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Faulty pick up coils? 3 weeks 3 days ago #30679

  • PaulD
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My bike is still testing me to the limit. After stripping and cleaning the carbs yet again things are getting worse and not better. I know all three tiny ports in the venturi are clear as I’ve squirted carb cleaner through the air bleed in the back (filter side) of the carb the small jet under the cap in the carb body and the idle mixture screws. All three ports now have a good equal spray pattern. The float heights are correct 7.5mm, the diaphragms are good and everything else looks good. Using Scotches tool the lacquer thinners comes out clean with no discolouration. I’ve put a brand new set of Denso plugs and new coils on the bike and removed the ballast resistor. I tried running a direct power lead to the coils thereby cutting out all the old wiring and connector blocks but still no different. There is a spark to the plugs but it’s really weak and no different to what it was before? Someone suggested that the pick up coils maybe loosing their magnetism? And that I need to check them for resistance with my multi meter so I’ll do that next. To top it all it looks like the mechanical seal on the water pump is leaking as I’ve got a steady drip of coolant from the housing on the front of the crankcase! 
so guys any help, hints and tips will be very welcome as elektrikery isn’t my forte, I class myself as an electrical idiot 

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Faulty pick up coils? 3 weeks 3 days ago #30682

  • Kawboy
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I feel your pain. Electrical diagnosis is not for everybody. The Service Manual does a pretty good job of describing simple tests of major components and suggested replacements but you do need to understand some basic fundamentals in order to get things fixed.

First question- What model are you working on? The  79's and 80's have one type of primary ignition and the 81's have a different system and it matters. We can't properly help without that info.

Please note- The Igniters are very sensitive to too much power going through the Darlington Transistors. It's critical that the primary resistance of the ballast resistor + the primary resistance of the ignition coil be maintained above 2.7 ohms otherwise, you will most likely burn out the Darlington Transistors. They are the switches that turn on/off the power to the coils and trying to push too much power through the Darlingtons will fry them.

You stated that you replaced the ignition coils- with what?? What is the primary resistance of the coils as measured across the + and - terminals. If it's 2.7 ohms or higher ( up to 3.8 ohms) then you can get away with removing the ballast resistor. As an example, Dyna makes 3.0 ohm coils for wasted spark and they could be used without the ballast resistor. If your coils measure less than 2.7 ohms, stop any more testing/running until you put the resistor back in the circuit. And do the resistance test of the resistor on all 3 leads. The resistance should be 1.5-1.9 ohms on each of the 3 leads. If the resistance is more than 1.9 ohms, the resistor is starting to burn out and will fail soon. It's not likely to find the resistance lower than 1.5 ohms.

All electrical tests assume that you have a fully charged battery capable of turning over the engine on the starter and maintaining a minimum of 9 volts at the battery during cranking. If the battery is weak, then all of your testing results are meaningless. How many people have been caught by this faux pas (mistake) would make your head spin.

So, if you report back on these items, we should be able to guide you further.

KB
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Faulty pick up coils? 3 weeks 3 days ago #30683

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I’ve checked with my multi meter and got the following readings on all three coils. 3.5 ohms across the thin wires on all three. 18k direct across the threaded HT pins in the coils and 28k with the leads and caps fitted. The caps are NGK and marked up 5k ohms. So all you electrikery wizards do these numbers seem to be in the ball park? I’m aware that I will have to remove the ballast resistor as my new coils read 3.5 ohms.

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Faulty pick up coils? 3 weeks 3 days ago #30684

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Sorry I forgot to mention, my bike is a 1979 A1 KZ1300

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Faulty pick up coils? 3 weeks 3 days ago #30686

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I agree with your assumption that the coils and secondary wires are within spec so let's move on. 
There's a test on page 242 in the Service Manual titled "Operational Inspection of the Ignition System ( without the pickup coil) and this test should be your next test. it calls for the use of the "Electrotester" and you can perform this test without having this special tool when you understand the basics of the wasted spark ignition system, so I'll explain this first.

