Today we’re going to show you some of the craziest and most talked-about motorcycle engine swaps the internet has ever seen. Nasty swaps involving go karts, Ducatis, and Barbie Jeeps… if you’re not inspired to build some crazy bullsh*t in the next five minutes you better check your pulse.
If you think your engine swap should be on this list, email us a video for a chance to be featured in one of our future posts (bonus points for a dirt bike engine swap).
So without further ado, these are 8 Epic Motorcycle Engine Swaps That Shouldn’t Exist and ways to make each and every one of these wild machines street legal.
THE SMARTABUSA
It’s a time to be alive when putting a Hayabusa engine in a Smart ForTwo is considered baseline for crazy motorcycle engine swaps. This recipe has been around for years, and companies like Sinister Sand Sports will even sell you a turnkey swap kit complete with engine, suspension components, and performance upgrades – all the power you want if you’re willing to spend close to $20,000 to get it.
You could build 2 or 3 of the other swaps on this list for that money, and for my money, you definitely should.
YAMAHA BANSHEE RC8R
Right, because a Banshee with a dirt bike engine swap would be too basic.
The KTM RC8R is one of the most menacing track bikes money can buy. Whenever one of these babies rolls into a local bike meet the ground literally shakes – not only from its roaring 1195cc V-twin engine, but also from the sheer force of all the Honda riders shitting themselves in unison.
We suspect the builder did a bit of trickery to get the gearing correct, as the KTM’s 173 horsepower and 90 torques would be pretty hard to manage otherwise. Or maybe it’s just pure insanity… probably a little of both.
DUCATI GROMIGALE
Face it, you knew this one was coming. It’s a heavily modified Honda Grom with the beating heart of a high-end Ducati that’s good for over 200 horsepower. As far as motorcycle engine swaps go, this one’s just nasty.
If you’ve been around for a minute you know this particular Gromigale burned to a crisp after a fuel line ruptured and the whole thing caught fire. A moment of silence for our fallen brother.
But like Buddy Holly and Google Plus, perhaps the Gromigale’s greatest legacy is that it ever existed in the first place. It showed that any motorcycle engine swap is possible if you’re ambitious enough, and the world is still waiting for someone to dream this big again.
Will it be you?
DEMON BARBIESTANG
What you’re watching is a pink Barbie car cutting smoky donuts. Its front wheels are more cambered than a Liberty Walk Lambo, and that four-stroke Honda CRF230 dirt bike engine swap sticks straight through the hood like Dominic Toretto’s supercharger.
Though it doesn’t have a cage or even a seat belt, CarThrottle reports that the builders got this Barbie CRF to 60 MPH in just 6 seconds and finished a quarter mile in less than 16 seconds. Of course, about halfway through this video they nearly throw it off a cliff.
Now that’s the kind of crazy motorcycle engine swap we love to see.
DEMON BARBEEP
Jarbie? Beep? Barbeep? All I know is this is more Barbie paraphernalia than I’ve ever cared about before this very moment.
The premise of this build: take a 250cc Briggs & Stratton engine ($280) and swap it into a kid’s Barbie Jeep ($310) using some cut steel, Chinese brakes, and other assorted goodies (~$300). The result is the cheapest motorcycle engine swap on this list and while it’s not technically from a motorcycle, the result is the Fisher-Price car of your childhood dreams.
You can watch these guys build their own frame, suspension, steering, bearing carriers, hydraulic brakes, and just about everything else needed for a functioning motorcycle engine swap. Then they put a Barbie Jeep body on it and rip around campus. F**king epic.
HONDASAKI KX250 GROM
Take the brakes and chassis from a Grom and throw in the meaty torque of a KX250, and the result is a Grom that “f*ckin’ pulls” thanks to its motorcycle engine swap.
This isn’t the first time somebody had the bright idea to put a two-stroke engine in a Grom, but it’s super satisfying to watch this one doing real work on a track. It’s fast going flat-out in the straights, and it’s so low and nimble that this guy is roping in full-size motorcycles in the corners. Who knew a dirt bike engine swap would make the Grom an all-around better bike?
Check out the build videos for all the juicy details on how this beast came together.
DUKARTI SUPER SPORT
Dirt Legal can get license plates for lots of things – dirt bikes, ATVs, UTVs, and even go karts. We love a good go kart build as much as the next hoons, but for a street legal go kart to keep up with traffic it needs a truly insane engine swap.
Enter the Ducati Death Machine, a 70-horsepower shifter kart where the V-twin engine weighs more than everything else combined. According to the builders “it’s geared for 150+ [miles per hour], but the chance of death is 100%.” Make that 99% and it’s a chance we’re willing to take.
Is this the most ridiculous motorcycle engine swap on the list? You decide.
LIFAN CRF50 125
The Lifan 125 engine is a cheap and simple four-stroke that’s mostly used to power pocket rockets. You know, those tiny things drunk people ride for 5 minutes and get bored of them. But for $330 (shipped!) you can put a Lifan 125 in anything you want, and it makes a killer motorcycle engine swap if done correctly.
This CRF50 is the longtime project of YouTuber Cappamura, and by the end of his building escapades it’s been transformed into a street legal pit bike that’s way too fast for its own good. With some gearing this beast could easily hit 70 miles per hour, the problem is it’s super squirrely.
If you ask us, $300 is a small price to pay for big speed and DANK WOOLIES.
Go build something crazy!
The time is now, people. Bring your epic motorcycle engine swap dreams to life and throw them on YouTube for the world to see. Some of these hoons made enough ad revenue to pay for their swaps, and if your creation is epic enough you can have a slice of that pie too.
We’d love to see a motorcycle bike engine swap where someone puts a street bike engine into a dirt bike, or even a big dirt bike engine swap (like a Maico 620) into a smaller frame. Send it our way and we’ll feature you next time!
Don’t forget to make it street legal!
When it comes time to make that Frankenstein machine street legal, we can make it happen. Dirt bike, pit bike, trials bike, go kart, doesn’t matter - Dirt Legal will get you on the road with a title, tag, and registration ASAP or your money back.
Dirt biking remains a vibrant and evolving culture as we head into 2025. Gas-powered bikes continue to see steady, incremental improvements, while electric dirt bikes are rapidly advancing with lighter components, longer battery life, and impressive torque. Legislative efforts like House Resolution 906 aim to empower riders with the right to repair their own vehicles, fostering independence within the community. Despite restrictive state regulations, dirt biking culture thrives, with growing sales and creative solutions like Montana LLC registration ensuring riders can hit the trails legally. The future of dirt biking is a blend of tradition, innovation, and resilience.