Can a coil go half bad?

[Incubus]

I thought I saw a thread like this recently, but I couldn't find it when I searched, so I'll just go ahead and ask.

After tuning on my carbs today I decided it was time to set the air screws. Grabbed the Colortune.... since I managed to lose a part of my Colortune - the cable looking thing that actually allows you to hook the mechanism up to the plug cap - I started pulling the plugs to set the screws by color. One and two are a beautiful tan (bear in mind, this is only from sitting on the centerstand getting a carb synch) and three looked a little lean so I riched it up some. No. 4, however, was coated with fuel (at least the pilot circuits are clean). I put a new plug in the cap and grounded it to a head bolt and there was no spark.

I trimmed back the plug wire a bit until I found clean copper and put on a new cap and grounded it again. Nothing. I now understand why my bike only wants to idle at about 1700 rpm (onboard tach, so estimate only).

The plug wire has no obvious breaks and the insulation appears unmolested. There are no dramatic bends that could indicate it had been twisted or broken. And since No. 1 is firing just fine I figure I must have continuity and the pickup wires should be OK.

Can a coil go half bad? Or is there something else I should check?

Patrick

[petejw]

Hey Succubus,
Not to sure bout the coil, but grab an ohms meter
and you can check the resistance of the coils/leads and plug caps.
I had something similar but only when the bike was hot,
was the plug cap.

[oseaghdha]

My 2-3 coil did just that. #3 was fine , but #2 was weak/ intermittent.
It wouldn't idle fer $hit, but ran fine above 2K RPM.

I think it was headed South for a long time. After replacing it, the bike is a joy to drive around town. Warms up faster, takes off flawlessly.

Prior to, it was a temperamental/bi-polar/schitzo PITA.

[Incubus]

Thanks, guys. I checked the resistance across the one and four coils and I got no reading. My ohmeter would not acknowledge the coils on any setting. I checked the one-four coil from a set in my "Generally Known to Be Bad Why Am I Holding Onto This Junk" box and got a good reading. Plugged them in and got fire.

Know I remember why I'm holding onto that junk.

Patrick

[xs11widowmaker]

i have a similer problem. I had my carbs off and set my floats and when i put everything back together number 3 and 4 are not firing. im getting a good reading thru the caps and wires but they dont fire. plugs arewet with gas. could someone help me please. thanks

[oseaghdha]

i have a similer problem. I had my carbs off and set my floats and when i put everything back together number 3 and 4 are not firing. im getting a good reading thru the caps and wires but they dont fire. plugs arewet with gas. could someone help me please. thanks

Take the plugs out and lay them on the head, crank it and look for sparks. Move them away from the plug holes!
3 and 4 are on different ignition circuits. If you get sparks, maybe they are switched, or you flooded it.

[xs11widowmaker]

i just put new coils and wires on it so they wont cross(not long enough)
could it just be flooded?

[oseaghdha]

i just put new coils and wires on it so they wont cross(not long enough)
could it just be flooded?

What coils did you put on?
Did you check to see if the ballast resistor should be removed?

[Incubus]

If you have a 78 or 79, your stock coils are 1.5 ohms. If you went to higher resistnce coils, say 3.0 Dynas or Accel, you need to take the ballast resistor out of line. If your bike is an 80 or 81, the coils might be 2.5 or 3.0 ohms stock.

Patrick

[xs11widowmaker]

its an 81 with no ballast and i bought the mikes coils