1992 FXRS with
Dynatek 2000 ignition module
Screamin eagle dual fire coil and cables
Autolite XS65 plugs
92 Octane Gas

I have scoured these forum and haven't found anyone listing similar symptoms, or maybe my nonprofessional diagnosis is way off ? Apologies if this is in the wrong place of has been answered before....

Fires up perfectly, idles great, no prob with combustion shifting through all gears BELOW 3000rpm.

As soon as I hit 3000rpm, in any gear, engine jerks and tach drops a few hundred rpm, sporadically. This situation worsens with increased speed past 3000rpm/60mph.

I checked the ignition module. The microprocessor and guts are encased in urethane so it was more just a visual check. All pin connectors functioning, no corrosion, etc. The Purple VOES wire is NOT CONNECTED. Diagnostic/Static Timing LED on back of module flashes with throttle. All rev limit switches are not loose, no visual problems.

Spark Plug Cables good.

Any suggestions? "Ah ha!" moments?

 

I switched out the plugs, wires and coil each individually and ran at 3000RPM both loaded and unloaded. Each yielded the same misfire result.

Thoughts on ignition module vs .... ?

 

90% odds on that its the Ignition module.

I was hunting a similar problem a couple of years ago - swapped out the plugs, wires and coils and still the problem was there. To all intents and purposes the Ign module looked fine, but once I replaced it with an Ultima unit the problem went away!

have a look around as you can pick up an Ultima for $100-$150 (if it comes with coils - throw them in the bin as they are total chit)

 

Thanks GraemeR

I'm hoping this solved the issue, though I'm not sure I believe it just yet.

Yesterday afternoon I swapped coils with my 1991 XLH. Same issue. Switched the coil back.

Then swapped spark plug wires. Bingo. I noticed when removing the screamin eagle wires from the original coil that the fit was not tight. Now, this could have been my fault after removing them numerous times in the past week or so, but I ahd not noticed them to be this loose before. So, I crimped the ends a bit so they won't loosen up at the contact, particularly at highway speed. Took it for a test ride up and down the highway a few times:

No issues sitting at 3000rpm in 4th or 5th gear under load.
No issues with wide open throttle past 3000rpm pushing well past 90mph.

Now, my question is, if it really was the spark plug wires this entire time, why would I only notce the misfires at higher speed, and so predictably at 3000rpm? I never had a starting, idling or low speed issue.

Oh well. I'm crossing my fingers that that was it.

On a side note, I emailed Dynatek and they offered a diagnostic exam of my ignition module. I really don;t think that is the issue after riding like I did last night. But, I will e on the lookout for another for when this one poops out.

Thanks!

 

That sort of makes sense.... It could be that the spark had to jump from the end of the leads to the top of the sparkplug. At low speeds you can get away with this, but at higher rpm then you only need 1 or 2 sparks to go astray and arc to earth or just be plain weak that you could get the problem you describ.

Well done on tracking it down as intermittant Ign issues can be a real bastard to get to the bottom of.