Faster

Of course, sooner or later a grassroots go-karter is going to start tweaking the engine to make more power. Whether you’re talking about a small engine or a big-block V8, the best gains come after some careful planning.

First of all, keep in mind that mower engines differ from car engines in that they’re optimized to run at one speed, usually 3600 rpm. Since horsepower equals torque times rpm, an easy way to get more power is to increase the speed of the engine. Some engines will handle more rpm just fine; we’ve had an OHV Briggs engine running past 5000 rpm for several years. Others, however, grenade pretty quickly when they get buzzed to a higher rpm.

The lawnmower bench racing community first recommends removing the governor. We generally agree, but with a few conditions. Remember that the governor’s job is to keep the engine running at 3600 rpm so the mower can handle a lawn’s rough spots.

If you have a younger kid, you may actually find that retaining the governor keeps things smoother. On the other hand, if you want snappier throttle response and a simpler linkage, bypass the governor. 

If you decide to do without the governor, be cautious regarding wide-open throttle. While conventional wisdom says that WOT is desirable, it may over-rev the engine and send you back out to the mower junkyard.

You’ll also need to modify the gear or pulley ratios. Mowers are geared for power at low speeds. Since you’re not cutting grass anymore, you can increase the pulley ratios and speeds without worrying about having enough power. 

If you’re using a centrifugal clutch and a chain, you’ll want to shop for a smaller gear for the axle. (Most centrifugal clutches come with one gear size, so you’ll need to work with the gear on the axle.) 

If a transmission or belt drive is part of your plan, it’s easy to swap around pulleys to get a ratio that delivers the desired speed and power. You can also alter tire size to optimize power and speed, as taller tires give a higher top end. It’s a trade-off, however, as tall tires typically hurt acceleration. 

We always start with a pretty slow ratio to keep our kids safe, then increase slightly as necessary. As a bonus, the kids learn some math as they figure out how pulley ratios and gear ratios affect acceleration and speed.

Get Out There

If it sounds like we’ve overthought grassroots go-karts in an effort to find every possible trick, we plead guilty as charged. We’re always after getting the best stuff for the lowest price, so why shouldn’t that apply to lawnmowers and go-karts?

These simple karts may not win a national points race, but they’re neat, handy tools that can be made out of junk. Now go build.

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Comments
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Professor_Brap
Professor_Brap GRM+ Memberand Dork
2/25/20 8:32 a.m.

I'll snap some pics of my old wheel horse we turned into a yard cart. It's got a 212 predator that's been worked over in it. It's uncomfortably fast. 

Durty
Durty Reader
2/25/20 8:38 a.m.

Awesome article rehash. I love the ideas

volvoclearinghouse
volvoclearinghouse PowerDork
2/27/20 8:27 a.m.

When I was in college, before I had a car, I would buy running lawn tractors for $100, scrap the deck, swap pulley's, and go screaming around campus at 20-25 mph (we timed it) and get pulled over by campus police.

I just got an old 8 horse crapsman rear engine rider running that I have no use for, and a soon-to-be six year old daughter who's aching to get on something self-propelled.  devil

Aaron_King
Aaron_King PowerDork
2/27/20 10:36 a.m.

I showed this to my 12 year old, he has big plans for the Spring.

Carl Heideman
Carl Heideman
2/27/20 8:13 p.m.

I wrote that story about 10 years ago, so here's the epilogue.

That lawnmower junkyard finally closed about 2 years ago.  We have another one, but it's not anywhere as cool as that one was.

Both of my sons really learned from those karts and moved onto cars.  My older son has built an S-52 powered E30, a Miata with a $100 Mercedes supercharger, a turbo Miata, and a CAM-T Falcon wagon.   My younger son has built a turbo NB Miata and is helping on all the family car projects.  My daughter took a few rides in those karts and decided that she's going to save the world from transportation-based problems.  So she's equaling us out and we're considering our family carbon-neutral.   We've all bonded because of those projects and there were many educational opportunities from the ups and downs of these projects.

buzzboy
buzzboy Dork
2/27/20 10:17 p.m.

I had a sweet hydrostatic lawnmower that would have made an incredible Z-turn go-kart but sadly hurricane Sandy took it from me. I still lust after that concept.

_
_ Dork
2/27/20 11:36 p.m.

One of my favorite memories of owning a John Deere rider was pedal to the metal forwards, followed by an immediate slam into reverse. Rocking horses on a greased up garage floor. And it took it all day with a beer in hand. 

GIRTHQUAKE
GIRTHQUAKE HalfDork
2/28/20 1:52 p.m.

I don't need another project.

