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77 KZ 750 B
- Patton
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Voltage is 13 at the battery, 13 at the fuse, 13 at the connector in the head light, and 11.5 at the ignition switch and kill switch. None of the wires or connectors are corroded. They are like brand new?.....
If not already done, would study the wiring diagram, especially the connections inside the ignition switch and kill (on-off) switch.
To access on-site wiring diagram, click here > kzrider.com/index.php?option=com_docman&...d&gid=282&Itemid=108
Voltage enters ignition switch and exits to kill switch where it exits to ignition coils
With 13 vdc going into ignition switch, is supposed to be 13 vdc exiting and going into the kill switch, with the same 13 vdc exiting the kill switch and going to the coils.
Perhaps losing voltage in ignition switch and/or kill switch.
Such voltage loss might result from corrosion inside the ignition switch (or maybe the kill switch).
Good Fortune!
1973 Z1
KZ900 LTD
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- bgulsvig
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- Capt America
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Air mixture screw for the idle circuit is "what it does" and if turning them in or out is having no effect and you have soiled black plugs from excessive fuel, it is definitely a problem you'll need to correct.
Best of Luck.
Capt A merica
1983 K1 750 twin
Ontario, Canada.
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- bgulsvig
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The last time installing them a found a small slit on the seam of one of the rubber air ducts running to the air box. Could that small slit make it run rough at speed but idle fine?....
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- Capt America
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I'm still a bit baffled by the air screws having no effect, if you cleaned carbs and inspected diaphragms. Even with open carbs (some effect), or pods on (more effect), or a leaky box (better effect)... the air screws should still have an effect, in my experience.
You could, for a test at least, set the air screws to stock staring point and tape up that boot good with some duct tape or electrical etc... should be able to get a good enough seal to determine if that is causing all the ruckus.. if so start looking for replacements. If one is shot most likely the other is near it's end as well. (Filter is in and cap on air box of course.)
More questions for ya, sorry heh:
Do you have the needles on the 4th notch down from the top???
With the carbs all buttoned up before you put them back on the bike, when you lift the slider up to the top with your finger and plug off the vent with your other thumb, how long does it take your sliders to fall to seated?? It should be about 10 seconds, and they should be fairly even.
If you didn't do that test, you could undo the 2 bolts holding the air box to the frame and should be able to push it back enough to get velocity stacks off carbs and spin them out of the way to do the above test. Sometimes a visual inspection of diaphragms won't expose pinholes.
When you did your kit in the carb, you didn't by chance forget the part # 37 in diagram did you? tinyurl.com/242849c
Capt A merica
1983 K1 750 twin
Ontario, Canada.
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- bgulsvig
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- Becker
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- The Doctor Will Rise Again
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You still haven't talked about how you fixed the low voltage at the coils.
If the voltage is lower then 12.65 vdc at the coils then it is to low. Alot of people are against the WG coil mod here and for goood reason. But it is a cheap and easy diagnostic tool.
If you follow their advice and still get more then 12 volts at the coil then you'll be fine but according to the last time you posted you only have 10 volts. That isn't enough. You need 12.65 VDC at the coils to be within factory specs. 12.80 would be best. I still think it is an electrical problem since you are reporting sooty plugs and low numbers at the coils. This bike will start under stupid bad battery conditions and run all day. I know. My bike drove 300 miles with a bad battery last year.
But if your switches are corroded and shot then you won't be able to produce enough voltage to clean the carbon off your spark plugs. They'll look sooty and act like the carbs are rich.
You need 12.65 volts at your coils. For older bikes like ours it may not be as important but in the shop I work I'll tell you right now when a bike comes in with an electrical problem we imediatly check battery voltage and if it isn't up to snuff we won't even test anything else.
BTW 12.65 is normal Battery voltage.
I will admit that the BS 38 carbs are a whole nother animal to diagnose. But they follow normal carb tuning rules. Except jets can leak through the float bowl gasket and that is why the are a pain.
78 KZ750B3
79 KZ400 LTD
78 KZ650C2
79 KZ650C3
78 KZ650B2A
80 KZ650F1
80 KZ650E1
81 CB750K Super Sport
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- bgulsvig
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- In-line fuel filters
- Coil/relay mod
- New coil, wires, caps, plugs
- Carb kit in both carbs
Idles fine but still cuts out or stalls when I try to ride it. I pull the plugs and they are black. Should I be using B8ES or B6ES plugs.
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- bgulsvig
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- bountyhunter
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It's not normal. If the pilot circuits are functioning at all, it's not even POSSIBLE. Your carbs are really screwed up if they do that. You need to fix the fuel system before screwing with the coils. The basic fuel system cleanup:bgulsvig wrote: I was tinkering with it last night and tried to adjust the carbs. I let it idle for a full ten minutes. During that time I tried different settings of the pilot screws. At one point I had them both screwed all the way in and seated. There was no change in idle speed. Is this normal?
1) Clean fuel tank, remove rust
2) Clean petcock/screen assembly
3) Install inline filters
4) Set fuel levels in bowls with clear tube
5) sync carbs
6) Check intake manifolds for leaks
7) Check diaphragms CAREFULLY for tears or slits
Clean carbs, clear jets and all passages
IMHO, 10 - 11V at the coil terminal is plenty to run the coil. The system is designed to tolerate some voltage drops. Obviously no voltage loss is ideal, but if the engine starts OK, you are getting enough voltage to run. The battery drops an additional 3-4V when cranking the starter, reducing coil voltage to minimum. If it starts, it should run fairly well.
1979 KZ-750 Twin
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- bgulsvig
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- bountyhunter
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The pilot circuit feeds the engine at idle and small throttle openings maybe up to 1/4 throttle.bgulsvig wrote: I have done all of the items except 4 and 5. What is involved in syncing the carbs? Also what does the pilot circuit do anyway?
Syncing means making sure the carb throttle butterfly plates are open the same physical distance at idle so they will be balanced. You loosen the clamp between the throttle shafts to adjust this.
1979 KZ-750 Twin
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