TOPIC:

After being told that my carbs were a lost cause, I rebuilt them myself (my first time) and the bike starts! (The bike has been out in the elements neglected for several years and is in real bad shape). However, the bike idles at approx 3500 - 4000 rpms and is unresponsive to throttle input. My push cable is broken, but I do not think its that because I can see the gizmo returning to the regular position when I let off the throttle. 3 Questions: Does anyone know a source for a push throttle cable? What is the typical Idle Speed for a 1976 KZ400? Any suggestions on why the engine is not responing? Any help will be greatly appreciated. I am a novice at this.

Mike

Taking on this project assures that you will not be a novice at this much longer...

On my 77 650 the cables are the same for push and pull.

I am curious what you did, or mean by "rebuilt the carbs."
I am also curious why you were told they were a "lost cause."

Having a bike in the elements,... gizmo (carb throttle linkage I imagine if it is the gizmo at the engine end of the throttle cables) returning to normal though still unresponsive to throttle input?

It sounds as if your throttle linkage has broken/become disconnected from the carb "plungers" somehow. I would recommend removing the carbs again, to see that the carbs are mechanically working correctly. i.e. carb linkage cable wheel turning spins shaft, shaft actuates levers (in the carb under that top cap casing on the carbs), levers lift throat restrictors, carbs open evenly.

Position the carbs so that you can look through the throats and open/move the linkage by hand to see that all of the carbs throats open up as they should. I imagine potential problems/failures here are what caused whoever to call them a "lost cause."

Because it is your first time at this I am starting way, way basic. If this has already been done, try following the link from the home page "KZ information" to find an article on "carb synchronization." It could be that the carbs are way out of whack compared to each other ( some closed completely, others halway open), but the unresponsiveness of the engine causes me to doubt this.

Regardlessly, you should synch the carbs, once you find out why the engine is unresponsive.

I just rebuilt the carbs on my 77 650 and am now playing with the settings (riding with a screwdriver in my pocket, adjusting them at stop lights and such), I have been having success though. I am not sure as to the similarities between the 650 and the 400, but I would love to help with any of what I have learned recently.

Best of luck and happy fiddling.

Thanks for the info. I will remove the carbs and inspect as you described. Also thanks for the throttle push/pull clarification.

When I got the bike it didnt spark. When I got it to spark, it would only start for a few seconds, then quit. With no experience with carbs, I found a mechanic who unpacked these bikes in the early 70's to early 80's and had experience maintaining Harley's. He got halfway through disassembly and said that there were frozen parts that could not be removed, and that they were "too far gone". I got the carbs back (in pieces) and began to remove everything I could see. The frozen parts were the choke plungers (?) and the slow and starter jets. Also the pin(?) on one of the float jets did not function (I replaced the 2 foat jets). I removed everything I could find, cleaned every part (even using a sewing needle on some of the jets with holes), blew into every piece/hole to make sure the passages were clear. I reassembled according to the manual and reinstalled on the bike. It started. I was very impressed with myself.

Now that I have had time to think about it, the high idle may be due to the idle adjustment, since I set it to where I believe it was set when I got the bike (based on the rust on the screw). This weekend I will dial it down.

Also the air box is not attached. The manual says that an unresonsive engine could be due to a lean mixture. After I inspect the functionality of the carbs, I will make sure they are secured tighhtly to the boots and install an air filter. The manual suggests adjusting the mixture screw to fix the lean condition, but a friend warned against that, as a last resort. What does the board think?

Thanks for the help. I had no idea so much went on inside the carbs. I thought that it began and ended with the cables opening and closing the butterflies.

The push and pull cables may look the same, but they are not. The L shaped metal end that goes to the throttle end of each cable is slightly different to allow them to both be screwed on or off relatively independently of the other. If they were identical it would be a major pain, because they would always be butting together as you tried to install or remove them. This being said is no help of course. The push cable is not necessary at all, just an added safety measure, because we know if the throttle stuck open, with the general public being sue-happy it could be a disaster.

I just replaced both the cables on my bike, the shop catalogue had the same part number for both cables, push and pull. One cable needs to be inserted before the other, and is the closer of the two. The second rides higher, due to the 90 degree bends clashing. This was the setup as I removed it as well. First I tried to put them both on together and had to stop and figure it out.

Mike, I guess that I dont know what "unresponsive to throttle input" implies.
Is there no change at all?
Do you hear a coresponding change in the motor tone?
Like going from "eee" to "ohhh" as the throats open.
Is there just no increase in RPM?
Does it bog?
Is it just really gutless?

Your friends warning to not touch the screws on the carbs is a good one, it is easy to mess those things up. It is good to go to those after you have checked all else first.
But the idle adjustment is different, as it is not a part of the carb itself. It is a part of the linkage ans merely sets the minimum idle speed. Do turn it down. In fact turn it all the way down and see what happens. It is ok to do this while the bike is running.
Now back to the lean condition. Remember those screws that are good to leave alone? Use those to enrichen the mixture. Remember to do exactly to the other carb, what you do to the first. I frequently turn them all the way in again so that I can come out two and a half turns on both of them 'from scratch' each time if you will. That is when I am messing with them as I am now. Find the screw that affects the gas fuel mix to the main jet, and cut the air back/fuel up a little. Whatever it takes, not all carbs are built the same. My carb also has a screw for idle rpm fuel mix.
Give both a twist, quarter turn half turn, whole turn what have you, and test it out. Riding or otherwise. twist em again and see if it improves or not. take em out until the bike runs rough and remember where that is. for me it was like 5 turns out. Too rich it might backfire as unburned gas in the exhaust ignites. Too lean usually is accompanied by a slight increase in rpm as the mix gets just right. Just right for an engine under minimal load. Just right at idle is too lean under load, the engine needs more fuel to do work. When it is time try the same on the road. I have been going from stop light to stop light adjusting as needed.
These things are hard to understand at first. I found I just needed to experiment.

Kudos for getting the carbs apart, unstuck, and working smoothly. Be sure that nothing is sticking again.

Keep us posted

Kawasaki part numbers are not the same for the cables and they are different, but if you are buying non-Kawasaki factory parts I wouldn't doubt they would consolidate 15 or 20 Kawasaki cables into one "exact replacement". Exact replacement meaning +/-8" length variance ect.