[Sky Rider]

At this point, have you pulled the plugs and spark tested them against the engine to visually see if they have spark? It's easier than testing with lights.
I still think it's a wire issue in the system.

 

[PoggiPj]

Hey Jim,
Yep - took the plugs out tonight and checked them against the engine for spark. First of all, it looks like both front plugs have never been fired. They look brand new and are wet with fuel.

Rear plugs fire fine. Front plugs get a small bit of spark for about a second, then the spark stops entirely. So I started replacing the wires, and the threaded coil cap is so brittle it split in half!

Anyway, since it's both front plugs, I suspect the coil. Is there a way to test the coil separate from the plugs?

 

[Sky Rider]

I think you would be better off just replacing the wires first and see. The coils don't go out very often on our bikes. (One of the few electrical parts that doesn't). If the plugs spark after you replace the wires, it's probably because they got so brittle the cores fractured someplace causing an open. If the spark was weak, the current probably has to jump across a gap in the wires or it's getting dumped to the engine case somewhere. I used to get a great arc and spark light show from my right front plug cap where it touches the metal casing on the throttle cables. I had to use a bunch of electrical tape to stop it and I really need to replace my wires and plug caps on both cylinders.
I don't know of a way to test the coils separatly outside of ohming them out with an ohmmeter. If they pass the resistance test, that's about all I know how to do short of grabbing a terminal while the engine is running and seeing how much of a jolt you get. I don't recommend this however!! Slim may have some other tricks up his sleeve though.

 

[bullwinkle]

PoggiPJ,
All I can say is I must be one of the lucky ones then, because I did have one of the coils go out on my 85 700. According to the book there are two ways to test the coil

OR

My coil went because the junction box (as it was inspected closer upon removal) had some acid drip inside and arc between the connections inside. The only evidence from the outside was a tiny hole behind the rubber on the outside of the JB.

 

[PoggiPj]

Charlie, that was some excellent documentation. Thank you

I couldn't test the spark arc gap, since there isn't a spark to arc.. lol

But I did test the resistance. The primary is fine. 2.2 ohms. The secondary, however is 43.3 Kohms. That is way out of range. Since neither of the front plugs are firing, I'm inclined to think it's the coil.

So now the question is, do I go with a new OEM, or with aftermarket like Dyna. What do you recommend? Also, if I upgrade the front coil, must I also upgrade the rear? That rear one looks like it can be a real PITA to replace.

 

[Sky Rider]

The rear isn't too bad. I took mine out so I could reposition the EPA spider in the back.
You could also get a used coil from someone here or on ebay.
There was a link awhile back where someone replaced their coils and they came as a set, IIRC.

 

[PoggiPj]

Hi Jim. I checked eBay. None at the present time. I saw a pair of Dyna's on DennisKirk, but the hole orientation doesn't work for our bike. $147 for a pair.. The OEM coil (21121-1124) is available on RonAyers for $75.

 

[Sky Rider]

You just have to get auto type plug wires or crimp that style end on the wire. Other than that, they should work just fine. Not stock, but I'll bet the OEMs are more expensive.

 

[Sky Rider]

Yup, Ron Ayers is 75 just for the front coil.

 

[bullwinkle]

I think if you shop around most are in the same ballpark
http://www.motogrid.com/pages/parts/viewbybrand/parts.aspx
21121 SKU: 21121-1124 COIL-IGNITION,FR 1 $69.91

Just to be sure, I would try switching the coils around (using the rear connectors with the front coil and try to get a spark from the coil that way (ruling out additional electrical problems) and even using the rear coil with the front connections, just making sure it is the coil.
Coils are supposed to be like light bulbs, working or not. On my kz440 I had a coil that was going out for about three days of daily commuting, then finally gave up the ghost, bigger difficulty there only one coil - bike no go :-(
Good Luck
PS I didn't write it up I just copied and pasted.

 

[PoggiPj]

What is involved in getting that rear coil out? It looks like a PITA.

 

[bullwinkle]

It is bolted on the battery box, back to the manuel:

 

[PoggiPj]

when I was putting wires into the rear coil, it was nearly impossible because of some junction that appeared to be coming from the radiator. My wife had to hold it up out of the way so that I could get the wires into the coil.

 

[bullwinkle]

Aaaahh The bond the wife and the bike have, both can get you cursing and both can help distract you from cursing.

I believe what you are talking about is occasionally called the spider. It is actually part of the emission controls. Two hoses come from it and one to each cylinder and one to the air box up under the gas tank.
I think you knew this was going to be as you said a PITA, right? It will be worth it when things are running great and you know it is because you took the time and did it right!!

 

[PoggiPj]

Is there a way to kill that spider? It's in a nasty spot

 

[ChrisC]

You can coaster or marble and lose the spider. Basically, you block off the reed valves and plug the right carb vacuum hose, remove the spider and block off the remaining hose to the surge tank. Lots of posts on this out here.

 

[PoggiPj]

You know, if I told anyone else that I was going to coaster or marble my spider I'd probably be hauled away someplace.

 

[Sky Rider]

Actually, you may want to check your inspection laws before you coaster the bike. It's getting harder to mod the intake and exhausts on any engine these days. You can marble and leave everything in place, just remove the marbles when inspection time comes up or you could coaster and replace it all if needed at inspection time.

If you don't have emissions inspections for bikes, coaster away. BTW, you're not coastering the spider, just the reed valves but it kills the spider none the less.

 

[PoggiPj]

Has anyone ever discussed relocating the spider instead of marbling and coastering - just to provide better access to the rear coil?

 

[Sky Rider]

The rear coil is easily accessable if you uninstall the battery box. This isn't hard, it just takes a bit of time. You will have to remove the junction box and the IC ignitor and of course the battery, but once it's out, the coil is right there. You can just raise the battery box up to where the coil is more accessable if you want instead of taking the box completely out.