VS800 Intermittent Spark

[tkocher92]

Hello,

I have a 96 Intruder 800 that I purchased in pieces. The previous owner was in the process of turning it into a bobber.

I put everything back together, wired up a turn signal circuit, it seemed to be firing pretty consistently, that is until I took it out for the first ride. I did not insulate the positive terminal properly, and it touched the frame and caused an immediate dead short. There was a little smoke coming from under the seat where all of the electrical components are bunched together.

The battery was incredibly hot, so I replaced it, and since then it's been having a weird issue I've never seen before.

The bike can crank continuously without a spark, and then once you stop cranking it, and press the starter again to begin cranking, the spark shows up. It's almost as if the ignition circuit needs to warm up to begin sparking.

I've eliminated the clip in the signal generator wires. All of the grounds check out. Both coils are doing the exact same thing at the exact same time so I don't believe the coils to be bad, but I did trim some wire from them to be sure.

I'm suspecting it to be the side stand relay. I tried using one from an 07 S50, same issue. If I play with the relay or the diode in that circuit it seems to start sparking, but that could just be coincidence.

Could it be the CDI? I never suspected those would just go in and out, or need to "warm up"

Thank you!

[navigator]

I suspect that since you had a dead short, and smoke under the seat, that you may have melted the insulation on the coil feed wires.
If you peel back the harness covering, you may find the melted zone causing your grief.
Both coils should not fire at the same time.
You may have buggered the CDI, but I can't be sure. You need to isolate the coil wires to be sure they are not shorted to another wire.

[tkocher92]

Awesome, thank you for the quick response! I will begin unwrapping and tracing the harness tomorrow.

Just curious, would I be able to find a short with my multimeter? All of the critical lines are continuous, and display almost zero resistance.

[navigator]

Awesome, thank you for the quick response! I will begin unwrapping and tracing the harness tomorrow.

Just curious, would I be able to find a short with my multimeter? All of the critical lines are continuous, and display almost zero resistance.

It may work for a lot of circuits if you disconnect your battery (negative side first!) and check each wire to ground.
However if an ignition wire shorts to another circuit it may not show up.

[tkocher92]

I checked the coil feed wires in entirety, and there did not appear to be any short.

I've never experienced this before, the bike can crank and crank without a spark, but if I let go of the starter and try again, eventually a spark will show up.

[navigator]

Hmmm, it's got to be the spark pickup wires near the stator, or the CDI.
perhaps a bad connection?

[tkocher92]

I ran a resistance check on the 2 pickup wires, they read about 1.43ohms which is within spec.

I am going to trace the pickup wires in entirety. I did bypass the clip for those wires.

Is it possible the pickup coil can be bad, and still resistance within spec?

Can I test the signal coming from the pickup coil?

[navigator]

IMO it is unlikely a bad pickup would read good, but I may be wrong.
I'm not sure how to read the signal.
WintrSol is an electrical guru, perhaps he may show up.
You could try to send him a message to check this thread.

[navigator]

How strong is your battery?
A weak battery will give erratic results.
Perhaps all your power is being used to crank the starter, not leaving enough to spark it simultaneously....or dirty start switch contacts.

[Herb]

I have had bad connections and partially broken wires read good on a meter but they would not carry the load.

[tkocher92]

Thank you all for the input and help!

The CDI was bad. It was not sending enough voltage to the coils via the power wire. A jump lead directly from the battery to the coil confirmed this. Used a CDI from an 07 S50, and it is firing every time no issue.