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76 KZ900 Plug Fouling 14 Nov 2022 12:15 #876829

  • mrmach5
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Pretty frustrating ,
76 KZ900  Mikuni VM26SS carbs.  This will be the third time the carbs have come off in an effort to correct the plug fouling issue.
I have made the Wired George relay modification to assure the coils are getting full voltage. New viton choke plunger seals . Currently has 15 pilots, and 115 mains . Needles are stock 5DL31 clip in the 3 slot. .Floats set at 22mm. With brand new ND W24ES-U plugs in , it will heavy soot foul the plugs within 30-45 minutes of riding. I've tried hotter heat ranges with no improvement.
???????????

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76 KZ900 Plug Fouling 14 Nov 2022 12:26 #876831

  • Warren3200gt
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Weak spark, 
Oil fouling, 
Rich mixture, 
Too cool plugs. 
Any one or combination of more than one will foul plugs. 

Z1000J2 somewhat modified!


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76 KZ900 Plug Fouling 14 Nov 2022 12:37 #876832

  • F64
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Is it fouling the same amount on all 4 plugs?
81-KZ440-D2.
Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY

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76 KZ900 Plug Fouling 14 Nov 2022 12:40 #876833

  • Nessism
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Header?  If so, what baffle?
Pods?  If so, what brand?  How long since last cleaning?
Points?  If so, condition?
Coils?  If NOT stock, which brand and type?

Have you checked spark by grounding a plug outside the engine?  Is it sharp and clear, or barely there?
Ed

Carburetor O-ring Kits For Sale: Mikuni VM & BS/CV, and Keihin CV34 (as used on KZ750E/H/N/Spectre, 400)

www.kzrider.com/forum/forum-index/faq-wi...owner-things-to-know

1981 KZ750E2
www.kzrider.com/forum/11-projects/604901...z750e-project-thread

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76 KZ900 Plug Fouling 14 Nov 2022 13:01 #876834

  • mrmach5
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Yes. all four plugs fouling , pretty much the same.

Stock airbox New filter
reproduction 4 into 4 exhaust
New Coils -strong spark
new points & condensers

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76 KZ900 Plug Fouling 14 Nov 2022 13:22 #876835

  • Wookie58
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Definite sounds like it's over fuelling or not getting a full burn
  • Is the ignition timing correct
  • Is the cam timing correct
  • What are the compressions like
  • Does it "rev out" (possible poor exhaust flow)
Any of the above will cause a "poor burn" of the intake charge
1982 KZ1000 Ltd

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76 KZ900 Plug Fouling 14 Nov 2022 13:32 #876836

  • F64
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Is this the same bike/problem you had July 12 2020?
81-KZ440-D2.
Louis Dudzik's GM HEI ignitor conversion installed 2015 s3.amazonaws.com/gpzweb/Ignition/GPZgmHEImod.html
Motogadget m-unit blue installed 2017.
LIC, NY

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76 KZ900 Plug Fouling 14 Nov 2022 13:36 #876837

  • Mikaw
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Need to check float levels with the clear tube method. Measuring is just to get you close. 
1976 KZ 900 A4 kzrider.com/forum/11-projects/613548-1976-kz-900-a4
1976 KZ 900 B1 LTD
1978 KZ 1000 B2 LTD
1980 KZ 750 E1
Kowledge Speaks, But Wisdom Listens.
Jimi Hendrix.

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76 KZ900 Plug Fouling 14 Nov 2022 18:59 #876845

  • z1kzonly
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Tired, Original engine??
Did you do a Compression check?
Did you do a leak down test with real equipment?
I am done with my KZ stuff, but worked on an old friends KZ 900 this summer.
Did all the basic cleaning, adjusting, few new parts, basic stuff.
And the original pistons and rings were worn out, It needed a valve job and guides.
I told him so! He just kept hoping it would run better.
I got paid, 1/2 of what I should have charged him.
Glad it left my garage!!
Thing had low, uneven compression.
He almost passed out when I told him new pistons & boring - $800 - $1000?
Total head rebuild, valves, guides, springs $500-$600.
Gaskets $150.
To do it right!
Then Labor. 

I don't know your history of your cycle?

Good luck.
Livin in "CheektaVegas, NY
Went thru 25 of these in 40 yrs.
I SOLD OUT! THE KAW BARN IS EMPTY.
More room for The Old Girl, Harley 75 FLH Electra Glide,
Old faithful! Points ign. Bendix Orig. carb.
Starts everytime!

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76 KZ900 Plug Fouling 15 Nov 2022 07:04 #876857

  • mrmach5
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I said  new points and condensers , incorrect.
Bike has good compression, valves adjustment in spec. It has a Dyna S ignition and Dyna 3 ohm coils. Timing is dead on and the coils test out within spec. I replaced the exhaust with a new reproduction 4 into 4. Stock airbox with new stock paper filter, I've adjusted floats using the clear tube method. I've gone two heat ranges hotter on plugs with no real change.
At one point a while back I thought I was getting close to correcting the issue, but not so. One clue that might be telling is the excessive foulng seems to occur during long periods of part throttle , 30-40 minutes at 45-55 MPH ?

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76 KZ900 Plug Fouling 15 Nov 2022 07:28 #876858

  • Wookie58
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Just out of interest have you tried lowering the needles 1 groove to see what effect it has (I assume you don't have access to an exhaust gas analyser ?)
1982 KZ1000 Ltd

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76 KZ900 Plug Fouling 15 Nov 2022 07:51 #876859

  • mrmach5
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I guess I was thinking that would be my next move , that or move the main jet down to a 112.5 . Not sure which one would have larger effect ?

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