Working on '84 fxst evo/ 5 speed trans. Problem with ignition, bike was taken to independent shop for upgrade. They installed dyna s pickup with mechanical weights, bypassed ecm and hooked directly to coil. Rode 2 times then stopped running. I suspect it was a fuel issue at first, which has been addressed. Now i have very weak spark and when I turn ignition switch on with spark plug tester on plug the light flashes. Would that indicate bad switch or because ECM was bypassed

 

Stock 84 FXST would not have an ECM, and it would be a 4 speed kickstart. No telling what you're working with, so not enough info to help.

 

Post up some pics of the bike. It will go a long way in letting us know what u have going on.

 

Actually it did
http://partsfinder.onlinemicrofiche....OIL%20ASSEMBLY

MTM123
If your bike worked before something changed and now it doesn't work the source of the problem is most likely what was changed.
If I were you I'd pull that Dyna S and go with a Dynatek 2ki instead..JMO

 

There is no ignition module on the Dyna S when using the centrifugal weights.. Here is a link to the installation instructions..
https://www.wwag.com/step/pdf/104729.pdf
Sounds like it's a single fire ignition that uses two Five ohm coils. Or a single coil with 2 primary's ( 3 studs, middle is battery 12v, upper and lower studs are for the trigger from the ignition plate for the black and white wire). You will need to measure the resistance of the primary of your coils... You should have 5 ohms.. If you don't have the proper resistance , it could be over heating the coil...

 

Here is the info, installed ultima twin twin fire 2, with d6-4 coil, 1(+) 2(-) posts, single fire, voes hooked up I rebuilt s&s super G . Starter solenoid, clutch hub replaced new bars ,control switches, Badlands flasher module , all wiring checked, connections cleaned/replaced .fuel supplied and strong spark. Won't start. When cranking over sometimes the starter doesn't turn motor making a whirring noise, tap starter switch and will turnover. Kickstarter arm starting at 12 o'clock ending at 6 o'clock will travel to about 8 o'clock before engaging. These two issues plus not getting it to fire up are they related

 

That bike had an ignition module, not an engine control module.

 

I figured the OP was referring to the ignition module as an electric control module and I have heard some people refer to their ignition module as an electronic control module.
I even posted a link to his bike showing the module but I guess it doesn't work now.
I hope that clears things up for you.

 

I thought all single fire coils were 3 ohm...
As for the rest if you have fuel and spark then your problem has to be timing.
Whiring noise is usually a starter clutch.

 

I'd like to help but I never heard of an Ultima twin fire 2...