Hanging idle cured!

Kept looking for vacuum leaks, bought new boots, pressure tested thru sync nipples, still hanging. Turns out it NEEDS the return cable. Mine didn't have one, but it did have a really strong return spring and you could hear the throttles snap closed. I always thought the return cable was more of a safety device. But while it was running, and hanging, I reached down and pushed the carb linkage closed and it dropped down to idle. My 1980 KZ1000 Classic actually had a screw plug in the control that I had to soak and use my hammer impact tool to finally get out. I had an older Honda return cable i was saving for a spare that fit close enough. I was then able to lengthen the return spring a little so it was easier to make the motor louder......
Also, I tried "Blue Job" to remove exhaust pipe blueing and had excellent results. Look for my post. I'll put a b4 and after pic.

Are these stock carbs?
And on what model?

Perhaps carb sync is needed.

Perhaps one of the throttle slides isn't fully closing, and the audible click is from the others that are fully closing.

Good Fortune!

The FI was replaced with VM28SS long ago. The sync was a little off when I checked it with the drill stem method. I fixed that and also #2 fuel level was a little high, fixed that. Gotta love the clear tube method for checking levels! But if it was just one carb hitting idle below the others, the idle would never come down. It's running great, just waiting on a shim tool to get a couple of tight intake valves adjusted. Thanks.

rekit wrote: ...still hanging. Turns out it NEEDS the return cable. Mine didn't have one, but it did have a really strong return spring and you could hear the throttles snap closed. I always thought the return cable was more of a safety device. But while it was running, and hanging, I reached down and pushed the carb linkage closed and it dropped down to idle.

Something is wrong, because the return spring on these carbs should fully close the slides without needing any assistance from a second cable or finger-pushing.
And the return spring on these carbs should fully close the slides without needing any cable at all.

The bench-synch (with drill bit or whatever) simply equalizes slide height to facilitate the later engine-running sync which equalizes cylinder performance at idle rpm, and usually results in changing the slide heights whereby the slide heights are no longer exactly equal.

The throttle mechanism likely includes a stopper on the pulley which is supposed to stop 1.6~2.0 mm away from the cable bracket when the carb is closed normally by the return spring.
Am thinking there's another short spring that allows further carb closing with manual force applied via the second cable or finger pressure, whereby the 1.6~2.0 mm gap may be closed.
Am guessing that such "super-closure" may allow an otherwise not-quite-closing slide to then fully close.

I believe the main purpose of such arrangement is to help prevent excessive pressure from being routinely applied by closing with the second cable, which excessive pressure might pull off a cable end ferrule.

Good Fortune!

yea, it seems like the vacuum won't let em snap closed. I was watching it w/o the return cable and when you let off it looks like it closes all the way but then you see the pulley close a fraction more on its own. It's only 1/16" or so and then it hits the idle stop. It is something I haven't seen before in many years of working on motors. But I think it rules out vacuum leaks since it does drop when the throttle is closed, however it happens. Running a tank of fresh gas with Seafoam mixture, hoping for the best. Can't do much else till I get the valves set.

rekit wrote: yea, it seems like the vacuum won't let em snap closed. I was watching it w/o the return cable and when you let off it looks like it closes all the way but then you see the pulley close a fraction more on its own. It's only 1/16" or so and then it hits the idle stop. It is something I haven't seen before in many years of working on motors. But I think it rules out vacuum leaks since it does drop when the throttle is closed, however it happens. Running a tank of fresh gas with Seafoam mixture, hoping for the best. Can't do much else till I get the valves set.

...watching it w/o the return cable and when you let off it looks like it closes all the way but then you see the pulley close a fraction more on its own. It's only 1/16" or so and then it hits the idle stop... -- Perhaps some mechanical interference in the throttle mechanism or perhaps a sticking throttle slide due to wear or dirt or oil or some assembly issue. Any of which could momentarily delay contact with the idle stop where only the return spring is relied on to close the throttle slides.

Am thinking the culprit here isn't related to vacuum, valve lash or needing Seafoam.

Good Fortune!

Hi, I had a similar problem just a few years ago. Went through everything like you did. Finnally found the problem was a loose linkage screw which had backed out just enough to prevent it's carb from closing. The yellow factory locktite lost it's grip I guess. All the rest were tight. Problem solved. Good luck
Joe