MIKE POWELS gears mods page

i just been studying this with, a number of observations.

item 4 no such data exsists for 21 tooth main shaft and 26 free gear

also missing that is on BSA service sheet for gearboxes, IS A 21 X 26 slider gear pare designed for trials these close up the gap between second and top if you modify the a joining to allow the use with a close ratio box setup.

Mike is absolutely correct on going to auto jumbles, i split a 175 d7 engine took a magneto off it so it came out of a road bike and guess what, its been sitting in the shed for more than ten years it has a 22 x 25 output pair the first one's i have ever seen originals so they did exssist.

I had some of these made, great for a 175,

THE REST OF THE INFORMATION ON MIKES PAGE IS EXCELLENT you should pay particular attention to his method of spinning the gears,

I would only add to this by suggesting when assembling to avoid gears jumping out you should before final assembly, check the box spins freely when the cases are locked up with all screws, do not connect to the crank, but stick it in each gear, and you should be able to spin the box, any tightness points to selector flag not in correct position, you may need to grind the v-notch slightly, usually second and top. this is because of BSA tolerances.

Derek