Honda Shadow Forums banner

1 - 6 of 6 Posts

·
Registered
1986 Honda VT1100, 1980 Honda CX500D, 2013 Honda Ridgeline
Joined
·
5 Posts
Discussion Starter · #1 ·
New to me 1986 VT1100. Rear coil is not firing. Are there any coils that will fit in this without modification? Are there certain brands of coils that are better than others? Or more reputable places to buy a coil?

Thanks for your help!
 

·
Registered
1983 Honda vt750 Shadow
Joined
·
16,207 Posts
First swap the 2 coils to see if it really is the coil. Just changing to new ones won't cure a bad ICU or pulse generator.
And measure the resistance of the plug wires and end caps.
 
  • Like
Reactions: MichiganJason

·
Registered
1986 Honda VT1100, 1980 Honda CX500D, 2013 Honda Ridgeline
Joined
·
5 Posts
Discussion Starter · #3 ·
First swap the 2 coils to see if it really is the coil. Just changing to new ones won't cure a bad ICU or pulse generator.
And measure the resistance of the plug wires and end caps.
How do I diagnose a bad ICU or pulse generator?

I swapped the 12v leads going to the coils and had no spark anywhere. When I switch them back, I get good spark at the front two plugs and intermittent spark at the back left. Still nothing at back right. I'm checking spark using a timing light.
 

·
Registered
1983 Honda vt750 Shadow
Joined
·
16,207 Posts
Are your plugs clean and gapped correctly?
Are both spark wires from one coil going to the same cylinder? And the other coil, 2 plugs on the same cylinder?
They fire 2 plugs in series from each coil.
You can measure resistance of the pulse generators at about 450-550 ohms each. They have been known to go bad.

294154
 

·
Registered
1986 Honda VT1100, 1980 Honda CX500D, 2013 Honda Ridgeline
Joined
·
5 Posts
Discussion Starter · #5 ·
Yes, both spark plug wires from the coil are going to the same cylinder.

So, for clarification, are you saying that if the right hand spark plug isn't firing, then the left won't fire either because they are in series?

I checked plugs and wires. Plugs are between 4.8k and 5.5K ohms. I cleaned the plugs, but they are in decent shape. And wires are showing 5-6K ohms. The plug wires look original (thread onto the coils), so probably overdue for replacement, but that doesn't seem to be causing the current issue. (sorry, bad pun).

I will try to check pulse generator resistance next.

Thanks for helping the newbie!

Jason
 

·
Registered
1983 Honda vt750 Shadow
Joined
·
16,207 Posts
If one side plug is fouled it may cause the other side not to fire. If it is shorted the other one should still work since the current will just go to the head a ground anyway.
 
1 - 6 of 6 Posts
Top