Torques Moto’s 1100-powered GSX-R750 Slingshot…
Legend has it, the original Suzuki GSX-R “7/11” (GSX-R1100 motor shoehorned into a GSX-R750 frame) was featured in the September 1992 issue of Performance Bikes. The bike was said to outperform a new Kawasaki ZZ-R1100 for a fraction of the cost, and over the years, the project has inspired hundreds of shed-builders to build Gixxer 7/11 machines of their own.
“The combination of the monster torque of a GSX-R1100 and the light weight and short(er) wheelbase of a 750 chassis results in a bike which ‘Has enough torque to pull a Brontosaurus out of quicksand’ and ‘Leaps out of your hands coming out of corners without even being asked…’” –Old Skool Suzuki
Enter our new friend Diggory “Digs” Rush (@torques_moto), a London-based design engineer and university lecturer who grew up around his old man’s BSA and Kawasaki café racers and began building bikes of his own at the tender age of 13.
Fast forward to 2023, and he’s just finished the 1990 GSX-R 7/11 you see here, dubbed “Pick ‘N’ Gixx” since nearly every part of the bike was acquired in pick-n-go fashion from eBay, Facebook Marketplace, the local autojumble, or from members of the oldskoolsuzuki.info forum, who were highly supportive of the project:
“A lot of very talented engineers, racers, and turbo nutcases willing to answer my questions on jet sizes, carb rubbers, and general compatibility.”
Digs envisioned an 80s endurance racer aesthetic with some wild design touches and modern performance parts, finding inspiration in bikes like Haxch Moto’s Slabside and the creations of Sticky’s Speed Shop:
“I’ve always loved the look of the endurance racers of the late 80s, but I’ve never had a bike with decent brakes and I’ve always wanted that classic twin headlight racer look. So I knew I was going to do a restomod with the eventual plan of a fuel injection conversion…”
Digs has learned a hell of a lot since he was 13, and he brought his full design and engineering expertise to the build. He 3D-scanned parts at University College London, utilized software such as Solidworks and Cinema 4D to build the bike virtually, ran Finite Element Analysis (FEA) and motion studies, and turned out an arsenal of billet aluminum parts on his 1920s IXL line-shaft lathe and small bench-top mill, working out of a council garage.
The result is one of the most striking customs we had the pleasure of seeing at the recent Bike Shed London Show, and it has the performance to back it up: 135 hp, 77.5 ft-lb, and a dry weight of 388 pounds. The suspension setup is highly adjustable, including various plates to alter the rear suspension linkage ratio. Says Digs of the ride:
“Aggressive and unforgiving, but predictable. Ultimately it’s very adjustable with 150mm ride height adjustment in the rear alone to make it properly nosey…”
Below, we talk to Digs for the full story on this stunning Gixxer 7/11, featuring photos straight from Bike Shed London 2023.
GSX-R 7/11 Restomod: Builder Interview
• Please tell us a bit about yourself, your history with motorcycles, and your workshop.
So I’m a 27-year-old design engineer and university lecturer. Most of my work is digital and I never really see it once it is out of Solidworks. I’ve always been into bikes and grew up around my dad’s café racers, notably a BSA A65 Lightning and a Kawasaki Z650 which he rode back from Berlin.
I started building bikes when I was 13, a BSA Bantam D1 and a KX250, both of which are still unfinished in my attic. The Gixxer is my first finished build!
I started building this bike on the street when I lived in a studio flat in central London. We had an outdoor area where the washing machine was; that was where I used to keep my swingarm, brake calipers, and what not. When I bought new bits I used to strap them to my SV650 and ride into UCL, where I was working at the time, and 3D scan them with Creaform scanner.
My workshop now is a council garage that I run a 25m extension lead to from the neighbor’s garden. I was given the keys to the garage by an old lady who went to hospital and never came back in mid 2022 and the council no longer rent them out as they’re due for demolition.
Since having the garage I’ve bought a 1920s IXL line-shaft lathe and a small bench top mill and a TIG welder. The lathe and mill were broken when I got them, but I fixed them up and they work well enough for me. That’s where I’ve made all my suspension mounts, wheel spacers, etc.
• What’s the make, model, and year of the donor bike?
So there was never a donor bike, but I bought a frame off a guy on eBay who was building up a restomod 7/11. He had a few other bits he sold me as well: loom and set of bar controls.
• Why was this bike built?
