Kawasaki KZ750....Need Help!!

[Johnthekawman]

:confused: I am restoring a Kaw Kz750 and have run into a dead end. All is done on the bike BUT, here comes the part where I need someone's input. I'm sure it's something very simple but my frustration has caused it to appear more complicated!! This bike is a Kz750 twin. My problem is that I can't get a good spark to the plugs. The bike will idle with the choke on ONLY. The minute you open the throttle, it dies! I've changed the coils, tried 3 coils that I know work and to no avail. Carbs are rebuilt. Has new points and plugs. Wires are good. Has new battery, new starter selonoid(sp), and wiring harness is just fine. Can anyone help?? What could be the cause? Sure appreciate what you can offer. Thanx

[CB750F]

If it wont run unless the choke is on it sounds like its running lean.When you rebuilt the carbs did you put new jets in? If you didnt pull the pilot jet back out and you should see a couple little holes running up the side of the jet tube. If they are plugged up you wont get near enough fuel at idle. Same for the mains there are little holes running up the tube. It doesnt take much for them to get clogged.

As for spark it sounds like you tried everything with new points and different sets of coils.Did you also put new condensers in too? Thats the only thing I can think of that you havent eliminated.

[Johnthekawman]

Thank you for replying. I have not replaced the condensors. This is my story so far: I have cleaned the carbs 3X's. I ate my spaghetti out of one of the bowls!! LOL :) Anyway, there is no gummy residue at all. If the screw out of the bottom of the float bowl and gas flows freely, then it's not starving for fuel, right? I soaked the carbs overnight in carb cleaner so I know they are clean. Now, as far as checking to see if jets are the correct ones, maybe I should try that. I know they are clean because I used canned air on them after cleaning them. I looked in my manual and it says to adjust the pilot screw out 1-1/2 turns but, I can't find the pilot screws!! I can find where they are suppose to be but there is a plug there. If I pop out the plug and there is no screw, then they will leak and I will have to replug the hole again. How can I know if there is a pilot screw without taking out the plug. Also, FYI, it came with those plugs in so I'm just going by what I am finding there. Hope you can follow me so far. I'm ready to kick the bike at this point. It's really driving me nutz!! Thanx for ANY advice!!

[CB750F]

To clean a carb right you got to take it apart. Take both jets out and clean them plus the orafice they go into.The best money to spend is a set of carb kits. I got mine off of www.partsnmore.com (http://www.partsnmore.com) and it wasnt too much money. If I remember right it was under $50 and I got 4 of them. They come with new stock jets and needles and all gaskets. That way there you eliminate a good bit of things that can be wrong (clogged jets,worn needles, some jackass drilling out the stock jets ect.).

There should be mixture screws towards the front of the carb.Some late 70's bikes had them hid under plugs but your going to want to make sure first.Do yourself another favor and pick up a shop manual for your bike. One of the Haynes or Clymer ones would work out ok.

Sounds to me like your getting plenty of fuel to the carb bowls but it isn't getting into the motor.

[mute]

Another culprit could be an air leak around one of the rubber boots either between the carbs and motor or carbs and air filter/box.. will make the bike run very lean, lean enough to not run..

[CB750F]

Another culprit could be an air leak around one of the rubber boots either between the carbs and motor or carbs and air filter/box.. will make the bike run very lean, lean enough to not run..

Yeah forgot about that. A good way to check for a vacuum leak is to spray non flamable carb cleaner around where you think the problem is. It will temporarily seal the leak if its not huge and the RPM should change when you hit the leak. Don't use starting fluid,that don't work too good. Trust me on the starting fluid one.