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Idling issues
- SeattleKZ
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The one problem that I can't seem to sort out is the idling. I have to turn the idle adjustment up when it's cold and then down when it's warmed up. Then if I rev it, the idle will stay up around 2500 rpms for awhile and then slowly drop down and almost go so low it dies. If I just let it idle on it's own the idle fluctuates between 1200-2500 rpms. I know this can be casused by a vacuum leak, that's why I changed the intake manifolds, but that didn't seem to help. Can and air leak be coming from somewhere else?
What else could cause this?
Also, when I synced the carbs the vacuum strength seemed lower than bikes I have synced in the past.
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- Patton
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May use a drop of motor oil on each of the two pivots.
May access the pivots via the timing inspection window.
Inspect the weight arm springs on the timing advancer to assure that the weight arms are consistently being freely pulled back to their fully closed position.
The advancer isn't supposed to look like this:
Erratic idle may also be caused by conditions other than an issue with the advancer.
If not already done, would check the valve clearances and assure they are within specs, because too tight valve clearances may contribute to the reported issues.
To test for air leak at carb holders, or a loose clamp, may spray WD40 about the carb holders and watch for smoke from the exhaust which would indicate ingestion of the WD40 into the intake tract. May also notice a change in the idle rpm caused by ingestion of the WD40.
Good Fortune!
1973 Z1
KZ900 LTD
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- Patton
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Has there been any popping from the exhaust on deceleration?
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1973 Z1
KZ900 LTD
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- Patton
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And maybe the throttle cables need lubing.
There's of course the time-honored "still dirty pilot circuits" possibility.
Good Fortune!
1973 Z1
KZ900 LTD
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- SeattleKZ
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- SeattleKZ
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- Patton
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SeattleKZ wrote: I started with the idle jet screws 1.5 turns out from gently seated and as I tuned the bike and checked the plugs I ended up turning them back in 3/4 of a turn. The screws and now 3/4 out from being seated. That has helped with throttle response but not the idling issue.
Seems excessively rich.
Does tuning the pilot air screw make a noticable difference in idle rpm?
If not, would suspect an imperfectly clean pilot circuit.
Would inspect the pilot screw tips, which might be damaged and thereby failing to properly regulate air flow into the pilot circuit.
Would also assure that the o'rings on the pilot screws are in good condition so as not to allow air leakage.
Good Fortune!
1973 Z1
KZ900 LTD
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- SeattleKZ
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- Patton
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For example, the popular Dyna-S retains and requires the stock timing advancer.
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1973 Z1
KZ900 LTD
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- SeattleKZ
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- Patton
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Patton wrote: Another possible issue could be adjustments of the throttle cables, which might lack sufficient slack, or be hanging (for whatever reason).
And maybe the throttle cables need lubing....
When gently closing the throttle, should hear a faint but definite click from the carb as the throttle stop makes contact with the end of the throttle adjustment screw.
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1973 Z1
KZ900 LTD
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- Patton
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Same applies when performing a running sync.
Good Fortune!
1973 Z1
KZ900 LTD
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