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Jet needle improves acceleration. 20 Jul 2011 06:48 #463894

  • Patton
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calvin17d wrote: ...battery terminals and measured 12.5-13V with the bike off...3000 rpm and measured 15V at the battery....9.5-10V at the red/yellow wire on each coil. Measurements should be 12.5v here as well correct? Thoughts on the voltage readings above?


That's an unacceptable voltage drop in voltage before reaching coils.



Good Fortune! :)
1973 Z1
KZ900 LTD
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Jet needle improves acceleration. 20 Jul 2011 21:10 #464024

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I've been following this thread seeing how your jetting turned out. I just bought an 81 LTD 1000 that had a weak spark. I spent a few hours and a couple of contact cleaner induced headaches trying to stop my voltage drop to the coils and ended up doing the 12v relay trick as seen on Wiredgeorge's website. I was getting 10.3 to the coils and found I lost over 1v just thru the kill switch:unsure: I picked up a relay for under $10 and mounted it behind my right side cover. Now i have 12.5 clean volts and a fat spark! My bike idles better, doesnt need as much choke and seems to run smoother now. I'm still fooling with what seems to be too lean stock jetting. You're on the right track with your step by step troubleshooting and in the end w/ all the great help and your patience, you will have a great running bike and WE will all be alot smarter for it:laugh: Thx and keep it up.

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Jet needle improves acceleration. 20 Jul 2011 21:37 #464027

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Well it's definitely electrical!

I started at the solenoid and tested for voltage drops up through the switches and then down to the coils. I'm now getting 10.5 V with the new blade fuse installed.

I finally picked up 12.5 volts to the coils only after unplugging the red lead from the dyna s ignition where it taps onto the oe ignition circuit.

Not sure where to go from here?
1976 Kz900 A4

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Jet needle improves acceleration. 20 Jul 2011 22:03 #464032

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Not sure about that. I have the factory inductive pickup. Like I said earlier, are you losing alot as it goes up thru the kill switch and then to the dyna unit? You can use the voltage coming from your kill switch to operate the new relay on it's way to feeding the + side of each coil.

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Jet needle improves acceleration. 20 Jul 2011 22:59 #464051

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All is good when the ignition module is unplugged. I cleaned and checked the ground. I also did the dyna s module check and got spark.

I'm thinking but, but very much stumped unless the module is in fact bad.
1976 Kz900 A4

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Jet needle improves acceleration. 20 Jul 2011 23:56 #464064

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I am also getting 12.5 V when I disconnect the short lead that splits to the coils and with the module plugged into the ignition circuit.

I'm getting a voltage drop when the circuit is a closed loop but not when it's open ended?
1976 Kz900 A4

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Jet needle improves acceleration. 21 Jul 2011 00:28 #464072

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calvin17d wrote: Well it's definitely electrical!

I started at the solenoid and tested for voltage drops up through the switches and then down to the coils. I'm now getting 10.5 V with the new blade fuse installed.

I finally picked up 12.5 volts to the coils only after unplugging the red lead from the dyna s ignition where it taps onto the oe ignition circuit.

Not sure where to go from here?


...finally picked up 12.5 volts to the coils only after unplugging the red lead from the dyna s ignition where it taps onto the oe ignition circuit....


If not already done, would assure that the Dyna coil terminal screw isn't shorting against the coil mounting spacer.

It should be okay for the Dyna-S red wire to be spliced into the red/yellow harness wire that feeds either or both ignition coils, and such splice connection should not cause any drop in voltage being furnished to the ignition coils.

Good Fortune! :)
1973 Z1
KZ900 LTD

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Jet needle improves acceleration. 21 Jul 2011 00:53 #464077

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calvin17d wrote: I am also getting 12.5 V when I disconnect the short lead that splits to the coils and with the module plugged into the ignition circuit.

I'm getting a voltage drop when the circuit is a closed loop but not when it's open ended?


I don't know how this system works exactly but if you break the Dyna side of the circuit does it fire the coils? if so maybe the breaker side has a short internally. which would account for your voltage drop. Have you performed a actual drop test inline? (postive to first connection all connections made, voltage there indicates actual voltage lost.) Example battery positive to positive side of coil, reading 2.0 volts = that amount of voltage drop. Go through each connection to connection and see where the most drop is. Hope this makes sense, and helps find the problem.
Kenny Hicks
74 Honda CB550
75 Honda CB360 (runs and rides good but not a show bike)
77 KZ650B1 (Runs Great, but needs painted and a little work.)

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Jet needle improves acceleration. 21 Jul 2011 00:55 #464078

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I suspected a short on these screws a few weeks back. I took care to file the head down and cover them with silicone. Why would they design it this way.

I can't say for certain without closer inspection of the lower screw. I did put the volt meter on the lower terminal after testing the primaries. The primaries read 10V and there was no reading on the lower terminal.

Is this correct reading for engine off ignition switch on.
1976 Kz900 A4

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Jet needle improves acceleration. 21 Jul 2011 01:13 #464081

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elfmagic17 wrote:

calvin17d wrote: I am also getting 12.5 V when I disconnect the short lead that splits to the coils and with the module plugged into the ignition circuit.

I'm getting a voltage drop when the circuit is a closed loop but not when it's open ended?


I don't know how this system works exactly but if you break the Dyna side of the circuit does it fire the coils? if so maybe the breaker side has a short internally. which would account for your voltage drop. Have you performed a actual drop test inline? (postive to first connection all connections made, voltage there indicates actual voltage lost.) Example battery positive to positive side of coil, reading 2.0 volts = that amount of voltage drop. Go through each connection to connection and see where the most drop is. Hope this makes sense, and helps find the problem.


Would like to be sure I'm understanding your questions. If I break the dyna side Aka module side do I fire Aka 12.5v at the coils?

Yes I do. But I also get 12.5v on the module if I remove the coils primary leads from the circuit.

The dyna instructions are very clear about not grounding the module to the frame? I'm not grounded to the frame from the module but isn't my case grounded to the frame?
1976 Kz900 A4

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Jet needle improves acceleration. 21 Jul 2011 02:37 #464082

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Here is a simmer case I found in PDF but i dont have archive access to read how it ended

kzrider.com/forum/4-electrical/54002-low-coil-voltage/fb_pdf
1976 Kz900 A4

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Jet needle improves acceleration. 21 Jul 2011 10:44 #464114

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In two of the similar posts I have found, there have been some explanations that seem applicable.
One of the individuals had been testing the circuit in the same manner that I was(pulling the connectors apart which reduced any load, and reading the battery voltage at that connection). This afternoon I am going to try the drop test throughout the closed cirtuit that reads 10V at the coils without removing or unplugging any of the components. I understand that this will pinpoint the area of voltage drop assuming that it is at a connection and not mid wire amidts insulation.

Will post results
1976 Kz900 A4

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