John from the point of view of running, it doesn't matter a jot if you have tight or slack wire advance. But for an anti clock mag you must have an "L" stamped on your cam plate, as seen here on my spare BSA/Triumph and Enfield mags. As per Rik's mag the clockwise mag needs an "R" cam plate.

I guess the Left and Right denotes what side of the plate the points are actually opening on. Ron

email (option): ronpier@talk21.com

Magnetos built from pieces can be a problem, i have come across 3 different cam plate for these mags. First thing i do with an unknown mag is to check the magnetic flux timing. If right is when you turn the mag in its correct direction you can feel the magnetic flux. The points should just break on full advance just after full magnetic flux, dosnt make any differance if its slack wire or tight wire advance for this check as long as you have it on full advance. If you have got this then you are on the way to having a good magneto. But coil and condenser are not checked in this test.