I don't need another project.

I don't need something to pull project cars.

I don't need another project.

Woody
Woody GRM+ Memberand MegaDork
2/28/20 2:14 p.m.

 

After seeing this photo in the article, I Googled John Deere R72.

 

 

I don't think I've ever seen one of these things, or anything even remotely like it, which is probably why I've always had such a hard time envisioning this concept. I wonder if that style of mower is some kind of regional thing.

Indy-Guy
Indy-Guy PowerDork
2/28/20 3:41 p.m.

I think you've just convinced me to do something with this derelict mower:

Indy-Guy
Indy-Guy PowerDork
3/15/20 5:00 p.m.

Getting started:

 

Indy-Guy
Indy-Guy PowerDork
3/15/20 5:22 p.m.

Disassembly is up first:

Indy-Guy
Indy-Guy PowerDork
3/15/20 5:44 p.m.

This is what we're working with on the bottom side:

Recon1342
Recon1342 HalfDork
3/15/20 6:02 p.m.

Oh, boy!

Dieselboss15
Dieselboss15 New Reader
5/4/20 4:04 p.m.

Can I use a centrifugal clutch and a 5 speed trans?

ckosacranoid
ckosacranoid SuperDork
5/4/20 4:38 p.m.

There is some youtubers that are doing stuff like this all the time and building mowers to take the place of 4 wheelers and off roading them. I think there are Facebook groups also and forums also for this. cool to see and thanks for sharing...though you do have me thinking about something like this for the challenge and turning into a zamboni to be able to bring it down.......damn you for that...much cheaper then a car at least.

Dieselboss15
Dieselboss15 New Reader
5/4/20 4:41 p.m.
GIRTHQUAKE said:

I don't need another project.

I don't need another project.

I don't need something to pull project cars.

I don't need another project.

angrygaaaaaaaaaaaaahhhhhhhhh

Dieselboss15
Dieselboss15 New Reader
5/4/20 5:48 p.m.
Aaron_King said:

I showed this to my 12 year old, he has big plans for the Spring.

just a couple years older than him, me too! have to find one for sale first tho.

Woody
Woody GRM+ Memberand MegaDork
5/16/20 7:16 p.m.
Woody said:

 

After seeing this photo in the article, I Googled John Deere R72.

 

 

I don't think I've ever seen one of these things, or anything even remotely like it, which is probably why I've always had such a hard time envisioning this concept. I wonder if that style of mower is some kind of regional thing.

Whenever possible, make gravity the Coyote's greatest enemy.

 

Cheap, but too far away. Not to mention the fact that Greenfield is Dead to me.

https://www.facebook.com/marketplace/item/565356721068215

oldopelguy (Forum Supporter)
oldopelguy (Forum Supporter) UberDork
5/16/20 8:30 p.m.

Functionally those deeres are the same as a manual transmission Snapper with respect to building a kart out of them.

Crackers
Crackers Dork
5/16/20 11:32 p.m.

I've been musing over the idea of turning my old riding mower into a "minibike" style trike. Or a utility vehicle with a dumping hopper on the front. Or a ghetto Pullmax style sheet metal shaper/planisher. 

The trike would probably be the most fun, but the least practical.

Indy "Nub" Guy
Indy "Nub" Guy PowerDork
6/13/20 10:38 p.m.

Finally got some more progress going on this tonight.  Taped a line to cut and extend it a bit...

Both boys were doing their best Frieburger impression while taking a turn with the death wheel:

Cut and ready to weld in an extension:

Here's the transmission:

We pulled the gear lever to put it back on 180 degree, which will allow the seat to be placed rearward a few more inches.

Indy "Nub" Guy
Indy "Nub" Guy PowerDork
6/17/20 9:30 p.m.

I used some bed frame rails for the frame extensions.

Then we tacked on the seat and they're getting excited.

The boys wanted Indy-wife to come out and take a look, so she snapped this pic of us:

Indy "Nub" Guy
Indy "Nub" Guy PowerDork
6/18/20 7:12 p.m.

Ok guys, need some help with this.  Mouse chewed up the plug wire.  How do I fix this?  Or is it time to buy a new Magneto?

Carl Heideman
Carl Heideman
6/18/20 8:55 p.m.
Indy "Nub" Guy said:

Ok guys, need some help with this.  Mouse chewed up the plug wire.  How do I fix this?  Or is it time to buy a new Magneto?

That's easy:  You go to the local lawnmower junkyard, take your kids, take apart another engine, remove the used magneto, and your kids bargain with the junkyard owner.  He'll start at $10, they'll walk out for $1.  They learn mechanical skills and negotiating skills, and you get credit as a great dad for teaching them.

