“Like straddling two chainsaws…”
If you love motorcycles, a trip to the Bonneville Motorcycle Speed Trials (BMST) should be on your bucket list. Where else can you see men and women on garage-built machines testing the limits of human ingenuity and perseverance, trying to run at record speed across a dry lake that looks like the surface of an alien moon? Only a few other places on the planet can compare — El Mirage, Lake Gairdner, Uyuni Salt Lake — but none of them have the iconic history of the Bonneville Salt Flats.
We made the pilgrimage in 2021. The friends, memories, and machines at Bonneville have a way of burning their way into the soul. That year, our friend Steve “Brewdude” Garn went into cardiac arrest while kick-starting his triple-cylinder Kawasaki “Purple People Eater,” died, and was resuscitated on the salt — “The Miracle on the Bonneville Salt Flats.”
Today, we’re thrilled to bring you a hand-built land speed racer from a man who was with Steve that day — Fran Carpio of Freakhouse Customs. Fran’s double-engine Yamaha MX80 salt racer was one of the most interesting builds at the recent Handbuilt Motorcycle Show. Only after reaching out to Fran did we learn he was a buddy of Steve’s — the land-speed community is tightly knit, and good folks tend to run with good folks.
Believe it or not, Fran didn’t get his first motorcycle until he was 31, though he’d been building drag cars since high school. Once he found his way to two wheels, however, he didn’t look back. He drag-raced a couple of Kawasaki superbikes before making his first trip to Bonneville 11 years ago.
“After racing across The Salt, all future builds revolved around whether or not that engine could be competitive in a class.”
At some point, Fran became “infatuated” with dual-engine land-speeders, building both a double Suzuki GS1100E and a double Yamaha FJ1200.
When neither builds came to full fruition at the speed trials, however, he rethought his strategy.
“For 2025, I took a step back and built a ‘little’ double-engine bike using the MX80’s. MaXimilian is actually more of a prototype, to see if I could successfully lash a pair of two-stroke engines together and build a reliable race bike. With that mission accomplished, I already have one YZ465 stashed in the garage. Once I find another one, I’ll start building a 930cc double-engined, two-stroke smoker and race in the 1000cc class.”
The engines come from a pair of Yamaha MX80 dirt bikes and remain stock, coupled together with Honda Civic alternator pulleys welded to the stock flywheels and a ribbed belt from O’Reilly Auto Parts, which fit perfectly — no tensioner needed!
Fran designed and fabricated the perimeter frame from scratch, using a 1×3″ rectangular tubing — until recently he had no more than a flux-core welder in his garage! (He’s since upgraded to MIG.) A Yamaha DT250 donated a number of the other parts: wheels, forks, pegs, kickstand, etc.
Every good salt racer needs a name, and Fran christened this one “MaXimilian” after the killer robot in the 1979 film, The Black Hole, which scared the hell out of him when he was nine.
“That robot was badass and I wanted to incorporate the “M” and “X” into the name.”
So how did MaXimilian fare on the salt? Fran took the bike to the 2024 Bonneville Motorcycle Speed Trials last August, where was able to get in one solid run at an average speed of 53 mph, with the GPS speedo showing a peak of 56mph.
That might not sound like a lot, but you’ve got to keep in mind the humble power output and performance of a stock MX80. This run actually represented a 47% increase in top speed.
“I was pleased with that result, as the stock MX80, with one engine, topped out at 38mph with my 180lbs piloting the mini-bike. Both engines are bone-stock, with the addition of Amazon-purchased 21mm flat-slide carburetors. Yamaha rated the engines at 4 hp a piece, but I never claim to have 8 hp. With my gorilla math, I figure I’m about 4 hp x 1.5 for a whopping 6 hp! When we return to the Salt in 2025, I’m going to experiment with some taller gearing with the hope I can see 60 mph.”
What’s more, this home-built machine feels a hell of a lot faster than the mph might indicate.
“If you can get your hands on two chainsaws, head over to a hockey rink, fire them up, and try to run across the ice, one in each hand. The MX80 spins just above 10,000 rpm at full throttle; riding it across the Salt Flats is like straddling two chainsaws. The cacophony of chaos, with the engines belching two-stroke smoke and the belt slinging below your knee and then the drive chain spinning past your ankle is something that has to be seen to be believed…”
We’re wishing Fran great luck on the salt this coming summer, and we can’t wait to see the double-engine YZ465 he’s cooking up. Below is our full in-depth interview with Fran about the build, along with more photos. Godspeed, Fran!
Double-Engine 2T Salt Racer: Builder Interview
• Please tell us a bit about yourself, your history with motorcycles, and your workshop.
I didn’t get my first motorcycle until I was 31 years old in 2001. I had been a car guy, building and drag racing cars since high school and didn’t start my first chopper build until 2009. I drag raced a Kawasaki ZX6R but switched to a KZ1000 when I discovered my love of classic 70’s and 80’s motorcycles.
I had a few more chopper builds under my belt before I took my first trip to The Bonneville Salt Flats in 2014, a visit that would change my life. After racing across The Salt, all future builds revolved around whether or not that engine could be competitive in a class. After a few successful years of Salt Flat Racing, I became infatuated with the idea of a double-engine motorcycle. In 2018 and 2019, I built and raced a double Suzuki GS1100E. I spent 2020-2022 attempting to build a double Yamaha FJ1200, but repeatedly failed to complete the bike before BMST each year.
