It's the curve marked AAU. (automatic advance unit)Wow, there's a fair bit of variation at tickover going on between those ignition systems. 1 to 16 degrees of advance. May explain why some bikes start easier than others. Does anyone have the factory points / advance unit curve?
There’s a massive difference all the way through the rev range !Wow, there's a fair bit of variation at tickover going on between those ignition systems. 1 to 16 degrees of advance. May explain why some bikes start easier than others. Does anyone have the factory points / advance unit curve?
With my bike, I run methanol with 34 degrees ignition advance. One thing I really avoid is moving the trigger of my Boyer. Jetting the carbs is tedious.The specified ignition advance should only apply when compression ratio is standard and you are using specified fuel and jets. If you change compression ratio, fuel type or ignition advance, you need to rejet to suit the change. For a road bike, it might only involve raising or lowering the needles one notch - the main jets are should be rich enough to cope with a slight increase in ignition advance.
I think if you get the timing ‘out of range’ you’ll see a drop off that drops off exponentially the further you move away.
But on the dyno, with Triumph twins, triples, Nourishes and Nortons, I have persoanly found that ‘the range’ is a good few degrees. Meaning that a couple of degrees either side of ‘nominal’ just doesn’t show up on the dyno. But, of course, you do have to know what ‘nominal’ is for your set up.
My other controversial point about timing is the randomness of the ign curves. Depending on which system you have, you can be miles ‘out’ of where you thought you’d be after setting the timing ‘correctly’.