Hello (again) and a question about plugs

Hello.  I used to post on kz650.info but that forum seems to be gone : - (

So now I'm over here.  I was 'Renthorin' over there and that user name exists here so I must have signed up at one point but the email I used is no longer around so I can't do the whole forgot password dance.

Anyway, I've been riding the 650 all over the place and when I went to ride to work Wed she was running on 2 cylinders.  I did the hand on header pipes test and it was 2/3 cylinders that weren't firing.
After many tests I confirmed the following:
1) coil for 2/3 is in perfectly in range for primary and secondary windings.
2) condenser is spot on.
3) no loose or corroded wires.
4) power at all appropriate spots.
5) I removed plugs 1 and 2.  No spark on plug 2 but I did have spark on 1, as expected as that header pipe was toasty.
swapped power to coils so 2/3 became 1/4 and no spark on #2.  That's odd.  So it's not a coil issue.  Put wires back as they go.

I put plug 1 into wire 2 and got a spark.  Huh.
Put plug 2 into wire 1 and didn't have spark.

I then checked the resistance on plug 1 and it was very low.  .01 or the like.
I then checked the resistance on plug 2 and it was really high.  That made me think the plug was bad.  Same thing for plug 3

Got new plugs and she's running great.

Here is my question (finally, right?)  - what would cause the plugs in 2 and 3 to go bad or be bad?  They are on the same coil, same condenser, same point.

Thanks,

Will

WElcome back Will
Didn't you ride in our flag across America event ?
Dave

I did indeed
Was just talking about that with my friend who rode with us across Michigan. 

He and I are headed up into Ontario in a few weeks to ride 129.

Cyl 2 & 3 run hotter than the outer cylinders so this may have a bearing on plug life ?

I thought so.
Welcome back
Dave

That's awesome.  I'd forgotten about the pictures.

Plugs 2 & 3 are the same coil. You mentioned you have power to the coils but dont say how many volts to each.
low voltage will cause a weak spark and cause sooting which will kill plugs pdq.

I didn't write it down but with the engine off it was low 12's high 11's for both coils.  The plugs were all a bit sooty so I'm running a little rich I suppose. 

It had been maybe 10 years since I changed plugs so shame on me LOL.  She has shiny new ones now and fired right up : - )

I have thought about switching to the green coils and the electronic ignition in stead of the points but honestly with the exception this week she runs like a champ and I hate to mess around with things if I don't need to.

If I break down in Canada it will be an adventure!

Sometimes you don't know what happened and you just know it's fixed.
You could have had multiple issues but changing the plugs has fixed it.

Just a personal opinion---i would keep the points for now and just ride it.
Unless, you like working on your bike as fall approaches to sort out a new ignition system.


Send a closeup photo of the old plugs. 

Also, pull the new plugs after a few rides to see if they are sooty like the old ones.

No, I'd rather not mess around with the ignition if it's working which it is now  

This is about as close as I can do with my 6-year-old Samsung phone. 
 

Welcome back!

Yes, "never touch a well-running system," and my philosophy has always been: points ignition will always get you home—there’s always something you can tweak on the road to keep you moving... whereas if an electronic ignition fails while you're out riding, in the vast majority of cases, it means getting towed or leaving the bike behind.

(I personally ran a very early Dyna ignition for 20 years without issues—the one with the black box featuring the "frame-tube cutout"—but I always carried a complete, original points ignition setup in the Z1B’s rear storage compartment for emergencies...)

 

Those are great pictures!