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Missfiring cylinder, Is it my carbs??
- 88alltrac
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This problem happens at idle and while driving.
So I have cleaned the carbs twice, the second time I pulled them off the rack and dipped them and everything.
I just replaced the carb holders and the boots between carb and airbox.
New spark plugs, gapped to spec.
New plug wires.
Wired georges coil mod.
Fully charged battery.
Ignition timing is right on spec.
Compression is in spec on all 4 cylinders
When I switch 1 and 4 plug wires the problem stays on cylinder #4.
I have bench synched the carbs and then vacuum synched them.
I have set the fuel levels with the clear tube method. I have gone slightly higher and slightly lower on the levels as well with no luck.
So switching the plug wires with no change should rule out ignition. Compression is good. So the only thing left should be carbs right?
What am I missing? I am really sure I cleaned the carbs well.
81 KZ1000 K1
Lincoln NE
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- 88alltrac
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How sensitive are the fuel levels? I have had them anywhere between 1/16" to maybe 3/16" below the top of the carb bowl with maybe 1/16" difference between any of them.
I also checked all the valve clearances and they where ok. but i guess the good compression probably gives that away.
81 KZ1000 K1
Lincoln NE
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- Patton
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Is supposed to be a fat blue spark.
Also, please describe visual appearance of the old misfiring #4 spark plug. Am guessing black and sooty, but confirmation might be helpful. For example, a clean as-new appearance could indicate fuel starvation.
As known, adequate compression plus good properly timed spark plus correct fuel mixture virtually guarantees combustion. So it's a matter of zeroing in on the deficient leg of this trio.
My first guess was floatbowl fuel level being too high, but that seems to have already been addressed.
Good Luck!
1973 Z1
KZ900 LTD
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- Patton
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However, it should perhaps be noted that acceptable cold compression psi figures do not necessarily indicate proper valve clearances. This is because too tight valves may barely seat when cold (allowing compression) and begin leaking (failing to fully seat) as the engine reaches normal operating temperature.
Good Luck!
1973 Z1
KZ900 LTD
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- 88alltrac
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81 KZ1000 K1
Lincoln NE
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- 88alltrac
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81 KZ1000 K1
Lincoln NE
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- Patton
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Clear tube method is best for checking floatbowl fuel levels regardless of whether carbs are on the bike or on the bench. So long as the carbs are held steady and level during the process.
Would try to positively rule out compression and spark before further addressing carbs.
Good Luck!
1973 Z1
KZ900 LTD
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- 88alltrac
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81 KZ1000 K1
Lincoln NE
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- 88alltrac
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do i have to have one resistor in there or is that only if i am worried about noise on radios and stuff.
81 KZ1000 K1
Lincoln NE
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- Patton
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is there anything wrong with me running the non suppression core plug wires, no resistor caps and the non resistor ngk's.
do i have to have one resistor in there or is that only if i am worried about noise on radios and stuff.
I run both Z1 and KZ900 the same way.
1973 Z1
KZ900 LTD
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- 88alltrac
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sigh. i guess i should look for a manual petcock. i just put new gaskets and stuff in the petcock not long ago and it still doesnt shut off. it is the vacuum type
81 KZ1000 K1
Lincoln NE
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- 88alltrac
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81 KZ1000 K1
Lincoln NE
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