Wasted Spark System- A very common ignition system used in many multi cylinder  engines since it saves on the cost of ignition system parts. Basically, the ignition coils fire 2 spark plugs simultaneously. One plug is fired on top dead center compression and the second plug is fired on valve overlap. The spark that happens on valve overlap is "wasted" since it's not required. Now, what you need to understand is the flow path of the secondary high voltage through the spark plug wires and the spark plugs. When the voltage in the primary windings in the ignition coils is energized with 9-12 volts, it creates a magnetic field around the primary windings and when the primary voltage is opened, the magnetic field collapses on to both the primary windings and the secondary windings which creates a high voltage output in the secondary windings able to jump and air gap in the spark plug. In a wasted spark system, that voltage runs down one spark plug wire and crosses over the gap in the spark plug to the "ground" of the cylinder head and across the cylinder head to the spark plug associated with second plug of the same coil, and then jumps the air gap of the second spark plug and back up the spark plug wire to complete the circuit. One spark plug fires from the center electrode of the spark plug to the ground electrode of the spark plug and the second spark plug fires from the ground electrode to the center electrode. This is the reason we have now available double iridium or double platinum spark plugs to extend the spark plugs life. You need to understand the statment in bold before continuing testing.

So, how to perform this next test without the "Electrtester" - You can basically follow the test as written in the manual but instead of attaching the secondary leads to the tester, you're going to point the ends of the 2 secondary wire ends of the same ignition coil at each other and space them 8mm apart and then perform the test. This replicates what happens when using the Electrotester. You should see the spark generated by the coil. if you don't see the spark, try moving the ends of the 2 secondary wires closer together down to 5mm apart. 8mm apart would be a healthy spark, 5mm would be a minimum standard spark. By doing the test as described in the manual, you're supplying the primary circuit with voltage and this confirms most of the wiring in the primary and secondary circuits. So, let's see what you find after this test and we'll go from there.
KB
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Last edit: by Kawboy.

Faulty pick up coils? 3 weeks 2 days ago #30689

  • dcarver220b
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I agree with your assumption that the coils and secondary wires are within spec so let's move on. 
There's a test on page 242 in the Service Manual titled "Operational Inspection of the Ignition System ( without the pickup coil) and this test should be your next test. it calls for the use of the "Electrotester" and you can perform this test without having this special tool when you understand the basics of the wasted spark ignition system, so I'll explain this first.

Wasted Spark System- A very common ignition system used in many multi cylinder  engines since it saves on the cost of ignition system parts. Basically, the ignition coils fire 2 spark plugs simultaneously. One plug is fired on top dead center compression and the second plug is fired on valve overlap. The spark that happens on valve overlap is "wasted" since it's not required. Now, what you need to understand is the flow path of the secondary high voltage through the spark plug wires and the spark plugs. When the voltage in the primary windings in the ignition coils is energized with 9-12 volts, it creates a magnetic field around the primary windings and when the primary voltage is opened, the magnetic field collapses on to both the primary windings and the secondary windings which creates a high voltage output in the secondary windings able to jump and air gap in the spark plug. In a wasted spark system, that voltage runs down one spark plug wire and crosses over the gap in the spark plug to the "ground" of the cylinder head and across the cylinder head to the spark plug associated with second plug of the same coil, and then jumps the air gap of the second spark plug and back up the spark plug wire to complete the circuit. One spark plug fires from the center electrode of the spark plug to the ground electrode of the spark plug and the second spark plug fires from the ground electrode to the center electrode. This is the reason we have now available double iridium or double platinum spark plugs to extend the spark plugs life. You need to understand the statment in bold before continuing testing.

So, how to perform this next test without the "Electrtester" - You can basically follow the test as written in the manual but instead of attaching the secondary leads to the tester, you're going to point the ends of the 2 secondary wire ends of the same ignition coil at each other and space them 8mm apart and then perform the test. This replicates what happens when using the Electrotester. You should see the spark generated by the coil. if you don't see the spark, try moving the ends of the 2 secondary wires closer together down to 5mm apart. 8mm apart would be a healthy spark, 5mm would be a minimum standard spark. By doing the test as described in the manual, you're supplying the primary circuit with voltage and this confirms most of the wiring in the primary and secondary circuits. So, let's see what you find after this test and we'll go from there.
KB

 

Worthy of printing and saving in the FSM, Thanks!
 
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