QuestionI have a 83 Kawasaki gpz 750. sometimes it only runs on 3 cylinders. it usually doesn't run on number 4 but sometimes number 4 runs and another one doesn't. also some times they all run. do you have any clue what this could be.
AnswerStart by giving it a good tune up - new sparkplugs & air filter, adjust valve clearances, check ignition timing, balance carbs (this may or may not be possible if one cylinder isn't running). This probably won't solve the problem but it will eliminate the easy stuff.
Make sure you don't have any air leaks where the carbs connect to the manifolds or to the airbox. Make sure the spark plug wires are all in good condition and the spark plug caps are making good contact with them. Examine the plug caps for any signs of damage or wear and replace them if necessary. If they are the original wires you should consider replacing them at some point because even the best insulation eventually breaks down and you could find ourself stranded far from home in the rain. I once limped home in a downpour on my GL1000 with one cylinder firing. After I replaced the plug wires it never happened again.
Find the section in your shop manual that describes how to check the ignition system and go over it thoroughly.
If all that doesn't fix it you might have to clean your carbs. www.randakks.com has lots of good information about cleaning GoldWing carbs, but the principles are the same.
Some carbs have screens above the float valve seats that can become clogged with debris. If your carbs have removable seats take them out and make sure the flow of fuel isn't restricted by clogged screens.
That's all I can think of right now, but go through your shop manual and see if you see anything else that might make the problem move from one cylinder to another.
If you don't have a shop manual you should get one - your bike is an antique and you will have a hard time finding a shop that will work on it. The sad fact is that a lot of the mechanics working now are too young to remember bikes this old and aren't interested in learning about them so that they can do a proper job since yours may be the only one they see this year. This means that you will have to do most of your own work, and working on a bike without a good shop manual is just not worth the headaches. (My bikes are from the same era - that's why I fix them myself.)
I recommend that you get two manuals - a Factory Shop Manual and a Haynes or Clymer. That way when you don't understand the explanation in one you will probably figure it out when you have read the other too. If you spend some time on Google you might even find a factory manual available for free download.
