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TOPIC: Black sooty plugs

Black sooty plugs 02 Jul 2020 20:10 #829661

  • jamesjc1200
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Ok guys I'm back with another question. Kz650 runs good and sounds healthy but after a few long rides a few of the plugs are black sooty like it's either a ignition issue or to much fuel. I have 105 main jets with I think stock pilot jets and unknown needle jet setting, I'm running a modified exhaust and pod filters. This engine is on a quad frame and sees a lot of high RPM and I think I'm going through to many plugs as I've bought all the stores out in my area of br7's I have some denso equivalent ordered but unknown Time of arrival. I'm using Walmart supertech full synthetic 10w 40 four stroke oil because of its availability and it's smokes. Could the black plugs and smoke be because of the synthetic oil I'm using? I'm thinking about switching to a heavier weight and different brand but what you guys think? I just need this motor to last the season then it's time to rebuild or re ring in the winter
1977 KZ650B

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Black sooty plugs 02 Jul 2020 20:32 #829664

  • 650ed
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It may not help, but BR7 plugs are resistor plugs. That is not what the manual calls for. Try either NGK B7ES or better yet try ND (Nippon Denso) W22ES-U. At least that's where I would start. Synthetic oil won't make the engine smoke. I've used a couple different JASO-MA approved synthetic oils with no problem. I wouldn't switch to heavier oil. Ed
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)
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Black sooty plugs 02 Jul 2020 20:54 #829667

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I never thought it would make a difference. I know the resistor cuts out electrostatic interference but I just read that they also provide a sharper "edge" to the voltage spike making for a stronger, shorter spark. On high RPM motors it is important I guess.
1977 KZ650B

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Black sooty plugs 06 Jul 2020 17:22 #829977

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I think i found my problem as one coil just failed. My question is can i use OEM type coils with the dyna- s electronic ignition? I'm planning ordering one this week and 2 new coils but don't want to spend a whole lot on coils right now.
1977 KZ650B

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Black sooty plugs 06 Jul 2020 17:53 #829978

  • Mikaw
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Yes any coil at least 3 ohms

1976 KZ 900 A4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.
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Black sooty plugs 06 Jul 2020 18:02 #829979

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awesome! thank you for your response. i cannot wait to get rid of the old points and condensers
1977 KZ650B

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Black sooty plugs 07 Jul 2020 08:31 #830006

  • F64
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Remember, when you check your plugs. Their condition is dependent on when you shut your ignition off. If you shut off the ignition during idle, your idle mixture will be reflected in the plug's coloration. If you shut the ignition off at wide open throttle, then the coloration will be for that circuit.
81-KZ440-D2. Louis Dudzik's GM HEI ignition module converted 2015--no issues, Motogadget m-unit blue.
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Black sooty plugs 14 Jul 2020 18:09 #830680

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Wow i never thought of that, thank you for your input. I just changed both coils and they were both cracked so i'm thinking a new ignition setup will fix my issues. i will be installing the electronic ignition tonight as a did the coils last night. Will keep updated when i get it timed in correctly.
1977 KZ650B

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Black sooty plugs 02 Aug 2020 16:17 #832122

  • leadbelly
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Had same problem after rebuilding carbs and installing new dyna ignition with no luck I went back thinking it was carb related..wasn't...go to wiredgorge carburetors..tech tips it's from old wiring..either replace all of it or bypass wire harness with a circuit breaker ..he gives instructions
.runs like a champ now
Journeyman Machinist v twin expert ,,inline 4 rookie
76 Kawasaki kz 900
1200 cc

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