Won't start, no spark, no ideas why…

[balooba]

Hello everybody!

I'm totally out of ideas why my 250 cc Kubota engine won't start.
Everything was okay but the next day the engine would not start. No spark.

The sparkplug seems to be okay, I replaced the ignition coil - and the wires - to new one. I disconnected the kill wire... Nothing, no spark. I just can't find the reason.

Is there any ideas, some checklist to go thru systematically, or something...
Only special thing I did the before the engine stopped to run was that I removed, and put back, the battery.

All ideas welcome! Thank you in advance!

 

[Scrubcadet10]

Flip the coil over and see if you get spark...
Also, are the magnets on the flywheel pulling?

 

[balooba]

Flip the coil over and see if you get spark...
Also, are the magnets on the flywheel pulling?

Okay, that's a fresh idea. I'll try the ”reverse coil”, thanks.
Yes, the magnets are strong and healthy.

This case is a total mystery for me. I just don't get it…
I think I'll inspect the kill-wire one more time, too. Could it be somehow that it has to be connected somewhere for the ignition?

 

[bertsmobile1]

NO
The kill wire is a ground wire
It grounds the coil to prevent current building up in the coil
You remove it to check to see if the no spark problem is in the wiring or the magneto
Inside the magneto is a Hall Effect trigger which basically replaced the old points.
These are polarity sensitive .
Some trip when the generated voltage gets to a certain + voltage while others trip when the coil gets to a particular - voltage
When you fit the coil, usually it has an indication which way it goes
If for instance your magnets generate a pulse that goes 0V to +200V to 0V to -200V and back to 0 V again as the magnets pass and your trigger chip is set to a - trip voltage then by the time the circuit trips there is no flux left to generate a spark because the magnets have all but passed .

Usually Hall effect magnetos are designed to go negative then positive so stray ripples from the alternator does not trip the coil
mechanical points and capacitor discharge ignitions usually go positive then negative by reversing the polarity of the magnets .