79 kz750 twin, one cylinder not firing

Alright i pulled the perfect functioning motor of my kz750 twin out for the winter to paint the frame and replace a couple things. I put it back in and wired it up, the bike fires right up but it appears that only one cylinder is firing. Here is what I have tried already,
checked for spark had it, just to be thorough put new plugs in. Then i switched the wires coming from coil, same cylinder fires and runs put nothing from the other. I pulled the pods off to make sure they are both getting adequate airflow.

Now when I pull the plug it is wet with gas, and I know that means flooding. But im pullin my hair out wanting to ride. Anyone have advice would be awesome.
Thankscempoint

Hopefully I can learn from this topic, I have the exact same problem, on the exact same bike.

anewmanbp wrote: Alright i pulled the perfect functioning motor of my kz750 twin out for the winter to paint the frame and replace a couple things. I put it back in and wired it up, the bike fires right up but it appears that only one cylinder is firing. Here is what I have tried already,
checked for spark had it, just to be thorough put new plugs in. Then i switched the wires coming from coil, same cylinder fires and runs put nothing from the other. I pulled the pods off to make sure they are both getting adequate airflow.

Now when I pull the plug it is wet with gas, and I know that means flooding. But im pullin my hair out wanting to ride. Anyone have advice would be awesome.
Thankscempoint

My guess is a stuck float in the dead cylinder carb, flooding that cylinder with fuel and drowning the spark.

Seen that one many times.

Alright I will pull the bowl off tomorow and see if the float is stuck. I will report back my findings, thanks

The twin can't fire only one side with a fouled plug on the other, they are wired in series. Oil foul or carbon foul or gas flood one plug and that means they both can't fire.

One side dead is probably a carb not feeding gas, plugged up pilot jet, etc or stuck float as already mentioned. If the carbs sat dry while you worked on the bike, they are probably in need of some work now.

bountyhunter wrote: The twin can't fire only one side with a fouled plug on the other, they are wired in series. Oil foul or carbon foul or gas flood one plug and that means they both can't fire.

One side dead is probably a carb not feeding gas, plugged up pilot jet, etc or stuck float as already mentioned. If the carbs sat dry while you worked on the bike, they are probably in need of some work now.

Not had your coffee yet?

Start here Gasoline test of conductivity
And that's at a mere 10 volts, now imagine the effects of 30,000 volts, even air is a conductor at that voltage.

And, didn't you read my post about my fuel service level experiments? Where I lowered the fuel level in one fuel bowl until that cylinder wouldn't run. And then increased the fuel level 1mm at a time until I got to the point where I was flooding the cylinder with fuel and it wouldn't run again? And I rode the bike each time (on one cylinder sometimes).

From the very first post

Now when I pull the plug it is wet with gas

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So wouldn't you say that cylinder "is" getting gas?

Here is a simple way to show that I am correct. Pull the air box boot off one carb, start the bike and then block the airflow to that carb by placing your hand over the intake while increasing the throttle opening so the good cylinder can pull the dead one along. Totally flood out one cylinder and the bike will keep running.

Like I stated in my original post, seen this happen many times.

And you wouldn't believe the frustration I can cause with a carbon pencil and an ignition system :evil:



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steell wrote:

bountyhunter wrote: The twin can't fire only one side with a fouled plug on the other, they are wired in series. Oil foul or carbon foul or gas flood one plug and that means they both can't fire.

One side dead is probably a carb not feeding gas, plugged up pilot jet, etc or stuck float as already mentioned. If the carbs sat dry while you worked on the bike, they are probably in need of some work now.

Not had your coffee yet?

Start here Gasoline test of conductivity

All I know in life I learned the hard way: a flooded cylinder won't fire. I used to have the standard "overflow" syndrome on my 750 twin where one carb would flood a cylinder with gas and the bike would be DEAD DEAD DEAD (neither cylinder would kick) until I spun the plug out, dried the wet one and waited for the gas in the cylinder to "air out" a while. The inside of the cylinder is loaded with crud which liquid gas floats and then coats the plug with. Never fired on mine.

That's pretty weird, must have had something else going on. Before I gave the 82 KZ1000M to my brother number one carb float would stick and the bike would run on 3 cylinders. I would reach down and tap it with a pocket knife and it would star working and running on all cylinders again (after cleaning out). When you buy old junk bikes like I do, things like this are common.

steell wrote: That's pretty weird, must have had something else going on. Before I gave the 82 KZ1000M to my brother number one carb float would stick and the bike would run on 3 cylinders. I would reach down and tap it with a pocket knife and it would star working and running on all cylinders again (after cleaning out). When you buy old junk bikes like I do, things like this are common.

If the float sticks UP, you get a dead cylinder from no gas and the tap brings it to life. But, I used to leave the petcock in the ON position during the day and turn it off at night. Sometimes I would come out during the day and find the puddle of gas from one of the overflow pipes and the flooded engine would be DEAD. I would have to crank the hell out of it and it would finally fire with a loud BANG backfire then run rough and smooth out after a bit. If I was at home and found it flooded, I would just take the plugs out and clean them. Let the gas clear out and then it would start.

Flooding, is when the engine overloads with fuel, so bad, the spark plugs foul and will not fire.
Liquid fuel conducts electricity so good , it shorts out the spark plugs. So does carbon, conduct better.

fixkick.com/flooding.html

The other stuff I found via Google was forum posts, but all said the same as the above link.

And I explained how to do an experiment to confirm my statement in an earlier post.

I don't know what else I can do to persuade you, so I am dropping it now.


We now return you to your regularly scheduled program


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bountyhunter wrote: The twin can't fire only one side with a fouled plug on the other, they are wired in series. Oil foul or carbon foul or gas flood one plug and that means they both can't fire.

Hi BH,

If a plug is fouled so badly that it won't spark that does not mean that the electricity does not flow. With both plugs in series, one clean plug and one fouled plug, the clean plug will generate a spark and that spark will travel through the carbon build up on the fouled plug to complete the circuit.

Bill

So what does this mean?
I've changed plugs, checked got spark on both, pulled one spark plus lead off, at idle bike still runs, pull the other off, bike died.
Ibefore doing this, I swapped leads a few times, to ensure spark.and too confuse me even more, the left side seems to still not be working, no matter which lead is on it.
when I pulled the lead is right side, it sputtered a bit and died.
Diagnosis would be beneficial here.
Thanks in advance.