Pictured before and after I completed a total restoration of this numbers matching Bultaco MK6 M101 175cc Pursang.
Pursang M101 Before 
Pursang M101 After 
Pursang M101 After 
Model 101 175cc Pursang 
Model 101 Pursang 175 
Polished engine 
The best story of the Bultaco Pursang was starred by a barely 20-year-old pilot, at the controls of a near-production Mk6. In the first round of the World Championship of motocross in 1973, an unknown Jim Pomeroy debuted with a spectacular victory over reigning champions.
Bultacos (or “Buls” as they were affectionately known) a beauty all their own. They had shapely, extremely thin fiberglass gas tanks-so thin that the head fins stuck out on either side. They also had superb handling. In corners, their ability to either pivot in soft or hard soil, or to rail berms with equal aplomb, made them extremely accommodating for a range of riding styles. Despite the limitations of suspension travel they managed to be relatively stable (for the period). Having great torque allowed the rider to rely on brute power to get them out of corners a gear high, thus requiring less shifting. In 1974 Bultacos were right foot shift, making the change to left side in 1975. They employed an interesting design element in their engines that significantly influenced the nature of the machine’s power delivery. Cylinders were offset, positioned slightly forward above the crank. The theory was that on the power stroke, the piston rod was pushing more straight down on the crank-as opposed to being at an angle. The concept was a basic aspect of physics; more inertia was transferred to the crank. Whether or not it really worked was never substantiated-other than the fact that Bultacos had enormous pull and low-end torque.