Run away RPM's

i had a prob kinda like that with my 1979 kz1000 i cleaned the carbs i removed the carb boots and resealed them , was still the same . then i took the tank off and had a good look at the linkage , and i noticed that when i turned the thottle the spindle that runs tho all four the carbs , didnt move with the thottle maybe like 2mm of play on it ,i tightend up the bolt on the part the cables run in on the linkage and sorted the problem .. took me a while to work out what my prob was lol .. not saying thats your problem but its a simple thing to check ..

Check the timing advancer, the return springs get old and weak or the advancer is gummed up not allowing the timing to return. I had the exact symptoms on my GPz1100 and it was the advancer springs, they looked and seemed to operate fine when I checked them by hand but I ended up cutting a winding off each spring to make them shorter this fixed the problem.

I'm having a very similar problem on my 79 kz400. The engine will stick at around 3000rpm when the throttle is rolled off, but I am not able to force the throttle forward any to rev it down. When it sticks, the only way to bring the rpms down is to engage the clutch.

Thanks for all the suggestions. This thing is driving me nuts! Checked the timing advance and lubed, it's working perfect. Think I've had these damn carbs off five times now. When the bike is off the slides operate smoothly and close very easily but I did notice that when it's running there seems to be a spot that something is "catching" just before they close completely. Looks like I'll be pulling them off again tonight to see what that's all about.

Like I said the timing advancer will look and feel normal. I would still cut a coil off the springs at least to elimnate them as the problem.

baldy110 what did you use to lube the advancer im having the same issue

is this bike have points or electronic ignition??? if it has points it sounds similar to my 76 900ltd when i first got it.. had the same problem with engine idle and revving way up just like your describing.. as a last resort i checked the points gap and they were almost completely shut,, once i got the points cleaned and regapped the bike idled and run perfect.. would have bet money it was in the carbs but it was point gap...

Had a similar problem after using Motorex Joker440 synthetic spray lube while re-assembling carbs. Sprayed the cables and twistgrip barrel as well as carb linkages. Very tacky product and stayed incredibly thick. Almost grease-like. Cleaned it all out and re-lubed with silicone and problem disappeared.