Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/127740
(Left) Veteran scrambler Peter Remington puts one of the 'dope burners' through its paces. Remington rode such a machine at the Scottish Pre'65 motocross championships In 1995. According to Remington, there Is no comparison between the modified machine and its stock counterpart. without any radical tuning, and the power is available right through the range, not just at the top end. These are very ridable bikes. Methanol is a muchmisunderstood fuel. Everyone thinks that the motors will be very fiery, but this just isn't true. "You do need to run a high compression ratio - I reckon 13.5:1 is right for a scrambler - compared to 11.4:1 for gasoline," Walker said. "And you have to run much richer jetting - you get through a lot of fuel running 'dope.' You can also vary the ignition timing over a greater range than with gasoline, but the real big bonus - apart from the power boost - is much cooler running. The engines run so coolon the BSAs that I sometimes machine most of the £inning off of the barrel." Walker continued, "Methanol is slower burning than gasoline, and I modify the cylinder head to take two plugs and run twin-spark ignition. Twin plugs with gasoline don't show much benefit, but the twin flame-front pays dividends on methanol." So how much power are we talking here? "A well put-together 500 BSA might produce 35 brake horsepower on gasoline," Walker said. "I know we are talking 45-50 brake horsepower for methanol. I tested a 350 motor, that I had built for grass-track, on a dyno and it knocked out 52 brake horsepower when peaking at 9000 rpm." Because of the wide spread of power, Walker converts the gearbox to a three-speed, ditching the normal first gear and machining a new cam plate. More machining is employed to give the gearbox main shaft an outrigger bearing which solves an old BSA bugbear. The clutch is given an extra plate to beef it up, and increased operating leverage to give a light feel. The baseplate' at the bottom of the barrel is there because Walker has been experimenting with an italian-made. piston that has the wrist pin at a different height than standard. The stroke remains the standard 90mm for 440cc and 500cc, and 70mm for 250cc and 350cc. Ignition is by either Motoplat, Boyer or Interspan. So into which chassis is our now fire-breathing motor fitted? Nothing more exciting than a standard BSA. "Anything, as long as it is not a GP frame," Walker said. "They were a dis- "Basically, it is everything that a standard Victor isn't," Remington said. "It is very rapid and it definitely handles. The engine'is powerful but totally controllable, and it is so easy to powerslide or drift across a loose bend just on the throttle. And amazingly, there is little vibration." Walker gives the frame mods a lot of credit for this. "I haven't been on a 'dope-burner' before, but I am very impressed with this," Remington said. "I reckon it will see the 400 CZ off quite easily. I wondered if three would be enough, but the spread of power is just amazing - I seriously think a two-speed transmission would 'be enough with this motor." (Right) The builder: Alan Walker poaes with one of his conversions. Waiker's bikes have proven so successful that they are . being considered for exclusion from English classic competition. aster. Right from the CIS of 1962, all the other BSAs used the same frame. Getting the handling right is as important as the engine, and I know just what to do. "The frame is standard, but I fit my own swing arm, which is actually a copy of a 650cc BSA fitted with elongated wheel-spindle slots so that the wheelbase can be varied for different tracks," Walker said. "And I fit a strengthening, additional top tube with a built-in head stay. This makes for a really rigid chassis that handles. The geoQ1etry is very important to get the steering right, and I know exactly which Marzocchi clamps work. It really doesn't matter which forks you use after that as long as they are set up right." How do they ride? The objects of the test day we had were a couple of full 500s that Walker had screwed together, both running on "dope," for the benefit of a prospective customer - Peter Remington - the grizzled veteran of many a summers' scrambling. Remington had come along with his son Scott. Both ride Classic events, and Peter Remington - a confirmed CZ man - wanted to try th~ BSA as well as give young Scott his first four-stroke ride. Peter Remington, who has ridden just about everything on wheels offroad, gave us the benefit of his experience following a blast on the beast. The two machines' suspension setups were very different - one ran soft, short shocks and soft forks. The other was much stiffer and fitted with 13.5-inch long units. "The bike with the longer, stiffer shocks was the one," Remington said. "It han.dled so much better and steered inch-perfect." The Walker-BSAs are now-on the British scene and are built to order, but because of their initial success rate there is already a black cloud on the horizon as several of the British Classic organizations are threatening to ban methanol burners. But until the methanol machines are banned, the CZ and Metisse set have got a real fight on their hands. And the fact that both Remingtons ended up this year on Walker-built BSAs must mean something. Isn't variety supposed to be the spice of life? Editor's note: Although .the above story provides an entertaining insight into the technology being applied to the British vintage racing scene, sueh a machine would be illegal at an AHRMA-sanctioned motocross or scrambles. AHRMA specifies that "gasoline only" be used at its events in the United States Ridersl mechanics interested in using alcohol should check with whichever sanctioning body they are affiliated with before attempting such a conversion. helps you do all your gift shopping at one time. Your family and friends get aweekly reminder of your thoughtfulness each time Cycle News is delivered to the.ir door. Plus, you don't have to worry about sizes, colors or styles. Cycle News is perfect for everyone. Subscribing is as easy as one phone calL 1·800·831·~~~O 9:00 a.m. - 5:00 pm. ps.T. With 50 issues, they will be thinking of you week after week. Need agift? Send' a subscription of Cycle News.