Topic: inconsistent idle

[Dakotarider]

Went for my first test ride on the 78 cb750 yesterday, after carbs rebuilt, balanced, and tuned.
It ran beautifully except...
The idle is erratic and doesn't respond normally to choke settings and idle screw changes.
When cold, the bike take about 10 kicks to go. One little kick when warm.
Turning the idle screw results in lower speed then 30 seconds later rev up again by 500 or more rpm.
Is this my choke messing with me?

Front wheel had a hop, but I need a new tire badly.
Shifting was hard, but I think cable adjustment should take care of that.  How my much play should be in the end of the lever?

[flybox1]

One kick when warm is normal.
10 kicks when cold is not bad, but certainly could be better.

PD carbs?
Plug caps - Checked for resistance and within limits?
timing and advance perfect?
idle plug chop to get A/F mixture correct?
Clear tube test to get proper fuel level in bowls?
Vacuum sync gauges.
repeat...

do you have dial, or liquid vacuum gauges?  If the dial type, did you calibrate them?

[Bankerdanny]

78 F or 78 K? Original carbs? Erratic idle can indicate a vacuum leak. When you out the carbs back on did you get the carbs fully seated in the rubbers? Are the clamps all properly tightened? Factory air box and filter or pods?

Why kick start? If you have the electric use it. It spins the engine much faster and longer than you can with the kicker and it will start easier.

Who did the carbs?

[Jimray23]

Have you done the clear tube test on the carbs to check float level?

--------------------------------------------------
Jim
1979 kz1000b ltd
    stage 3 cams
    pod air filters
    4-1 open exhaust(no muffler)
    full rewire
    dyna-s ignition
    dyna 3 ohm coils

[Dakotarider]

CB 750k with PD carbs, factory airbox, rubbers are good and all seated/tightened well.
I rebuilt the carbs.
Float levels between 2 and 4 mm below top of bowl using clear tube test.
Starter doesn't work yet. Solenoid just clicks once, it is sending juice.  Haven't messed with it yet.
timing perfect, advance rebuilt,
a couple of plug caps are broken but clamped well enough,
I've never performed a plug chop before, and never tested plug caps for resistance.

[Mr Freeze]

I'd check the resistance in the plug caps based on your info.

[Dakotarider]

what should the resistance be?

[flybox1]

If they are 5k ohm caps, any cap reading over 7kohms is going bad.
f-it.  get new caps.  might run you $10.  5k ohm caps will measure <5kohms.