For 2025, I took a step back and built a “little” double-engine bike using the MX80’s. MaXimilian is actually more of a prototype, to see if I could successfully lash a pair of two-stroke engines together and build a reliable race bike. With that mission accomplished, I already have one YZ465 stashed in the garage. Once I find another one, I’ll start building a 930cc double-engined, two-stroke smoker and race in the 1000cc class.
All of my builds are done in my garage, where I usually have too many bikes and not enough workspace. I’ve gotten by for years with a flux core welder, but have just recently converted it to MIG. I’ve got a portable air compressor, drill press, and a chop saw, but that’s about it for power tools.
I take pride in being a Jack-Of-All-Trades and I’ve even built a collapsible 8’x8′ paint booth so I can paint my bikes in the garage. I try to do as much of my own work as possible, I’d rather do a decent job and take pride in the fact I DIY’d it than pay someone else to do, what is sure to be, a better job than I could accomplish, but I like to be able to say, “I did this”.
• What’s the make, model, and year of the donor bike?
The bike is built around two engines from the Yamaha MX80. According to an online VIN decoder, the front engine is from a 1978 model and the rear engine is a 1977.
• For what class of racing was the bike built?
The bike was built to run across the Bonneville Salt Flats with reckless abandon. Every year, I attend The Bonneville Motorcycle Speed Trials, held the last week of August. I chase the American Motorcyclist Association (AMA) records and the bike was built to run in the 175-A-CF class. A maximum displacement of 175cc with the two engines combined.
A is Special Construction, since the frame is custom built by myself. C is for Classic Engine — any motorcycle motor built from 1956-1980 qualifies — and then F is for Fuel class, which allows me to run any type of fuel (E85, methanol, nitromethane, etc), but historically, I run Fuel so I can just run pump gasoline from the Sinclair station as you exit the highway towards Bonneville.
• What custom work/upgrades have been done?
The engines are stock. The front engine was rebuilt; the back engine has always run so well I never took the time to tear it down. A pair of 21mm PWK clone carburetors from Amazon were had for the low, low price of $26/each and then larger intake manifolds were fabricated.
Alternator pulleys from a Honda Civic were welded to the flywheels and are connected by the shortest ribbed belt we could find at O’Riley’s. An adjustable belt tensioner was originally designed, but once I slipped the belt into position, the distance between each engine was exactly what was needed and the belt is tensioned perfectly. Both engines, while belted together, are started by kick starting the rear engine.
I started by building a fixture/engine mount that would hold the two engines in place. From there I designed a perimeter frame, using 1″x3″ rectangular tube, because I knew I wanted to hang the gas tank inside the frame. The rear triangle is 3/8″ steel tube using the axle plates, foot pegs, and kickstand from a Yamaha DT250.
That same DT gave up its wheels and forks for the cause. The front engine sits higher than the rear engine simply because I wanted each exhaust to stack one over the other. It was one of those times where style won out over function and the overall visual look of the bike took over how the build progressed.
I’m always on the lookout for YZ80 engines, but while they are rated with much higher horsepower numbers, they’re substantially more expensive than buying a whole MX80 mini-bike.
• Does the bike have a nickname?
My favorite movie from back in 1979 was The Black Hole — there was a killer robot in that movie that scared the daylights out of 9-year-old me. Since I was using MX engines, I named the bike MaXimilian.
• Any idea of horsepower, weight, and/or performance numbers?
All the specs I could find claim that a single MX80, measuring 72cc’s from the factory, pumps out 4hp. Now, since it’s really one engine helping the other, I don’t try to double that and claim 8hp, I like to conservatively multipy by 1.5, so I figure I’ve got about 6hp with the engines belted together. Using a pair of bathroom scales, I’m figuring the bike weighs in at about 250lbs.
When I rode my first MX80, I topped out at 38mph on a flat road. Out on the Salt Flats, I averaged 53mph through the measured mile, but my GPS speedometer said I maxed out at 56mph. That’s a 47% increase in speed, which I’m quite happy with. When we return to The Bonneville Motorcycle Speed Trials in August 2025, I’m going to bring some much taller gears and I’m also going to experiment with running E85 and, if that goes well, running methanol as well.
• Can you tell us what it’s like to ride/race this bike?
If you can get your hands on two chainsaws, head over to a hockey rink, fire them up, and try to run across the ice, one in each hand. The MX80 spins just above 10,000 rpm at full throttle; riding it across the Salt Flats is like straddling two chainsaws.
The cacophony of chaos, with the engines belching two-stroke smoke and the belt slinging below your knee and then the drive chain spinning past your ankle is something that has to be seen to be believed. It’s all this crazy noise and vibration, but ultimately, the bike sounds like it’s going much faster than it’s current 50-ish mph top speed.
• Anybody you’d like to thank?
George Gudat for showing me that I CAN do it myself. Rob Dunham for teaching me that building engines isn’t as scary as I thought. Robin Lamberd for explaining to me that simplicity is best, doubly so when dealing with multiple engined vehicles.
The Bonneville Motorcycle Speed Trials, for providing me with the greatest event any motorcyclist could ever attend. If you have the means, I highly recommend getting yourself out there.
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Brewdude is a hep cat, man.
He has had issues since he inadvertently inhaled fumes from burning brake cleaner I believe. . But he is a tough guy.
I used to read his column every month in the Horse Backstreet Chopper.
I was just reading a post of his today as a matter of fact.
The double engine bikes are cool.