GasGas “EC700” Supermoto from Sib Mustard…
For most of us, the Honda CR500 and Kawasaki KX500 represent something akin to the apex predators of the two-stroke dirt bike world — 500cc smokers infamous for their light-switch powerbands, violent soundtracks, and lethal reputations.
Of course, when speaking of such insane machines, any rational hot-rodder has to ask: what if you could…go bigger? After all, for some speed freaks, “fast enough” just doesn’t exist. In the words of Hunter S. Thompson:
“On my tombstone they will carve, IT NEVER GOT FAST ENOUGH FOR ME.” -Hunter S. Thompson, “Song of the Sausage Creature”
Enter our new friend Sebastian “Sib” (@sib_mustard) of Germany’s HAISL — a bike-builder and two-stroke lover who’s earned a large following on social media for crazy customs like the 700cc two-stroke supermoto you see here.
The bike began life as a GasGas EC300, a lightweight two-stroke designed to tackle the gnarly terrain of hard enduro.
“This is the lightest enduro bike I have personally ever ridden… On our scales, amazingly the EC300 weighed in at 106kg [234 lbs] with ½ a tank of fuel in it; even lighter than the spec sheet.” –Planet Knox
But Sib had other plans for the powerplant, modifying the frame to accept the 699cc liquid-cooled two-stroke Mega engine from Austrian company Rübig Motortechnik — an engine designed for sidecar motocross!
This required not only frame modifications, but a custom swingarm, rear shock mount, exhaust, and more.
Sib says he wanted to build a “wolf in sheep’s clothing,” preserving much of the traditional GasGas design language but with a black and copper color palette inspired by the Cupra R.
Aptly enough, Sib has nicknamed this monster the MEGASGAS:
“I wanted to keep the original GASGAS design, hence the large MEGASGAS lettering, but with steampunk elements because it fits well into the color concept.”
Though Sib hasn’t had a chance to get the MEGASGAS on a dyno yet, he says the engine is rated at 84 hp. While you might expect such a big engine to add a ton of weight to the bike, Sib says the Mega engine is only 10 kg (22 lbs) heavier than the original GasGas engine, meaning the bike weighs 115-120 kg (255-265 lbs) — about the same as a CRF450X!
As you might expect, the vibration is enormous — especially since the engine has no balancer shaft — but comfort was never the name of the game when dealing with big-bore two-strokes.
All in all, this is one of the wildest smokers we’ve seen, and Sib is just getting started.
“My next project is already being planned and I will attempt a 2-stroke turbo build.”
We can’t wait, man! Below, talk to Sib for more details on this “EC700” MEGASGAS.
GasGas “EC700” Supermoto: Builder Interview
• Please tell us a bit about yourself, your history with motorcycles, and your workshop.
I’m Sib, and I’ve always loved working on bikes. When I first got my driving license, I also worked on cars a lot. At some point I got back into two-wheeled enduro sports and, through social media, into supermoto sports. I don’t have a workshop where I build bikes to sell; this is my workshop where I only build bikes for my content on social media. Many of my followers only know me through my crazy and detailed builds.
• What’s the make, model, and year of the donor bike / engine?
It is/was a 2021 GASGAS EC300.
• Why was this bike built?
It’s my content on social media, and I often try to make builds that have little precedent or don’t exist. My next project is already being planned and I will attempt a 2-stroke turbo build.
• What was the design concept and what influenced the build?
In terms of color, I was inspired by Nissan Cupra (black and copper). I wanted to keep the original GASGAS design, hence the large MEGASGAS lettering, but with steampunk elements because it fits well into the color concept.
• What custom work was done to the bike?
Mainly modifying the frame so that the 700cc engine fits in. I particularly wanted to preserve the original look of the GasGas (wolf in sheep’s clothing). The damper mount of the special swingarm was also adjusted with special CNC work.
• Does the bike have a nickname?
Yes, MEGASGAS, because it is a GASGAS and the 700cc engine manufacturer is called MEGA.
• Any idea of the weight or horsepower?
It’s just the heavy engine that makes the difference. Otherwise everything is the same as with an original 300 GASGAS. I haven’t weighed it but it’s only 10kg heavier. So around 115-120 kg.
I haven’t been on the dyno with this machine yet, but according to the engine manufacturer, this engine should produce 84 hp.
• Can you tell us what it’s like to ride this 700cc smoker?
It is definitely not a touring bike. This engine comes from sidecar racing and is an old concept, so it does not have a balancer shaft. The vibration is enormous. You don’t want to ride it for a long time.
• Is there anyone you’d like to thank?
My main sponsor HAISL, the other parts sponsors and my followers, who make financing my projects much easier.
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