Strange spark situation

[gwcrim]

My son just picked up a 1986 Honda TRX250R.  A non-running one.  Here's what we know:

1- Plenty of compression.  Top end brand new, never started.
2- New coil and stator, installed by previous owner.  We did not pull the cover and look at the stator but the wires are certainly new.
3- Carb was cleaned and the plug gets wet.
4- It give an intermittent spark.  Sometimes none.  Sometimes right after the crank has stopped moving, we get a spark.  It's a decent spark.

I'm thinking since the coil and stator are new, it's probably the CDI box.  Any input is welcome.

[m in sc]

new doesn't mean good. def worth looking at box though

[SoCal250]

Like Mark said, "new" doesn't always mean good or functioning.
See my write-up about my XT225 troubleshooting. I installed a brand new stator while chasing a no spark issue and after fixing it the issue returned. After chasing my tail for a while assuming it couldn't possibly be the brand new high-end stator I had installed, I discovered the stator had failed after only 16 miles and had a broken wire due to a manufacturing defect.

Have you tested the pulser coil?

I would suggest testing all the ignition components with a DMM, starting with the key main switch, then the coil, then the pulser coil, then the stator. Check resistance values versus the manufacturer spec. Also carefully check the wiring loom sections that pertain to the ignition. If all those pass then your issue is likely the CDI box.

[gwcrim]

The good thing is that this is stone age technology.  Not much to test.  I did quick continuity checks on the coil, CDI, and stator.  They all test good.  Didn't check for exact resistance yet, though.

What strikes me as odd is that the plug will spark after the crank has stopped moving.  Is this unusual or no?

[1976RD400C]

I think if it is sparking without the motor turning that the SCR in the CDI box, that turns on to discharge the capacitor, is failing.

[m in sc]

I agree..def worth trying a new box if available,  or a known good one

[gwcrim]

I took a few minutes to learn how these things work (it's about time.)  I ordered a new CDI box.

Thanks to you all.  And Happy Hollandaise!