The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: delboy on 21.03. 2021 21:17
-
can somebody please tell me if the ht leads on my a7 ss magneto have to go to a specific side of the engine , or can they just be connected anyway round , at the moment the upper ht lead is connected to the off side cylinder ....thanks
-
I believe that the system is a wasted spark one so each plug fires on both the ignition stroke and at the end of the exhaust stroke, so should work either way, but don't take that as gospel or words of wisdom of any sort. I'm probably wrong, my wife tells me I usually am.
-
thanks Minto i will wait for some more replies
-
Your wife is correct, you are wrong again.😁 Remove a pick up lead from mag and rotate engine until brass appears, that lead fires whichever cylinder is on compression stroke.
-
God, I hate it when she's right. Lol.
I'll get me coat!
-
Yup, you need to set things up correctly - there is no wasted spark, they're alternate sparks one at a time. So the mag has to be set to fire the piston that's on compression. Some people prefer front pick-up to the left, others to the right. I set my bikes 'rear to the right' every time so I don't have to think about what's what on any particular machine.
To save having to peer into the gloom looking for the brass bit through a pick-up hole, the rear (gearbox side) pick-up on the mag is fired by the lower lobe on the camring, the engine side one by the upper lobe.
But even if you muddle up the pistons, swapping the plug leads when it won't start should solve things.