Re: JD 210 quit wont restart
To answer your question - you saw spark, so spark is good? Maybe - maybe not.
You can have a weak spark that you see when you test it, but under compression it is not enough to run.
Things that can weaken the spark:
1. carbon build up on plug - the carbon allows the spark to travel to ground rather than jump the gap (try a new plug)
2. weak ground (try taking a wire from the coil body to the neg battery terminal). I chased this issue on my 317 for quite awhile - replaced points, cap etc - all for a corroded ground wire.
3. weak voltage to coil (can take a wire from coil to pos battery)
4. bad capacitor (try a new one). A bad cap will often give you spark, but it is weak and short in duration.
5. Bad sparkplug wire. High resistance eats the spark or cracks allow leakage to ground.
6. Bad coil
7. Points? Usually point issues result in no spark or bad timing
...and a bad seat switch would typically mean no spark, but is could reduce the voltage to the coil. Jumping a wire from the coil to bat pos would rule this out.