Spirit of ’78: 1230cc Suzuki GS750E Restomod

Big-Bore 1100EFE-Powered Dream Machine from Jon Lilley… 

In the animal kingdom, young animals form a strong attachment to the first moving object they see, usually a parent — a process called “imprinting.” In the motorcycle world, a similar form of imprinting seems to take place between aspiring young motorcyclists and certain machines of their youth. For London-based shed-builder Jon Lilley (@Diesel_Jon), a late 70s Suzuki GS750 made an impression he would carry into adulthood.

“When I was a kid, a guy who lived round the corner rode a GS750. At the time, it was the biggest, loudest, fastest motorcycle I had ever seen. I decided this was the epitome of motorcycle cool and one day I would own one.”

Fast forward some 40 years, and Jon realized his boyhood dream when he picked up a 1978 GS750E. However, he soon realized it wasn’t quite the world-beater he remembered. No matter, the shed-builder would make it so.

“I wasn’t going to rebuild it standard: I was going to build the fire-breathing monster of a bike I remembered.”

This has been Jon’s most comprehensive build to date, a frame-up rebuild that includes a serious engine transplant. Out went the old 750 lump. In its place, a mighty Suzuki 1100EFE engine bought from an ex-racer, complete with 1230cc pistons, Teflon gudgeon pin buttons, tool steel head bolts, high-pressure oil pump gears, 10-row oil cooler, undercut first and second gears, Mikuni carbs, and more. 

“I wanted the bike to look as factory as possible, for that ‘sleeper’ look. So I sourced most parts from other Suzukis, rather than buying new aftermarket items.”

The frame itself was braced, blasted, and powder-coated, and the bike is running 1999 Kawasaki ZX9R forks, NOS Marzocchi Strada rear shocks, and a period Spondon swingarm — trick! The front brakes boast Nissin 6-pot calipers, and the exhaust is a one-off system from Exhaust Craft. The mods go on and on… Jon’s included a full build sheet below.

So how does “The Spirit of ’78” perform? Jon says that, despite all the mods, this 1230cc GS sleeper / restomod is quite well-behaved.

“Anyone could jump on and ride it anywhere… It corners well considering it’s set up for straight lines. The mid-range power and torque are insane though.”

Jon’s done a 7.48-second run at the Malle Mile, though he thinks the bike could go sub 7 seconds on a proper drag strip. We absolutely love this fire-breathing GS and the story behind it. Jon, bravo for building this dream bike and sharing it with the rest of us.

Below is our full in-depth interview with Jon about the build, including more photos and a full build sheet.

Suzuki GS750 Restomod: Builder Interview

• Please tell us a bit about yourself, your history with motorcycles, and your workshop.

My name is Jon Lilley. My day job is in advertising and design, so I guess you’d call me an amateur shed builder. I began riding in the mid-80s and have worked on all my own bikes ever since: initially because I had to, but it became a hobby that just got out of hand. I’ve done a lot of restoring, rebuilding, and modifying but this was the first time I’d done an engine transplant.

• What’s the make, model, and year of the donor bike?

1978 Suzuki GS750E.

• Why was this bike built?

I just wanted to do something more ambitious than I’d attempted before. Buying a bunch of parts that were never meant to go together and building a motorcycle out of them: how hard can it be?

• What was the design concept and what influenced the build?

When I was a kid, a guy who lived round the corner rode a GS750. At the time, it was the biggest, loudest, fastest motorcycle I had ever seen. I decided this was the epitome of motorcycle cool and one day I would own one. A lot happened in motorcycle technology in the 80s and by the time I was old enough to ride, I realised the old GS was a slow, heavy, poor handling machine. It was only many years later I decided to revisit that dream and buy one. But I wasn’t going to rebuild it standard: I was going to build the fire-breathing monster of a bike I remembered.

• What custom work was done to the bike?

It’s been a complete frame-up build. The only original parts are the frame, tank, headlight, taillight, bodywork, ignition switch, and some switchgear.

I wanted to retain the bike’s original silhouette so that meant RWU forks and retaining the twin shocks. I sourced the forks and yokes from a ZX9R C2, as they were the thickest RWU stanchions I could find at the time. I managed to get some NOS Marzocchi shocks from Spain (they even came in the original box), and was really lucky to pick up a period Spondon swingarm from an ex-racer.

