Speedy Siegl’s methanol-fueled, nitrous-injected 100cc land speeder!
This past summer, we were fortunate to make the journey across the country to the Bonneville Salt Flats outside Wendover, Utah, for the 2021 Bonneville Motorcycle Speed Trials. It was everything we’d hoped and more. Incredibly warm and welcoming folks, insane machines, and a truly staggering backdrop — Mad Max meets Tatooine at 200+ mph!
Recently, we heard from our friend Isaac Siegl of Speedy Siegl Racing, whose street-legal RD350 “Dream Racer” and 100,000-mile DR-Z400 we’ve previously featured. This year, Isaac took on a new challenge: building a land speed bike to compete at Bonneville!
“I built this bike to break a landspeed record! After years of prodding and encouragement from other friends who have tried it, I was finally convinced to find a record I felt like I could compete against, and built this bike to beat it.”
The class/record Isaac chose was 100-MPS-PF, meaning modified frame, partial streamlining, 100cc, pushrod actuated valves, and any fuel besides regular gasoline. His donor was a humble 1964 Honda CT200 — the predecessor of the CT90 — though he ultimately went with a C200 frame for the larger backbone, which made it easier to conceal the fuel pump, nitrous solenoids, and other go-fast goodies.
Design inspiration came from 1960s-70s 50cc GP bikes, as well as Japan’s B.O.B.L. (Battle of Bottom Link) 50cc leading-link racers. Isaac says everything but the hubs is scratch-built or modified. The cylinder was bored 3mm to fit a modified CB175 piston for higher compression, and the crank, primary, cam gear, and rockers were all lightened. The head was ported, a second spark plug hole added, and Web Cams provided a custom camshaft.
“The engine inhales through a Mikuni TM24 flat slide carb tuned for methanol, and a wet nitrous system. It exhales through a handmade tapered stainless steel exhaust.”
The bike is now rolling on 18-inch Excel aluminum rims and uber-slim Bridgestone BT39ss tire, and the custom aluminum tanks holds the nitrous bottle. For better aerodynamics, Isaac whipped up some rear wheel discs and outfitted the bike with a 1970 Kreidler GP50 fairing. We especially love the Lucky Strike-inspired livery, a nod to Kevin Schwantz’s 1980s superbikes.
The bike weighs in at just 135 pounds! Though the tall gearing translates to slow initial acceleration, the bike opens up after 7000 rpm:
“At Bonneville it doesn’t have enough power naturally to pull 4th gear, so that’s when nitrous gets involved! After hitting that button, the bike changes tone completely and pulls harder than ever!”
In its very first visit to Bonneville, the “Speedy Seagull” set a new class record of 73.75 mph in the timed mile — quite the feat of engineering for such a small displacement machine. Below, we get the full details on the build from Isaac himself, as well as more gorgeous shots from photographer Taka Masui (@takamasui_photography).
Honda CT200 Land Speed Racer: Builder Interview
• Please tell us a bit about yourself, your history with motorcycles, and your workshop.
My name is Isaac Siegl, and I have been building motorcycles for 16 years. I now have a small business manufacturing lightweight parts for vintage and modern classic motorcycles.
• What’s the make, model, and year of the donor bike?
The original bike I bought was a 1964 Honda CT200, the predecessor of the CT90. I ended up using a C200 frame though.
• Why was this bike built?
I built this bike to break a landspeed record! After years of prodding and encouragement from other friends who have tried it, I was finally convinced to find a record I felt like I could compete against, and built this bike to beat it.
• What was the design concept and what influenced the build?
The design is heavily influenced by the B.O.B.L. (Battle of Bottom Link) racers of Japan, as well as the 50cc GP bikes of the 60’s and 70’s. The AMA landspeed rulebook also influenced what I needed to do and what I was allowed to do. There are many regulations!
• What custom work was done to the bike?
Everything except the hubs has been modified or made from scratch on this bike. The most modification was done to the engine, which had its crankshaft, primary, cam gear, and rockers lightened. The cylinder was bored 3mm larger and a modified Honda CB175 piston was used for higher compression.
The head was extensively ported and a second spark plug hole was added. A custom camshaft from Web Cams was used, and an ignition system was improvised using a Pertronix Hall effect system and a dual output coil from a Harley. The engine inhales through a Mikuni TM24 flat slide carb tuned for methanol, and a wet nitrous system. It exhales through a handmade tapered stainless steel exhaust.
The frame was changed to a C200 in favor of its large backbone and lots of space inside the frame to hide things like the fuel pump, nitrous solenoids and relay, coil, etc. All the brackets to hold everything were fabricated including the gauge pod, fairing brackets, foot controls, seat mounts, frame covers, chain guard, and more. The original chrome rims were replaced with 18” Excel aluminum rims and super skinny Bridgestone BT39ss tires were used. I made some rear wheel discs from ABS sheet to help reduce drag. The fuel tank was made from sheet aluminum and houses the nitrous bottle inside it as there is nowhere else on the bike to put it!
The seat is from a 1981 Yamaha TZ125, the fairing is from a 1970 Kreidler GP50, and the front fender is a generic landspeed racing fender modified to fit the leading link fork.
The paint was inspired by the 80’s Kevin Schwantz “Lucky Strike” livery, but modified to use my logo instead.
• Does the bike have a nickname?
The bike has many nicknames, but lately I’ve been calling it “the Speedy Seagull.”
• Can you tell us what it’s like to ride this bike?
This bike is extremely light (135lbs!), so it’s predictably twitchy. It’s very compact, but not uncomfortable for short rides. The turning radius is terrible due to the large fender and skinny fairing, but at Bonneville that doesn’t matter. The bike is geared very tall, so acceleration is slow, but the bike builds a lot of its power from 7k rpm and up. At Bonneville it doesn’t have enough power naturally to pull 4th gear, so that’s when nitrous gets involved! After hitting that button, the bike changes tone completely and pulls harder than ever!
• What class did the bike run in, and what was the top speed?
• Was there anything done during this build that you are particularly proud of?
I can’t think of one thing that stands out above the rest. There are so many details and things that mean a lot to me because of what it took to make them come to life. I’m proud of the entire bike for enduring the punishment I gave it and bringing home a record on its first outing. I couldn’t be happier!
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