They were called sandy bike spares, I think it was to do with the way they were configured , the exup valve is a good piece of kit most bikes have something like it now, if you put a straight through exhaust it has to be set up to give the torque and top end, if its not right you will get flat spots or hesitation. someone will come along and explain better than me , try stripping the exup valve ,watch the bolts they snap very easy, disconnect the cables at the valve end , the turn the ignition on and see if they move that will tell you if the servo is working, I have my old valve which was working Ok . Pm me we can work a price, have a look at pats site there's a step by step guide on there
the night i was born, lord the moon stood a fire red., my poor mother her crying,
she said the gypsy was right, and she fell right dead
she said the gypsy was right, and she fell right dead