kz 440 hesitation/83, ltd

just cleaned the carbs and put them back on ...this bike was siting for 14 years and only has 1400 miles on it...now it starts and will run , but hesitats at mid throtle and needs a little choke...it will idle fine once it warms up, but there is something causing the mid range power loss...im thinking the diaframs may be leaking as they are so old (1983)....but the look fine...no visable tears...but may be dry rotted...any suggestions how to get the bike up to specs? thanks in advance....

One thing you will want to check is if you have your air cleaner mounted correctly. I know this sounds silly but there was a Tech bulletin out on it back when these were new. To check it try lifting up on the rear of the filter if it moves up it is mounted wrong. There is a sort of lip at the bottom that has to fit down into the the airbox before you install the two screws on the top. If this is mounted wrong it will cause hesitation.

check that the ignition advance unit is moving. if it runs well enough, try to put a few miles on it and see if it improves. all my 400 act funny in the spring till i start driving them more often

Are you happy that it's not ignition related ? You did put new plugs in right ? not 14 year old ones :laugh:
.... or that it's not a stuck timing advancer ?

If you cant see any pinholes in the diaphragms and if the rubber is pliable and feels ok then probably not that.

I think your carbs are Keihins. Can you confirm. When you cleaned the carbs did you remove all the jets, poke through the holes with something like a bristle from brush, spray carb cleaner down evey hole you could find and finally blow out with compressed air ?

What I'm thinking, if it is indeed carb related , is blocked transition holes. I also have Keihin carbs and mine used to stumble at about 3,500 rpm when I got it first. Above and below that # it was just fine. It took me an entire summer to find the little b*ggers. Look into that part of the carb which connects to the engine. Raise the throttle flap and just behind the flap is a grouping of 3 tiny holes. I used some very fine wire bent at a right angle to poke through and followed with a liberal spray of carb cleaner and compressed air. Once the transitions were clear then no more stumble.

Also worth following The Gringo's suggestion.

Check the photo below

Good luck and let us know how it works out