You did check the spark across a known good spark plug, or from the wire itself to ground didn't you? Otherwise, do that as your first step. If isn't the spark plug, and because it can't be kill-wire circuit if it gives a yellow spark, it has generated as a weak spark due to either a primary or secondary ignition circuit fault. However many things could cause such a fault. If it does not have breaker-points, and you've set the clearance between ignition module pickup and flywheel with a visiting card, you seem to be left with earthing faults, weak flywheel magnet, or a bad module.
Last edited by grumpy; 21/11/09 04:43 AM. Reason: clarification
