Tweaking the carbs

Just picked up a 1980 KZ 1000 Ltd.I was able to get the plates squared away today and took her out for a test run.Had it out for about an hour or so.Bike started with one kick,battery needs to be replaced,when I picked it up prior owner said he charged the battery as the bike sat for a year or so,but when he hit the electric start it fired right up.So after it warmed up,it was idling a bit rough but nothing devastating.When I got back from the ride and turned in my driveway and stopped,the bike the engine was racing at about 3500 rpms,the throttle returned to the closed position,so I know its not the cable sticking.After a minute or so it slowly came down to about a little under 2000 rpms.Shut it down,restarted and it idled okay til I flipped the throttle and it stayed at about 4k for a few and then the same,wouldnt come down all the way.It ran well,plenty of power no hesitation,good response.Think it may just need to run itself "clean"?I would think dirt would have the opposite effect tho.I'm guessing the carbs need a thorough going over,but I dont have the means to sync them.Thoughts?

Fist thing is do a complete tune up including valve clearance checks, check the mechanical timing advancer, clean and synch carbs, at least bench synch them, new plugs, etc. Do not just try and diagnose a problem on a bike that it's condition is unknown. Start with a base line.

I plan to take it to a mechanic for all that.Although I am very mechanically inclined and have done work on various bikes over the years,I dont care to start tearing the bike down right now.But I gotta get it there.Dont want to have the throttle stuck at 4k or so at the wrong time.I took it for another test spin after it sat for an hour or more,and it worked ok this time,no over rev.I'm gonna call the wrench tomorrow and see when he can take it.Just figured I'd ask here and get some thoughts on this particular issue.

I'm not sure if you have a push- pull throttle set up but when I bought my 76 kz900 it was acting a lot likt this. It turned out it was the throttle cable that returns it to no throttle. When I went to pull the carbs off something didn't feel right. I was detaching the throttle cables so I pulled them by the end and the cable totally separated and pulled apart. If you're gonna pulll off the carbs you're gonna have to detach the throttle cable anyway so you should check out the condition of it at the same time.
and then do a tune up, and don't forget to check the clutch cable too! it sucks trying to limp home while not using the clutch!

when mine was doing this it felt like the throttle was closing but the cable was separated inside the sheath so it really wasn't.

Thanks,KZ802,I was just looking at the service manual and was thinking just that.I'm gonna pull the tank tomorrow and give the cable a good going over.Looking under the tank from the side it appears the cable bracket and stopper are making contact,leading me to think the return was fine,could be as you describe.I did lube the clutch cable today,as the clutch was real stiff,hard to squeeze.Was gonna lube the throttle cables tomorrow anyways,so I'll check that return cable,it sounds like that could be the problem

So I took the tank off and checked the cables they looked ok.I lubed them up and tried adjusting them as per the manual.It says to loosen both cables at the upper adjusts at the grip.Then it says to adjust the decelerator cable til there is no clearance between the cable bracket and the stopper,there was about 1/8" clearance when I began.Well,no matter how I adjusted the cable I could not get the clearance out,or make the clearance wider.After an hour adjusting both ends of the cable with no luck,I realized the clearance was being caused by the idle adj screw.There was no mention of the idle adj in the instructions at all.So I adjusted both cables as best I could and took it for a ride.It functioned better today,no sticking on decel,but it does come down a little slow when I rev it in neutral.It idles a bit rough and probably needs a full tune up,as suggested earlier by Baldy 110.I assume this bike still has the old points,who makes an electronic ignition to replace the points?

I have a Dyna S. You can get one at Z1E or other places.
Steve

The points ignition works quite well when properly cared for. Points and condensers are much cheaper than a whole new system. If you are going to replace, be sure to replace those old coils, too.

YUP.
Steve

Thanks for the replies,guys.I'll probably stick with the points,cond for now.The bikes gonna need a complete tune-up,carbs synced,valves shimmed etc.I 'm gonna let a mechanic do it all this time,I want to ride this bike NOW,dont wanna spend a lot of time getting it in shape.I'll look into the elect.ign later.The brakes are good,but that I can do easily,I can hear the timing chain rattling some,thats an easy adj. but I'll have the wrench do that while he's tuning it up.