KZ650 will not idle after cylinder head change

I replaced the cylinder head on my 1977 KZ650 because of a small crack in the old head. The bike ran fine just had an annoying oil leak at the crack. I understand these motors very well and have spent considerable time working on these but now I am at a loss. I got the replacement head and replaced the valve seals. Springs, tappets, shims were all good. It has a Dyna electronic ignition. I checked the valve lash and after a couple adjustments it is in tolerance. Put the motor all back together, shot some starting fluid in the carbs and it started. I would have to keep on the throttle to keep it running as it would not idle on its own. I adjusted the throttle screw but all that would do is rev the motor and eventually it would die unless I keep on the throttle. I sprayed carb cleaner on the rubber carb holders but the RPMs did not change-no air leak?
I retimed the cams again this morning but have the same issue. When I do get it to sort of idle at 1500-2000rpms and rev the throttle the RPMs race way up 4000RPMs. I have to back the throttle screw way down to lower the RPMs.

What is puzzling is that it did not do this with the old head so I believe it is not the carburators. Most posts on this idle issue say, clean the carbs, make sure the cams are properly timed, check for air leaks, sync the carbs. As I said this was not an issue when the old head was on it so carburator problems , I believe, are not it.

Any ideas?

Sorry, I may not have read your post correctly, but are you attempting to use the carbs without synchronizing or adjusting them to the new head? :blink:

Sounds like an airleak. Spraying junk on the carbs only shows gross leaks, not small ones. The carbs could have gunked up while you did the other work too.

The carbs are in sync. As for adjusting them, there is only an air screw and that is backed out 1-1/2 turns as recommended.

Check the spark advance that it is not sticking.
Steve

I pulled the carbs and gave them a cleaning. Reinstalled and started it, It did idle better but started that high revving again. I checked the spark advance, moving freely. Added a little silicone on it. Started it again, same deal.
Interesting thing happened when I reinstalled the carbs, I forgot to connect the throttle cables and started it. It idled fine. Could the idle/high revving have anything to do with the throttle cables? Adjustment?

DOH!!!!

:woohoo:

Maybe i missed something here?
How are the carbs synch'd if you haven't yet got it to idle somewhat smoothly?
Did you bench sync them &/or vacuum gauge synch them?

Tadyccs wrote: The carbs are in sync. As for adjusting them, there is only an air screw and that is backed out 1-1/2 turns as recommended.

The carbs were bench sycn'd. The bike ran fine prior to the cylinder head replacement so I do suspect that the carbs are the issue.

You'll have to vacuum sync them to get a good idle.
Steve

I typed this wrong:

The carbs were bench sycn'd. The bike ran fine prior to the cylinder head replacement so I do suspect that the carbs are the issue.

I meant to type that I do not suspect that the carbs are the issue. There were 4000+ miles on that bike before the cylinder change and now the carburators are the problem? That does not seem logical.
It will idle ok now but a flick of the throttle and it races to 4000 rpms and does not back down.
What am I missing?