Carb Issue?

Hey everyone, i have a 1979 kz650. It has a big bore kit, electronic igniton and aftermarket exhaust. Lately i have been having fuel issues. The carbs are clean, not sure if they need a rebuild or if new carbs can be obtained. But when i get to around 4000 rpm the fuel likes to stay on even when i am off the throttle. I greased the cable and it did not fix the problem. When i used the mercury sticks the it was fixed for about a hour and half of riding till it reacurred. Any ideas? I was thinking the carbs were just worn. If this is the case would a rebuild fix the problem? Or is there somewhere i can obtain new carbs, as with the big bore it is probably a good idea anyway. Offhand i cant remember the bore size if needed i will look into it been about 2 years since i did that .

welcome, have you removed the cables and worked the throttle by hand? , also check to make sure the cables are not in a bind enroute to the carbs, and last look for a poss vacum leak

Thank u i will check. The vac. leak is quite possible since i did the mercury sticks:) and who knows, the cables could be stuck inside, grim since 1979 has got to be hard to get rid of no mater how hard i try lol. I will get back to u with diagnosis asap.

slides could also be sticking. if the revs come down slowly most likely a vaccum leak.

Turned out to be a vac. leak! Thank you both. Running like a raped ape again!:woohoo: