1989 SB50P No Spark

[johnkiniston]

Howdy,

I just picked up a 89 SB50P and I have no spark.

I've swapped out the cdi for a known good one from an Elite 80, I swapped out the coil for one from a Spree.

I did the tests in the manual:

Ignition Coil Primary - pass
Ignition Coil Secondary - couldnt get this one to work, tried three coils (one known good from the ELite 80)
Pulse Generator Coil - pass
Exciter Coil - pass
Ignition Switch - pass
Engine Stop Switch - pass
Ground - Pass

I still have no spark.

I've tried both kicking the bike and using the electric start.

Does anyone have a suggestion as to where I should look next?

We did have the seat off to remove the oil tank and gas tank for cleaning.

[mousewheels]

johnkiniston.
Hi and welcome!

You have done a good job trying to isolate the no spark condition. Seeing how you have swapped out the CDI and Coil and checked out the Ign switch and grounds - Compare resistance readings for the stator coils - exciter and spark trigger with another SB50 owner. Honda gives a pretty large range for the coil resistance checks - and I've found bad coils that checked out ok from the service manual resistance checks.

When coils fail with shorted turns, the resistance can vary by very little, depending upon *where* the shorted coil is. But a short will pretty much kill the output, leading to no or weak spark.

[Clivester]

Check the resistance on the white wire from the alternator/stator to make sure it is in spec. and the connectors are tight.

From the CDI harness connector, check continuity of the green wire and the black/yellow wire from the connector to their connectors at the coil.

And umm the engine stop switch is not engaged?

[veedubh20]

change coil , dont mix up wire,

engine switch turn run , not off

just unplug wire harness from ignition key

[johnkiniston]

johnkiniston.
Compare resistance readings for the stator coils - exciter and spark trigger with another SB50 owner. Honda gives a pretty large range for the coil resistance checks - and I've found bad coils that checked out ok from the service manual resistance checks.

OK Now this is interesting.
Per Honda the range for the Exciter coil is 500-900
My Exciter coil reads at 666, That's kinda spooky.
My friend Slynch's Coil reads at 889 on a Spree that was providing spark but had blown its CDI.
The engine he just purchased that came out of a running Spree reads 693.
And finally 'Timmy's' Coil is at 717.

I'm probably going to try to swap in Timmy's for mine when I'm feeling up to the task, It's a wee bit late and cold tonight to try.

Per Honda the Pulse Generator range is 50-200
Mine is at 112
Slynch's Spree with the blown CDI reads at 117
And the Engine he just bought reads at 112.

I'm going to say my Pulse Generator Coil is OK.

[johnkiniston]

It Starts!

I changed out the Exciter Coil from the one from 'Timmy' and swapped the CDI box with my Elite 80 and it'll kick over and run.

The Funk of Forty Thousand Years came out of the exhaust, * it still is coming out but its running!

Now I have to debug the poor performance and bogging down. Next two questions are:

Where can I get an inexpensive compatible CDI box?

And what kind of air filter element should I use? Mine biodegraded

[Wheelman-111]

Greetings:

A used Honda CDI is probably preferred over a new one made who-knows-where. May I suggest Honda dealer for your filter element? If you decide to go pod or K&N, your carb bellmouth is just over 1" diameter. You may be able to finagle an angled pipe if shock interference is an issue.

I changed out the Exciter Coil from the one from 'Timmy'

-So pleased his Heart beats again! I admire your persistence in tracking down this issue and resolving it.