My engine of choice was always the mighty 1100EFE, and I was able to obtain an engine that already had a 1230cc conversion from another ex-racer. It also had work done to the gearbox and a beefed-up clutch. I couldn’t afford the modified head at the time, so I fitted a standard head and cams.

The exhaust had to be fabricated as I wanted something that looked like it was from the 70s, however I couldn’t buy anything off the shelf because the EFE engine was sitting further forward than the original 750 lump and at a different angle. I also wanted a flat collector box due to the bike running so low.

I wanted the bike to look as factory as possible, for that “sleeper” look. So I sourced most parts from other Suzukis, rather than buying new aftermarket items. For example, the clocks and clock mount are from a 400 Bandit, as they had the pod look and fitted nicely around the original ignition switch. And I used Hayabusa footrests and foot controls because they had the rubber footrests, which suited the style of the bike.

The frame bracing behind the air filters meant that the battery box had to come out and be re-made for a smaller lithium battery located on its end. I also had to relocate all the electrical gubbins that had been mounted on it.

I also moved the taillight back a couple of inches so it sat inside the tailpiece, which made the rear end a bit tidier. A lot of time was spent getting the small details right.

Chassis and running gear
Frame braced, sand-basted and powder-coated
Suzuki Hayabusa footrest hangers, pegs and controls
1999 ZX9R forks and yokes

Kawasaki ZX9R front wheel
One-off steering stem
New Renthal bar clamps
New headlamp brackets

Period Spondon swingarm
‘New old stock’ Marzocchi Strada rear shocks.
GSXR600 rear wheel (5.5in) with machined down Hayabusa sprocket carrier
Offset front sprocket
DID ZVMX 530 chain

Engine and drivetrain
Suzuki 1100EFE engine
1230cc Wiseco pistons, Teflon gudgeon pin buttons and tool steel head bolts.
Undercut first and second gears
High-pressure oil pump gears
Orient express clutch springs and billet backplate
Manual camchain tensioner
Mikuni BST36 carburettors (Bandit 1200) rejetted and rebuilt
K&N twin oval air filters
New one-off exhaust system by Exhaust Craft
10-row ‘Mocal’ style oil cooler and braided lines
Braided external oil lines and breather hose

Brakes
Front: Nissin 6-pot calipers, new discs, HEL braided brake lines and Suzuki GSXR1000K4 master cylinder.
Rear: Suzuki Hayabusa master cylinder, disc, caliper, and new HEL braided brake line.

Bodywork
On-off front mudguard made by The Tank Shop, Aberdeen
Guiliari period seat recovered by Viking Motorcycle Seats
Resprayed tank, side panels and tail piece by Dream Machine
New tank badges and side panel badges
Tailpiece and mount modified and rear light ‘Frenched’ in

• Does the bike have a nickname?

The Spirit of ‘78.

• Any idea of horsepower, weight, and/or performance numbers?

It’s only putting out about 110bhp at the rear wheel. I think this is down to still using the standard head and cams. I ran an 1/8th mile in 7.48 at the Malle Mile a couple of years ago, I’m sure on a proper track it would easily go sub-7 seconds.

• Can you tell us what it’s like to ride this bike?

It doesn’t feel like you’re riding wildly modified bike. Anyone could jump on and ride it anywhere; it’s very well behaved. It corners well considering it’s set up for straight lines. The mid-range power and torque are insane though.

 

• Was there anything done during this build that you are particularly proud of?

The original top yoke from the ZX9R had no way of mounting the ignition or clocks. In keeping with the “factory look” I was after, I asked Gary, my engineer, if we could cut the front half off an EFE yoke and weld it to the ZX9R one. He was skeptical that it would work but it turned out brilliantly.

I’m really happy with the exhaust. It follows the lines of the frame perfectly, and I love the way it snakes out from under the sump. There’s no link pipe so it looks really clean.

• Is there anyone you’d like to thank?

Gary at Mid Engineering, who did all the welding, fabricated some parts and put up with many stupid questions. (www.midengineering.co.uk)
Maldon Shoot Blasting and Powder Coating, who did amazing work particularly on the wheels. (ctc-powder-coating.co.uk)
Dave at Exhaust Craft in Whitehaven for the lovely pipework (www.exhaustcraft.co.uk)
The guys at OldSkoolSuzuki.org, always a great source of information and advice. (oldskoolsuzuki.info)

Follow the Builder

Instagram: @Diesel_Jon
Photos by: [email protected]