High Revs after getting on throttle

1980 kz750h1 starts and idles fine, when I go to ride and get on the throttle it revs high when I get off throttle and down shift. It settles down when I up shift.

Possible vacuum leak, probably rubber manifold, and heat related.

You should also go thru and check other maintenance related items, valve lash, and ignition timing at the very least.

This could also be a carb issue, fuel level, etc. - really need more tuning info to properly assess.

In addition to the above I would add checking the clutch adjustment.

Sounds like a vacuum leak.  Remover carbs and boots, and flex boots while looking close under a mag light.  

Carb sync can also have an effect,

I will doing a carb sync again tomorrow, I tries today and vacuum was only at 10 on all 4 carbs. I did not clp either end of rubber hoses. I have a Vand H 4 to 1 and uni pods and stage 3 6 sigma kit. I took it for a spin and checked plugs, 1&2 were white and 3&4 were black
 

So I synced the carbs and I get 10psi on all 4 but once I blip the throttle it high revs and won't come back down to idle. So I took valve cover back off and now I am real tight on cylinder 1 exhaust and intake,close on the rest.but I don't believe that is the problem. Coil pick up test with spark plug failed, could that be the problem?


Thanks Kane

So I put new 3 ohm oem coils and plug wires on and adjusted the clutch ber spec. Still high revs after warmed up as I slow down and stop. She idles fine and runs fine bit revs at 6k and don't settle down. More noise from clutch or starter since I adjusted clutch cable. Any ideas would be appreciated.  Thank you  Kane

Have you tried disconnecting the cable from the carbs and operating the throttle manually ?

I have not tried that, it's a new cable and snaps back nicely.  It does not do it when I just blip the throttle, but after I ride it and warmed up and getting on it. Could it be from running lean to cause that? Will try to get a video up. 

kanexx wrote:

I have not tried that, it's a new cable and snaps back nicely.  It does not do it when I just blip the throttle, but after I ride it and warmed up and getting on it. Could it be from running lean to cause that? Will try to get a video up. 

To "the best of my knowledge" hanging revs can only be either a mechanical issue not letting the throttle close fully or "unmetered air" (air leaks)

Hi.

This is almost certainly alean issue.  If the carbs are CV's check that none of the slides are sticking, Check all the carbs are closing by looking in the throats.  Open the trottle hard and check.  I'm suspicious about the new cable.  How new?  Like shortly before the trouble started?

Check the boots, and their seal to the head.  Are the boots old and hard?  Check the gaskets under the carb tops.  Feel around while it's idling after it's warm for any sucking.  Thankfully, there are only so many places a KZ can have a vacuum leak.

Make sure You leave a bit of freeplay in cable. Never mentioned if turning handlebar makes a difference? The CV slides wouldn't have any effect on a hanging idle but worthy of checking for general purposes. Your concern should be focused on the butterflies and their "individual" operation. Have You had these completely apart, separated off of rails? Only takes one carb that is not returning to exhibit this behavior.