I've recently completely turned this mower into a new build. If you've read this before, proceed to step 12 for the latest updates. Otherwise, start reading below for the original build. Thanks to everyone who has commented before. As always, feel free to ask questions and I'll do my best to answer. Click Here to proceed to step 12.

In this demo, you'll get some ideas of how you can make a real racing riding mower used in national events. Have fun turning what used to be the family lawn mower into a fire-breathing high speed racing machine. Also- I'm constantly making changes and modifications to the final machine so check back to see what I've done. The next plans I have include steering upgrades.

Please read the following paragraph before proceeding.

Before we start, there's a bit of safety to discuss.Yes, racing lawn mowers from an outward perspective is sort of funny ( which it is!)But its important to realize that racing mowers such as these are heavily modified to handle much greater speeds than the original mower was designed for. Many of these mowers go 50MPH or more.Making a race mower isn't as simple as taking a stock tractor and making it go fast without any alterations. So its important that the frame, brakes, steering, engine, and wheels are modified or altered to handle this additional speed.So to make this point doubly clear, it is NOT a good idea to take a bone stock mower and make it go fast. You can, and will get hurt if you do so, and trust me- I've seen enough people wreck due to this very reason. So play it safe. Secondly, if you do plan on racing, make sure and check out the rules for your chapter and wear appropriate safety gear such as a helmet ( motorbike), gloves, boots, and long pants.My mower is built using ARMA ( American Racing Mower Association) rules and regulations. Lastly, your mower must have an approved jet ski/snowmobile style safety tether switch. If you fall off ( which we often do) the mower must automatically shut down or it'll keep right on going! Racing mowers might seem silly, which it sort of is, but you can get hurt if you're not careful. So be safe!

Ready, let's get started! The 'victim' I chose for this build is a late 60's Grants mower. Tiny little mowers like these were produced back when riding mowers were still deemed a luxury. They're little more than a seat sitting on top of a mower deck. Most used smaller engines. The advantage of using such a little mower is that you can reduce the weight dramatically by simply having a 'legit' riding mower complimented with a larger engine, hence a higher power/weight ratio. Don't get attached to it. When its done, there won't be much left of the original.

The first step is to strip the mower down to the frame. Modern mowers usually have a single stamped piece of steel. Older mowers like this one have frames made of square tubing or slabs of steel. This will give you an idea of how much of the mower is actually usable and how you can lay out the drive, steering, and brake components. Besides the hood, what's leftover to use isn't much. The rest are worthless such as the stock wheels, steering wheel, and transmission.
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I have been told you have to watch where you take meat off inside the head when your porting a head. I have heard this can actually make the engine put out less power if not done just so. Is this true ? Do you have to be expert at it , or just know the basic goal ?

You also mentioned you wasn't sure of the gear ratio. To figure the gear ratio you simply take the larger gear which i think you said yours was a 40 an divide the smaller clutch gear 14 thus giving you a 2.86 gear ratio.
If you decide to up your cam to a performane cam check out dyno cams they work great easy to set up an they will be glad to help you with your timing valve springs and differnt spring tensions as all this will play a role with an aftermarket cam. I would also suggest investing in a dagree wheel if your modifing yourself your going to need one. BMI karts is also an excellent kart shop to buy any frame components you may need in the future affordable prices. Turk bros. For any of your engine parts. I have built many karts an racing engines over the years an these places work well for service an price. I wish you the best hope this may help out. Feel free to email me with any engine questions b glad to help.
FredB21 month ago

how did you connect the engine to the gear box, do you have pics on that

if you put a 9 inch pulley on the front and a 3 inch on the back you would have to custom your belt but how fast would that ratio go 9:3

nishant222 months ago

I wan to make a electric car for mech project I need a dc motor less than equal to 3000 w max rpm 3600 max torque 12.8nm at 2400 rpm power consumption max 48 volt can u recomend me some motor name or link which would suit best for me....thanx in advance...

miller03054 months ago

What kind of welder will work for welding on the frame?

Ohioeightytwo8 months ago

I am not sure which is more impressive; your project or your very excellent narrative. My compliments on both efforts.....

BUTTERMAN10110 months ago
My uncle has a 340cc 4 stroke and my dad has a 370cc 2 stroke which one
Should I use and I am using one of these engines
For racing can I have some
Im working on building a race mower and im wondering how the build will cost
Depends how crazy you go on it. I spent $1000 build a mower, and that wasn't anything fancy. As well, since I went with fairly cost effective solutions it did not adhere to racing lawnmower specs so it can't actually be raced, however that was never my intention so that was alright.
BUTTERMAN10111 months ago
What kind of engine and what size did you use
For your mowers
Depends if you actually want to race it in mower racing competitions or just use it as a hooligan tool. Racing there are very specific rules you have to follow to be able to compete, and you would have to research these as there are several race types based on modifications, engine displacement, etc. If you are using it as a hooligan tool, you can do whatever you want. I used a 340cc twin 2 stroke from an older snowmobile running around 40hp which worked quite well. Using a non-stock engine to your tractor is more difficult though because you need to modify the drivetrain. I had to completely machine a new system for mine, brackets welded on for bearing supports, shafts machined, sprockets, chains. Real pain in the ass was odd sized shaft needed for the secondary clutch. The stock engine is best to go with in my opinion.
BUTTERMAN10111 months ago
How many mowers do
You guys have?
BUTTERMAN10111 months ago
Hay I'm a ten year old
Kid and I always wanted
A Lawn tractor do any
Of you guys/girls now
Anybody in Nova Scotia
With a lawn tractor for sale
Let me know Thanks
IT-Jack1 year ago
how to fast does it run?
This is a great Instructable, but you need to add a main image for the project!

