Coil secondary measurements

[garyS-NJ]

I'm working on this '86 that runs good once warm but is hard to start and slow to warm as the cylinders come in.. It needs choke of course to start and warm but the choke does not appreciably raise the idle. I know this sounds like a plugged choke circuit but I've had the carbs off a few times (just never pulled the choke plungers as I thought I had to separate to individual carbs for that), so I'm checking everything else first....

I tried swapping in my ignetek ignition which didn't help. Seems warm or cold I'm losing 1 volt from my battery through ignition switch... And measured the coil primary and secondary windings and pick up resistance. Primary windings and pickups are in spec. Secondary's from +12v in through the spark plug cap were 23k ohm vs spec 10-15k ohm (was I supposed to remove spark plug caps for this measurement or does the spec take into consideration the cap resistance?). I recently trimmed back the plug wires and measured plug caps around 9k ohm. Can't see how all four coils could be temperature sensitive like that.. I have seen them intermittent open with temp, nor can I see plug caps intermittent like that but perhaps... So I ran it for a while with choke open and idle up burning fuel and strong sea foam and carb/injector cleaner mix. Then sent owner away telling him to be patient warming it and ride two tankfulls with strong sea foam (8 oz per tank).

 

Back to coil secondary measurement?

 

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[bongobobny]

OK first, 1 volt loss through ignition switch is sort of normal. Second, not sure why you are measuring coil secondary with ignition voltage present? Readings should be taken with no voltage applied, a voltmeter is actually reading a voltage when it is reading ohms. Also how sure are you of the accuracy of your meter?? Buy a resistor of the approximate value you want to read and measure, I have seen cheap meters be waaaaaay off on their readings...

 

Reading should be from the actual coil secondary, not through the spark plug wires...

[garyS-NJ]

I didn't have the ignition on to check resistance. Good idea on checking the meter. But the to check the secondaries, are you suggesting to take the plug wires off the could? Would be much more work to access the coils and pull the wires off but I could take the plug caps off...

 

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[bongobobny]

Yes, remove the wires from the coils. Otherwise you are also reading the resistance of the wires as well...

 

The easier way is to get a spark gap measure and check the length of each spark to spec. It will tell you the condition of each system. Can't remember the spec offhand but I think it is over 0.100 inch. It's somewhere in the service manual.

[yamagrl]

Yes, remove the wires from the coils. Otherwise you are also reading the resistance of the wires as well...

 

The easier way is to get a spark gap measure and check the length of each spark to spec. It will tell you the condition of each system. Can't remember the spec offhand but I think it is over 0.100 inch. It's somewhere in the service manual.

 

 

Here is the spec from the 86-93 manual. Min spark length is 6mm roughly 1/4"

 

[garyS-NJ]

So the wire and coil should total no more than 5k ohm. I'm thinking the coil is most of that 5 k ohm. I'm going to try another meter and test through the plug wires to the Tci connector as it isn't easy to access the coils with fairing on bike.

 

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