KZ440 LTD Build

Since your bike has points, have you checked them?  

Test the ignition coil first for it being in the roughly right range for resistance on the primary and seconday winding. Old coils can fail when they get hot, for sure. I'm using a replacement coil because I have to. I think replacement coils are garbage btw. Maybe they work but for how long - who knows. Did you check for battery voltage though? 12.6+ volts is healthy. When you start the bike, the starter motor's draw will drop this a lot at the input to the coil. but it should immediately come back up when the bike starts. It needs a lot of voltage to collapse the EM field and produce a spark. If you're testing this, check also that your points spring is isolated from the bike's ground, and that the input to the coil is likewise not shorting to ground. 
Regarding aftermarket parts in general: they are what will eventually terminate these bikes. Everything from fake spark plugs to coils that don't work, etc. 

Michi wrote:

Test the ignition coil first for it being in the roughly right range for resistance on the primary and seconday winding. Old coils can fail when they get hot, for sure. I'm using a replacement coil because I have to. I think replacement coils are garbage btw. Maybe they work but for how long - who knows. Did you check for battery voltage though? 12.6+ volts is healthy. When you start the bike, the starter motor's draw will drop this a lot (approx 10.0v) at the input to the coil. but it should immediately come back up when the bike starts. It needs a lot of voltage to collapse the EM field and produce a spark (the EM field is collapsed by breaking the ground - the input voltage will simply determine the HT voltage as a ratio). If you're testing this, check also that your points spring is isolated from the bike's ground, and that the input to the coil is likewise not shorting to ground. 
Regarding aftermarket parts in general: they are what will eventually terminate these bikes. Everything from fake spark plugs to coils that don't work, etc. 

To be honest I think the exact opposite, in many cases "aftermarket" parts are what are keeping these bikes on the road with many OEM parts now obsolete. There is however "aftermarket" and then there is "oriental aftermarket" (and not even all of that is garbage, it's just a lottery as to which is)

Wookie58 wrote:

(the EM field is collapsed by breaking the ground - the input voltage will simply determine the HT voltage as a ratio). 

Yes I know - the point I was trying to urge was making sure there is enough primary voltage there so that the multiplied-up voltage at the spark plug is sufficient to create a good spark.

Hi all,

Thanks for the responses. I did verify the dwell gap on the points and verify that the spring has no continuity with ground when it’s not touching the contact breaker points. The contact itself is certainly worn but not bad enough to affect anything I think. 

The preinstalled Nippon Denso 029700 ignition coil (from a GS750?) has resistances across the coils that are in the expected range when cold. The battery is fine as well.