Spark should be the same always. In some conditions you may see weak spark that picks up with rpm.
The spark should be blue, jump a wide gap like lightning, while giving off a 'snap'. If it's orange/yellow, maybe a bit fat, and sounds more like a tiny 'click', it's weak.
If you see weak spark, check the other wire too. It might help decide if it's the wire or the coil, etc..
Voltage to the coil is important, worth checking if the spark is weak. Then there's the coil relay mod, and the pickup coil mod.
I'm assuming the charge and battery voltage is good at startup?