Bultaco ASTRO M-163

Technical Details

Year Built : 1976 Engine : 250 cc Two-stroke single Transmission : 5-Speed Electrics : Motoplat CDI flywheel magneto Notable Features : The Astro displayed here is somewhat of an amalgamation, It is listed as a Model 163 by virtue of its motor, Frame / chassis is actually from a 250 cc Model 195, The cycle's M-163 motor was one from Mike Kidd's early days, The Kidd cylinder has interesting porting but an M-192 Pursang top end was used instead, This build was accomplished as a spare-time project over a few years, The goal was to achieve a smooth-running high-speed motorcycle capable of winning on tracks with half-mile lengths or greater, Porting with more area and longer timing was carried out along with head & squish band modifications to eliminate possible detonation, Naturally the inlet manifold was included in the port work and its ID was matched to a Mikuni VM carburetor, The Mikuni replaced the OEM Bing carb and jetting was simplified due to Mikuni's superior availability of " brass ", Hugh's Bultaco supplied the new exhaust pipe, As stated above the CDI magneto is a Motoplat and it came from the same M-192 MX'er cannibalized for its cylinder, head, and related studs & hardware ( all Buls should have the 192 head bolt arrangement ), To damp motor vibration and minimize ringing during wide-open-throttle conditions the often discarded head-to-frame brackets were retained, Work relating to the bike's running gear was performed : Wheels were built using Buchanan's SS spoke sets, The rear wheel received a wider WM-3 Akront " Green Label " alloy rim, Storz sprocket adapters with aluminum two-prong knock-offs were stronger and more reliable than the OE items, Frank's fork tubes made the front end work as perfectly as the new rear shocks from Progressive Suspension, Tires are a Goodyear and Dunlop combo, Frame painting was courtesy of Lowrie Chevrolet in Fort Worth, Texas while the fuel tank & tail section were left with their factory-original paint " just because " both remain undamaged and....original ! Tuning & testing was carried out using various Track Tek fuels and higher octane blends proved to be the ticket, Finally the work paid-off and the Bul was raced very successfully at the Devil's Bowl Speedway in Mesquite, Texas.

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