2 Questions from a Noob...

Hi- I just picked up an '85 500 Interceptor for a song (it's a little dinged up and hasn't been run in a few years). I figured it'd be relatively easy, but so far I haven't been able to get it to start.
The problem is that it's only getting spark on 2 of the 4 cylinders- it seemed for all the world like it was a bad ignition coil (when the wires were swapped the spark moved to the other 2 cylinders). I bought another ignition coil on ebay (it said it was tested) but no change in the spark. But maybe they sent me a busted part?

Which brings us to question 1: Is there a way to test to see if the ignition coil is bad on a voltmeter or something?
I also bought both cdi spark ignitors because I read on here symptoms that sounded like my problem- no dice. I should know by now not to throw parts at a bike, but man- I really want this on the road asap!!

Also, I attached a pic of the view under the seat- you can see an electrical plus that, for the life of me, I can't find it's partner. Can anyone help me identify this thing? I'm worried that it might be important...

Thanks for any and all help!!
-Sea Monkey

 

A thousand WELCOMES--no, ten thousand to every adventure-seeking hopeful VF/VFR potential rider. Have good lighting in a small shed or garage cuz you don't wanting to spend hours working outside.


The Honda Official VF500 Service Manual covers almost ALL questions, something to scan on your smartfones before jumping in.

Color-coded wiring diagram would id the plug or whatever.

 

I did download the FSM, but didn't see anything that dealt with my problem...
I've seen methods online for checking whether the coils are working with a voltmeter- that's not something the FSM usually deals with...

 

That plug is for the Clutch diode, If you put the bike in any gear the neutral light will come on but as soon as you pull in the clutch it will go out. The diode is there so the light only comes on when it's in Neutral.Mine was bad and I got a new one from Honda for $13.00.As for the spark problem check all 2 wires going into that coil on both ends as they could have a break at the terminals.

 

So, the diode wouldn't keep it from running, would it?
As long as it's not the thing keeping it from starting, I figure first things first...

 

Nope it shouldn't stop it from running. If you got new(used) CDI boxes and a new(used) coil and it's still not running on all 4 cyl I would check all the electrical connections and grounds to make sure they are making good contact and are clean.

 

Great- thanks!!
I am a little worried that I got sent a bum coil- is there any way to check that it actually works?

 

Using a multimeter they should read around 2.8-3.2 ohms with them unplugged. Just unhook the yellow,blue and ground wires and test both coils on those terminals.

 

Great!- Thanks!!

 

Ok- So I checked the coils and they read fine. The wires have no obvious breaks or anything that I can see. A buddy of mine has a multimeter with probes- is there a way to check if the wires leading to the coils are good? This is driving me crazy!!