Factory plug and boot resistance

  • GrumpierGrunt
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Factory plug and boot resistance

26 Sep 2024 07:45
#904628
Hi everyone! I am working on a ‘85 Kawasaki 750 Turbo that won’t idle, it’ll start and run for a couple seconds but then die out. Progressive attempts to start the bike result it in not running at all. Seems to only run with the starter button engaged. I have no throttle response and throttle has no effect. 

This was a project that was supposed to be limited to a quick cosmetic upgrade that quickly evolved into a engine out project, not for mechanical reasons but because I wanted to powder coat the frame and other bits. 

I’m ready to fire the parts cannon, but started to focus on anything and everything I might have changed. One item I changed were the coils. I should have left the dyna coils on, but was able to get a set of NOS coils for free from a friend. I picked up stock boots as well and a set of plugs (BR9ES).

I wonder if my issue is related to too much resistance in the boot, as it is a stock resistor type, coupled with the resistor in the plugs. I am not sure what type of wires came stick with this bike, but why would Kawasaki from the factory recommend resistor plugs and resistor caps?

it seems to be a big no-no from what I’ve read. 
 

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  • Wookie58
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Re: Factory plug and boot resistance

26 Sep 2024 07:50
#904629
Resistor plugs and caps will give you a weak spark, I would suggest before you delve too deeply into the issue you have replace the plugs with "non-resistor" type and see how you go. If that doesn't sort it then I can help you with electrical testing of the fuel and ignition system

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  • SWest
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Re: Factory plug and boot resistance

26 Sep 2024 08:09
#904630
And put the dyna coils back on. What color are they?

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  • GrumpierGrunt
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Re: Factory plug and boot resistance

26 Sep 2024 11:00
#904634
Thanks everyone!

The coils preciously on the bike were gray dyna coils. 

I forgot to mention that I’ve tested ECU, fuel pump relay, and IC igniter on a working bike and they were fine. Also, I’ve done the tests per the supplemental manual and they’ve checked out fine. Computer is throwing no codes and TPS is responsive. 

i tested the magnetic ignition pickups and the resistance was within spec and the coil primaries seemed fine. I used a heat gun to test the pickups but not the coils, so I might check that.

also, I tested compression and it was okay-ish. 145/145/145 and 120. C4 seemed low as Kawasaki says that any cylinder with a 14 psi difference is suspect, but I think it’ll come around with proper running.

it shouldn’t cause the problem I’m currently experiencing.

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  • GrumpierGrunt
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Re: Factory plug and boot resistance

26 Mar 2025 19:16
#910592
     

Could this be the source of my frustration? There’s like negative gap with the left pickup coil magnet and it’s been gouging it out, leaving metal shavings on the right magnet. 

bike is missing on 2/3, causing rough idle and stalling. No throttle response either.

I have spark but the pipes are cool to the touch while 1/4 are scorching. Spark looked a little funny though, like off in color. Plugs on 2/3 were wet and sooty. 

 

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  • Scirocco
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Re: Factory plug and boot resistance

26 Mar 2025 19:52 - 26 Mar 2025 20:13
#910593
As far as i can see on the first view in your pics, the rotor grinded into one of the pic-ups ferrit cores (scar marks)!
Could be a woobling rotor or dis-alignment pic-up postion on the mounting plate.
Grinded metal flakes on the, (catch up by the magnetic pic-ups), can disturb the firing timing.
On modern engines it´s a common problem with the crank OT sensor unit on the clutch flywheel gearbox housing side .
You get no ingnition release signal from the ECU on e-start 
Just my first thoughts due to your pics.......
Last edit: 26 Mar 2025 20:13 by Scirocco.

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  • Wookie58
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Re: Factory plug and boot resistance

27 Mar 2025 00:14
#910599
It certainly isn't helping - there should be no physical contact with this type of sensor !!

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  • rangeroy
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Re: Factory plug and boot resistance

27 Mar 2025 02:41
#910600
I'm with wookie on this, resistor plug caps & plugs not a good mix, try pulling caps off plugs so spark has to jump across a little & again that ignition rotor should not be touching anything as it spins, good luck hope it works out 
1977 z650
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