PAMCO No spark - bad coil?

dh1989

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Hi everyone,

I've owned my 79 XS650 for about 10 yrs now. It has always been good to me and never left me stranded. After many miles of riding, it finally died on me. It was running fine and I shut it off at a parking lot for maybe 15 minutes. During this time, the key was removed (ignition off). Not sure on kill switch position, but I usually switch it off. When I returned, the bike would crank and turn over fine but would not start. After cranking, if I switched the kill switch off, I would sometimes hear a POP as if the fuel ignited, but no start. I checked for spark and found I had none at either plug.

I have a PAMCO unit (still mechanical advance) with a dual output coil. I think the coil is a 17-6803 coil from MikesXS. Upon disassembly I found that one of the clamps holding the coil to the frame was missing. I don't think this matters since, if I'm not mistaken, dual output coils don't require a ground. I did the usual tests, and found the following:

Battery voltage (ign. off) - 12.2v
Battery voltage (ign. on) - 11.7v
Coil power (+) from kill swith - 8.9v
Pamco green wire (- on coil) - 1.1v
Secondary to secondary - 14,500 ohms
Primary to primary - 2.5 ohms
Primary to secondary - Infinite
Left plug wire - 0.5 ohms
Right plug wire - 0.8 ohms

I did the PAMCO test by removing the locating pin and spinning the rotor with the ingition/kill switch on. No spark. I then disassembled my kill switch and checked for voltage drop. I had 9.6v on one side of the switch and 9.4v on the other. As a final test, I attempted to bench test the coil by removing it and directly connecting it to the battery. I connected the negative primary terminal to battery negative. I then connected the spark plugs and grounded them against the engine block. I connected a wire to the positive primary terminal and quickly swiped it across the batttery positive terminal. I had no spark at the plugs, but a spark would occur at the battery terminal every time I swiped the wire, so there was some current flowing. In an attempt to rule out a bad engine ground, I held the plugs against an exposed piece of the negative wire to the battery. Still no spark when I swiped the positive.

The only thing I haven't done yet is tried different spark plugs. I have BPR7EIX Iridium plugs. They appear in good condition. I checked with my multimeter and had continuity between the electrode and center of the plug, so all appears well.

I would say the coil is bad, but the resistance tests appear normal. Any thoughts before I spend the money on a new coil?

Thanks.
 
Welcome to the forum, dh1989.

Your 'battery spark' test sez bad coil. It's possible that vibration rattle internally fractured the coil, allowing internal spark jumps that may not be physically contact shorting, hence the satisfactory ohm meter test. Can you see any micro cracking around any chafing zone?
 
dh1989,

Try the PAMCO spin the rotor test again, only this time measure the voltage on the green wire. When the first magnet passes over the sensor, the voltage should go low, like, 1.2 Volts. When the second magnet passes over the sensor, the green wire voltage should go high, like whatever the battery voltage is.
 
The PAMCO green wire is reading 0.02v when ignition/kill SW are on. When I spin the rotor there is no change. It reads 0v with ign or kill switch off.

I connected the PAMCO red wire to the kill switch wire for this test (11.07v). I connected one multimeter lead to the PAMCO green wire and the other to battery ground.

I found that the black sensor the green/black/pink wires terminate in is loose (can wiggle it a little).

Bad PAMCO?
 
So you think the PAMCO and coil are bad? Is there any way I can repair the PAMCO?

I'm strongly considering just going back to points. The bike ran better with the PAMCO but points never left me stranded :banghead:
 
With 11.7 volts at the battery with ignition switch on, but only 9.7 or 9.4 at the engine stop switch you have a bad connection between the ignition switch and engine stop switch.
The Pamco can function at very little voltage, 3 volts I think. The coil is the major power draw. It needs more voltage to function.
I have found that testing a coil as you did with hooking to a battery then watching for spark is a bit tricky. On a dual out put coil try using a piece of heavy copper wire, with a loop twisted in each end just large enough to screw a plug into the loop. Put both plug in the loops.
The secondary circuit runs from the coil down one plug wire to the plug, jumps the gap to the shell of the plug. Across the engine to the other plug a shell, jumps the gap up the plug and wire back to the coil.
The coil doesn't really ground to the engine, just uses it to carry voltage from plug to plug. The copper wire does this. I use a piece of wire out of a piece of house wire. It's solid and stiff enough to hold the plugs.
Do this then try hooking to a battery.
Leo
 
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