sporadic spark

[goggleboy]

I have a 78' GS750 that feels like a 450. I had a timing light hooked up to the spark plug wires while it was idling and I noticed that 2 and 3 had a consistent flash (indicating a spark) but when I hooked up the timing light to 1 and 4 wires there was more of a sporadic flashing, not a consistent strobe. Also to note, the higher i revved the engine (past 2000rpms) the timing light would flash more consistently on 1 and 4. It would almost hang above 1700rpm, then go back down to idle with a sporadic flash again.
To further proove what was going on, when I pulled the plugs 1 and 4 where darker and sooty more so than 2 and 3.
Keep in mind I have new dyna coils, electronic ignition, and plug wires.
Do you think this is a timing issue or a dirty connection?
any advice would be great

 

[chuck hahn]

Did you take off the points cover and check the timing marks?? Did you recheck all the connections to, be sure they arent loose or corroded? Did you check down the wiring harness a ways back from the plugs to be sure there arent any hairline cracks in that old hard plastic wire covering that would cause a static short to the frame? Notice any arching marks on the bottom of the frame tubes where they clamp in?? that sort of stuff is what you want to be looking for. How about the condensors? What about the resistors in the plug boots? You do know about the resistors, right?

 

[SqDancerLynn1]

Could be a bad condition, or just nothing. I get that ghost signal with my timing light too. Bike runs fine.
Make sure you have 12 Volts on the coils. Have you done a carb sync

 

[chuck hahn]

and adjusted the valves..which should be done before a carb sync..

 

[goggleboy]

Yeah, its just funny how the signal would change as soon as I switch
between wires. Also, 1 and 4 are the left coil correct? There might be a problem right there. Resistors in the plug boots?
Its funny because each spark is good and purple, just possibly not
firing correctly for some reason. I followed the directions on how to time
the Dyna S system, I did this statically, while turning the crank and listened to the snap of the spark plug. Does the "F-2" mark line up with the stationary mark for cylnder 3?

edit: I have adjusted the clearances to spec, and no, I havn't done a good synch. just a bench synch

 

[Guest]

Adjust them with a timing light. I found that I had to adjust the right hand module a bit to get the timing dead on after being set statically. Are you using the stock coils and wires?

 

[chuck hahn]

yes ...resistors in the plug boots. If you look in the boot with a flashlight youll see a slot for a screwdriver..Unscrew the plug and theres a spring and resistor in there..if you have resistor caps. Take the resistor out and get some 1/8 inck brass rod and cut pieces as long as the resistors and youll now have a regular plug and not worry about being shut down in BFE from a bad resistor.