Justjim75
Justjim75 Dork
6/18/20 10:55 p.m.

Gloves and shoes!

volvoclearinghouse (Forum Supporter)
volvoclearinghouse (Forum Supporter) PowerDork
6/22/20 6:52 a.m.

Yesterday (Father's Day, fittingly, I started work on this little Craftsman ride the kids had been putting around the yard on.  The biggest issue is they can't reach the pedal...

volvoclearinghouse (Forum Supporter)
volvoclearinghouse (Forum Supporter) PowerDork
6/22/20 6:53 a.m.

By bedtime last night, it had progressed to this:

volvoclearinghouse (Forum Supporter)
volvoclearinghouse (Forum Supporter) PowerDork
6/30/20 10:22 a.m.

Took it out for the inaugural spin around the yard a few days ago.

Never before has so much fun been had at 2-1/2 mph.  laugh

Got a few more things to do...clean up the wiring, dress some sharp edges, and of course the important thing- figure out how to dress it up and paint it. 

Daughter gets adventurous and takes it into the woods.  She's...mostly on the path.

Maniac0301
Maniac0301 HalfDork
7/1/20 10:40 a.m.

I hadn't realized people carried on in the comment section of this article its great seeing everyone's creativity.   So should we setup a GRM $200.20 lawnmower challenge class?   I setup a build thread for my kart project at:

https://grassrootsmotorsports.com/forum/build-projects-and-project-cars/maniacs-john-dyr-yard-cart-summer-project-with-the-spawn/174023/page1/

earlybroncoguy1
earlybroncoguy1 Reader
9/15/21 5:17 p.m.

OK, I didn't exactly make a go kart out of a lawnmower, but I did hot-rod a Power Wheels truck for my kid:

Started with a Power Wheels Bigfoot monster truck a neighbor was throwing out - dead 6 volt battery. Cleaned it up, took all the decals off, gave it a paint job. Fabricated a rear suspension subframe out of angle iron and worn out minivan liftgate gas shocks, with hardware springs around them to turn them into coil overs. Front spindles got springs around the uprights for a basic suspension. Used a garden tractor size 12 volt battery, installed under the seat, wired into the dual 6 volt motors on the rear wheels.

I tell you what, 12 volts going through little 6 volt motors sure made it fun. Plus, that big battery had plenty of capacity, it would run for hours. I'd charge it overnight, take it and the boy to the local park, and he'd run all over. Literally - he ran over stuff. He figured out pretty quick if he got going full speed in reverse, then flipped the forward/reverse toggle switch, the momentum and power surge would result in a pretty impressive wheelie.  

David S. Wallens
David S. Wallens Editorial Director
9/16/21 8:31 a.m.

Love seeing all of the homebuilts. Yes, please keep sharing them. 

psteav (Forum Supporter)
psteav (Forum Supporter) Dork
9/16/21 11:36 a.m.
earlybroncoguy1 said:

OK, I didn't exactly make a go kart out of a lawnmower, but I did hot-rod a Power Wheels truck for my kid:

Started with a Power Wheels Bigfoot monster truck a neighbor was throwing out - dead 6 volt battery. Cleaned it up, took all the decals off, gave it a paint job. Fabricated a rear suspension subframe out of angle iron and worn out minivan liftgate gas shocks, with hardware springs around them to turn them into coil overs. Front spindles got springs around the uprights for a basic suspension. Used a garden tractor size 12 volt battery, installed under the seat, wired into the dual 6 volt motors on the rear wheels.

I tell you what, 12 volts going through little 6 volt motors sure made it fun. Plus, that big battery had plenty of capacity, it would run for hours. I'd charge it overnight, take it and the boy to the local park, and he'd run all over. Literally - he ran over stuff. He figured out pretty quick if he got going full speed in reverse, then flipped the forward/reverse toggle switch, the momentum and power surge would result in a pretty impressive wheelie.  

Dude, you're way more ambitious than I am.  I took a 12V power wheels Escalade I got off of FB Marketplace for $20, wired in a battery plug for my Dewalt 20V drill batteries, and then gave it to my kid. It's fast enough in "high gear" that he's afraid of it.   Thankfully, it's traction limited by the slick plastic wheels...cause I'm not sure my fat ass could catch it if he took off in high towards something dangerous.  

Also, did you know a Power Wheels turned on its side in a full pickup bed basically becomes a giant airfoil at 55 mph?  I sure didn't!  

Unrelated, anyone got a hood for a Power Wheels Escalade they'd be willing to ship?  Asking for a friend.

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