Entirely a personal build. I had a go on a GSX-R750WP [1993 / Water-Cooled] and loved it so much I bought myself one as a project. But the output shaft thread was damaged and the loom was ruined, so the initial plan was to swap the swingarm and front end onto an earlier Slingshot frame and use the much lighter oil-cooled engine. But this never happened as I ended up just fixing the WP, so the oil-cooler frame became my personal project, diving into kinematics and making a bike with all the parts I wanted with the goal of having a lightweight Slingshot that I could adjust to suit whatever I was riding: track, fast roads, or twisty short circuits.
The WP is the next project; plan is to make something a bit less precious so I can get better on track. It’s taken a backseat while this one has been in the works, but now I’m too precious to want to rag it on track until I’m a bit better!
• What was the design concept and what influenced the build?
So I’ve always loved the look of the endurance racers of the late 80s , but I’ve never had a bike with decent brakes and I’ve always wanted that classic twin headlight racer look. So I knew I was going to do a restomod with the eventual plan of a fuel injection conversion, as I love doing something complicated once but can’t stand balancing carbs.
In terms of specific bike influences, there were also a few bikes that I saw really made me want to try and push the build to the next level. The two standout bikes were the Widow Licker by Sticky’s Speed Shop, Haxch Moto’s Slabside, but Paul from Ziggy Moto also really inspired me to try building the whole bike virtually, which I did.
I think that’s the big reason behind getting the graphics to look right. I spent so long trying different things at a very low cost. I also learnt how to use Cinema 4D, which is the software he mostly uses instead of my daily Solidworks, Rhino 3D, etc. It was a challenge in itself!
• What custom work was done to the bike?
So I redesigned all the suspension mounting points and machined them up on my mill out of 6082 ally billet; I also made up all the linkage components. I machined a new crush tube for the swingarm, machined 12.4mm off the sprocket carrier, machined a new brake caliper hanger, machined the R1M calipers, modified the WP mudguard.
New subframe, new tank mounts. Modified top yoke (soon to make another one), SLA printed speedo mount, Daytona Velma 80 15k tach and speedo, 19-row oil cooler, 8AN lines, rear-set mounts for the Gilles VCR rear sets off an Aprilia Tuono, rear single race seat/fairing.
Motogadget bullet rear indicators, machined my own indicators to clamp on the stock rubbers from a set of cheap bar end indicators, aftermarket dual tail light/brake light. SV650 master cylinder, Showa BFRC shock off a 2018 GSX-R1000R, designed a new set of graphics fitted by Kent Wraps, radial clutch master, braided Hel lines, Lucas lithium battery, 750cdi for ignition advance, BST38 carbs, quick-action throttle.
Also did a load of FEA [Finite Element Analysis] and motion studies, but that’s all just the beginning of the testing — need to put them into the real world now and see if my safety factors are big enough!
• Does the bike have a nickname?
So it’s called the Pick N’ Gixx, as it never started out as a bike; it really was just parts from autojumbles, eBay, Facebook Marketplace, and the oldskoolsuzuki forums. Nothing is the absolute top tier part, but they are all performance parts selected for specific reasons. Could I feel the difference between a set of Z04 pads in R1M calipers over M50’s? I doubt it, not at my skill level, and certainly not anytime soon.
• Any idea of horsepower, weight, and/or performance numbers?
135hp, 105nm, 176kg dry. Still interested to find the wet weight and drag coefficient.
• Can you tell us what it’s like to ride this bike?
Aggressive and unforgiving, but predictable. Ultimately it’s very adjustable with 150mm ride height adjustment in the rear alone to make it properly nosey. Also a load of different linkage plates that can be swapped in to change the ratio — currently it’s setup for 2-2.28, which is very close to a GSX-R1000 K5. Unfortunately though, I’m really not capable enough of pushing it anywhere near its limits!
Big issue at the moment is the exhaust. I’m waiting on a set of titanium headers off a K1 GSX-R1000 as my 750 headers are sitting too low and the link pipe isn’t helping my ground clearance at all. Back when I had the 750 engine in, it could lean over really nicely. But, that will be sorted in the next couple of weeks. Just got to get a dent out by shoving them in the freezer.
• Was there anything done during this build that you are particularly proud of?
The rear suspension linkage, particularly the adjustable rear shock mount. It’s my first big project and diving into kinematics and load cases of motorcycle rear suspension was a pretty steep learning curve. I read a lot of papers, spammed a load of people on LinkedIn who kindly helped me fill in the gaps in my understanding.
• Is there anyone you’d like to thank?
Oh, hands down the oldskoolsuzuki.info forum — a lot of very talented engineers, racers, and turbo nutcases willing to answer my questions on jet sizes, carb rubbers, and general compatibility.