We’ve met Mark Walker before. In Issue 12 we got acquainted with his humungous creation, Big Ned. Now, here’s one he prepared earlier…
What was originally known as the MW Special came into being because Mark had basically exhausted the scope for modifying existing designs, mainly Triumphs, for drag racing. Back when Castlereagh drag strip was operating in Sydney’s north west, Mark and his Triumphs were a regular feature, and always very competitive. Finding the limits of the venerable Triumph parallel twin he chose a familiar route – fit two engines, but that came with a weight penalty which offset the power gain. His solution was to start from scratch to build a complete bike that weighed no more than 400 pounds (181 kg).
Mark admits to be influenced by the engineering precision he saw in a Bugatti engine that a friend had restored. “When I looked at the Bugatti engine I thought, if they can make their engines out of solid blocks of alloy and turn crankshafts out of solid blocks, that’s what I’ll do.” The design he sketched sounds fairly normal – a 90-degree v-twin with double overhead camshafts and four valves per cylinder. But remember, this was 1975, and apart from the magnetos, forged pistons, valves and chains, he did all the engineering and machining himself. Oh yes, and the capacity was 1,000 cc per cylinder, just about the biggest single ever built, at least in Australia.
He started at the top, with the cylinder heads and cam boxes. The latter are one-piece with the cams running in roller bearings. The cams he turned from 50 mm solid bar, but the final grinding was done at Waggott Engineering. Each valve is fed by its own injector, with its own exhaust port, and Mark made the injectors too, along with the metering unit. He admits that getting the units to work correctly initially eluded him, so he sought the help of McGee Injection in Sydney who were vastly experienced with speedway cars. The valves were speedway influenced as well; from the successful VW engined midgets that were the big thing at the time, 44 mm inlet and 40 mm exhaust, with buckets sourced from a Jaguar engine. Twin Mitsubishi magnetos, as used on speedway Jawas, fired the plot through single spark plugs. The cams were turned by a double row chain with a tensioner that Mark made using a Teflon running wheel. In between the head and the crankcase sat an iron barrel, turned from solid, clamped down by six studs from a VW engine. The bottom end bearings were plain, with lubrication coming from a modified Honda CB750 pump driven by toothed belt from the rear of the English Puma clutch. Of the all-up weight of 181 kg, the engine itself accounts for 50 kg.
If all this sounds like it’s in the past tense, it’s because it is. Because this was the machine in its original guise, and as with all Mark’s projects, they constantly evolve. In this case, the evolution has been dictated to a large extent by ever-changing rules from ANDRA, the body that controls drag racing.
At the time, in the mid 1970s, Mark had just moved from Sydney with his wife and three young children to Woodstock on the outskirts of Cowra, taking his engineering business with him. His reputation spread quickly though the district and he soon had plenty of work on local speedway cars and bikes. Two tracks, one virtually next door at Woodstock Park and the other at Young, meant there was a constant supply of short circuit solos and sidecars demanding his attention as well. The dragster’s initial outing was in Adelaide, as Mar recalls. “We just loaded it up on the trailer and drove all night from Sydney. Gary Franks rode it.”
But Mark didn’t stay at Woodstock, beginning a peripatetic life that saw him decamp many times until he finally settled in Dorrigo, in the misty mountains inland from Coffs Harbour. Each move meant setting up another workshop, but the MW Special came along for the ride too, and like life itself, was constantly evolving. The chain driving the camshafts proved to be not as bullet-proof as first thought, so a belt-drive system replaced it. The Puma clutch, which had proved OK when used on a British grass track outfit, also withered under the punishment of 300 bhp and was replaced with an America device originally fitted to a Chev. This contains counterweights which throw out to lock the clutch under acceleration, and allow a certain amount of slip otherwise. The ignition was also changed to a Mallory V8 magneto in which six of the eight cylinders are earthed out. At one stage, supercharging was tried.
“ANDRA was always coming up with stuff they didn’t like about the bike”, says Mark, “and to stay in the Top Fuel class (the engine runs on 90% nitro), we had to keep modifying it. They said the chassis was unsafe, so Chris Dowd and I modified the frame to brace the front end. Chris made the new alloy seat pan and we had to put a bigger back tyre in because they said the original one was too narrow. The frame was too short so Chris fixed that by extending the back end. We had to fit disc front brakes too in place of the drum, and they wanted straps around the motor in case it blew up.”
After Gary Franks, another Sydney rider, Peter Munn, took over the controls, and for the final stage of its competitive existence, the pilot was Gary Thomas from Bundaberg, including at the bike’s final run at Roma in Queensland. Mark says, “I know it has done an 8 flat at Willowbank (Ipswich, Queensland). It was my dream to run a 7… the elusive 7 seconds was there for 30 years like gold-fever. The dream when you got to the track was that this was the big one, because you have kept this part of your whole existence at the time alive, by constantly hands-on grooming with thousands of hours of wonderful time, and all the circumstances of life through the journey has a lot of impact of what you do to – things that you are involved on at the time with the machine. Because where you are emotionally at the time, unknowingly has an effect on your work and you’re not seeing things clear because of the fog, so the journey takes longer… and sometimes never reaching the top of the mountain…. even though you have given it the best part of your life… the most valuable asset, your time… and the journey has made me the person I am today. which is what you see.”
Until recently, the MW Special, or as Mark and his partner Lynne call it, “The Green Bike” was housed in a café in Dorrigo, and on one memorable occasion was started up in the main street to an appreciative audience. You can see this at http://www.youtube.com/watch?v=eU6hDoVcUPQ.
In July 2011, the MW Special was transported to the National Motor Racing Museum at Bathurst, where it now resides, and certainly stands out in the motorcycle display that consists mainly of thoroughbred racers. And while this is likely to be the MW Special’s abode for the foreseeable future, it is certainly not the end of the incredible creations coming from Mark’s tiny workshop. Since building the dragster he has completed Big Ned and another totally unique machine he calls the Saltster (see OBA 27 Out & About). And of course, there is the V16 engine he has built, using his own crankcase and crankshaft, topped with 16 cylinders and heads from Victa lawn mowers. Why? Now, you don’t really expect an answer to that, do you?
MW Special – Specifications
Engine: 2000 cc 90-degree V-twin
Bore x stroke: 114 mm x 101 mm
Fuel: Nitro 90% methanol 10%
Fuel method: Two 2-inch injectors per cylinder.
Ignition: Mallory magneto.
Crankshaft: ASAB 8407 Ultra heat-treated steel 35 mm diameter with plain big end bearings, single-row roller main bearings.
Story: Jim Scaysbrook • Photos: Lynne Syrjanen