Please do that, and reply to this comment so I know when you are done.

HammE1 year ago
Wow! Just gave me another thing to think about building!
What kind of clutch did you get and where did you get it?
When you upgraded the stock starter to a high torque model, how did you determine which one to buy? I have a Tecumseh 36680 starter that needs to be replaced and am wondering if I should upgrade it to a better version. Here is the stock:
florman2 years ago
Hey I want to make a racing mower and was wondering if you could take look at this mower i found for sale near me and tell me if you think it would be a good choice as a racing mower


Its a Wizard dont know the year
SimonK952 years ago
We are currently working on a 14.5hp engine, and we have fully stripped down the body and lightened it all, But we don't know hope we change the gearing on it? Any advice would be great, but make it sound simple, as this is our first build? Engine is an Intek so advice would be great?
Wesley6662 years ago
Current racing mower. It does not meet any of the American Racing Mower Associations rules and regulations, for any class because its a high power, 2 stroke from a snowmobile, as well, there is only one class I believe that allows the CVT clutch and transmission it has to be legal. Mostly wanted to make it for the hell of it, see how fast I can get this thing to go (I want it to for sure hit 120km/h, but that is really quite easy for the engine I am using).

Also, bought a different engine then I intended to use. I planned on using an 110hp Arctic Cat engine, but I am selling it and using this little 30hp 340 instead, seemed a little more reasonable. I want to lower this mower in the back, use wheels only slightly larger then the front instead of the big ones that came on it (Also because I am custom making the whole drivetrain, I can make it to whatever wheel size I want) and I want to keep all the body panels on, but adjust the main one so the seat sits lower.

The drivetrain that came off this has both a high speed 90 degree gear box which would be great for a lawnmower engine to get it driving a shaft horizontally, as well as a 4 speed w/ reverse transmission with differential. The transmission is bullet proof, solid cast iron construction. 1st gear has loads of power, if you punched the pedal you could get the front end of the tractor to come way up off the ground, 4th gear without mods would run this tractor up to about 50km/h. I would like to use the transmission in a go kart sometime with a manual clutch, I could make a mean racing machine with that setup.

Old lawn tractors are by far the best lawn tractors you can get, do a pulley swap and tune the engine, you could probably hand a lot of people their mowers on a silver platter with a near stock machine.
billybob63 years ago
whats the eaisiest way to reinforce the frame because i cant weld
also, the best way to learn to weld is to practice on scrap metal. under the mower don't have to look pretty as long as it holds. just remember, DON'T weld it all the way, stitch weld it so you don't warp the frame. i live in N.E. and we build mowers that can go 100 mph+
Sorry Pal, ain't no mower gone 100 mph yet.
I see nothing to indicate this "mower" reached 100 MPH and sustained that speed. Bobby Cleveland driver and racer, sponsored by and employed by Gold Eagle went to the Bonneville Salt Flats (twice) and still was unable to reach 100, but he was close. The video can be seen on the USLMRA website. My brother, Chuck Miller, was there as part of his pit crew for the attempt. Bobby's speed was documented by the Salt Flat organization. So a claim is only a claim unless you have bonafide documentation to back it up. Video of a machine running illegally on a public road doesn't cover it.
I just realized though, you probably have to use a stock engine that has been upgraded, not transplanting a monster of an engine into them, correct?
No one has gotten a lawnmower to do 160km/h? Seriously? I just picked up a 110hp sled engine from a 2004 Arctic Cat Sno Pro and was planning on putting it in a lawnmower to motor around on. If you can get a sports bike to hit 200km/h with less then that I think I can get a lawnmower to do 160km/h. Clearly, no one has really put in a good effort to get a lawnmower to go balls out. I think I could get a lawnmower up to 200km/h easy with 110hp.
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And your comment is backed by what????
i have found the best way to reinforce the frame is to use 3/4 square stock along the top corner of the frame. this will make the frame very strong but not add to much weight
i have looked all over for a ragb and can only find either reducers or 1:1 ratio boxs, but most are only rated for 2hp and at a costly $250. could you please give me the specs on your ragb and where you got it.
go on ec distributing. go on mower parts and the very right bottom link will say right angle gear box. or get a peerless 1100
go on heymow.comgo on find a p-91
i was wondering if i take the pulley from the back and connect it to the engine and the pulley on the engine to the back would it make it go faster
aswracer2 years ago
i have a old mtd with 6 speed stock i wanted to know how to make it work for speed?
go on hey otherwise just take out the factory grease and reverse chain and add some realy good grease of gear lube
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