Running on two cylinders

1982 GPZ750

Cylinder #1 and #2 do not fire. All across the head I have 140-150psi, and strong spark. It seems that they're not getting fuel, as I couldn't smell any coming out of the spark plug hole or on the spark plug itself. My carbs are freshly rebuilt, and even so, I went through and cleaned them again. Nothing changed. I tried running the bike without the airbox and spraying carb cleaner into the open carbs and got nothing.

The bike backfires through the carbs occasionally, could this be a timing issue? I checked the timing advancer and it seemed stuck, so I'm currently getting it back up to spec. Should I check the cam timing as well? I just finished a head rebuild so I'm confident that it's all correct, but you never know. Or could this be electrical?

Thank you for the help!

Did you check the fuel heights when you rebuilt the carbs? If the heights aren't correct they could be blocking fuel from entering your carbs

I don't see how it could be a cam timing issue. If it was, all 4 cylinders would have the same problem. Also, I don't think it would be a problem with the ignition system since cylinders 1&4 are on one coil and 2&3 are on the other. If a coil wasn't firing properly it wouldn't affect 1&2. Does you carb rack have 2 fuel supply lines? If so, maybe the line for carbs 1&2 is plugged up. Check the fuel levels as mentioned by nickleo373 using the clear tube method. You may even want to just pull a drain screw on carb 1 or 2 to see if the bowl had sufficient fuel in it. Be careful to catch the fuel in something, and NO SMOKING during this test. Ed

Is it possible you just have the spark plug wires on the wrong plugs?

I was under the impression that each plug fired simultaneously (waste spark). I'll switch them around and see what happens.

Would someone happen to know the stock float height perchance?

As Ed mentioned, one coil fires the # 2 and #3 plugs, while the other coil fires the #1 and #4.

The coil firing #1 and #4 will have a black wire.
The coil firing #2 and #3 will have a green wire.

I don't know where to get a link to the manual for your bike but the float height question was asked on the Kawasaki motorcycles forum.
www.kawasakimotorcycle.org/forum/mechani...-float-question.html

loudhvx wrote: As Ed mentioned, one coil fires the # 2 and #3 plugs, while the other coil fires the #1 and #4.

Right, and #3 and #4 fire beautifully, which leads me to believe that the arrangement isn't an issue. Even so, I'll see what I can do.

I did find the stock float height: 18.6mm and have adjusted each carb as such. None were that far off. So I did a fuel height check immediately afterward and all four carbs seem to have the correct fuel heights.

freakinbike wrote: 1982 GPZ750

Cylinder #1 and #2 do not fire. All across the head I have 140-150psi, and strong spark. It seems that they're not getting fuel, as I couldn't smell any coming out of the spark plug hole or on the spark plug itself. My carbs are freshly rebuilt, and even so, I went through and cleaned them again. Nothing changed. I tried running the bike without the airbox and spraying carb cleaner into the open carbs and got nothing.

The bike backfires through the carbs occasionally....

Which cylinder(s) is/are backfiring through the carbs occasionally?

Has starting fluid spray been tried instead of carb cleaner?

What ignition?
What plug wires?
What spark plugs?

Good Fortune!

Patton wrote:

freakinbike wrote: 1982 GPZ750

Cylinder #1 and #2 do not fire. All across the head I have 140-150psi, and strong spark. It seems that they're not getting fuel, as I couldn't smell any coming out of the spark plug hole or on the spark plug itself. My carbs are freshly rebuilt, and even so, I went through and cleaned them again. Nothing changed. I tried running the bike without the airbox and spraying carb cleaner into the open carbs and got nothing.

The bike backfires through the carbs occasionally....

Which cylinder(s) is/are backfiring through the carbs occasionally?

Has starting fluid spray been tried instead of carb cleaner?

What ignition?
What plug wires?
What spark plugs?

Good Fortune!

Cylinder #1 is the one backfiring through the carb, I believe. I have not tried using starting fluid.

I'm using stock ignition with NGK BSE8 plugs in all four cylinders, Dyna 3.0ohm coils, and 7mm dynatek copper wire.

First do all four spark, or do you get no spark on 1 and 2? If both of them are not sparking then I would suggest you check the spark plug caps and make sure they have not gone south. If they are fine try snipping a small amount off of the cable and then re install the caps.

If on the other hand all 4 are sparking but 1 and 2 are not running then check the carbs for clogs, proper fuel levels, air/vacuum leaks.

gd4now wrote: First do all four spark, or do you get no spark on 1 and 2? If both of them are not sparking then I would suggest you check the spark plug caps and make sure they have not gone south. If they are fine try snipping a small amount off of the cable and then re install the caps.

If on the other hand all 4 are sparking but 1 and 2 are not running then check the carbs for clogs, proper fuel levels, air/vacuum leaks.

Ran through this. I have spark across all four and went through, again, cleaning my carbs. I checked my fuel levels and set them to the stock height and got nothing. Checked vacuum lines and everything is in order. If I deleted my silencer, would that have any positive effects on this situation?