Kawasaki Zephyr 550 will only start with choke

[garacs]

So I made a small video of the engine starting when already hot. Cold, it needed the choke...

Here's the link

https://youtu.be/_kO2IB55lcg?si=hS3BcNRmwZSaimAY

The response to the gas is so slow I can take a coffee before it gets back to idle ...

Is this a definite sign that I need to reclean the carbs?
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Working on it: Kawasaki Zephyr 550B 1991

[Nobby the Bastard]

That soounds like an air leak.

Possibly something sticking open.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Robby]

Yes, inlet air leak will do that.

[garacs]

[garacs]

So I disassembled again for the fourth time carb 1.... This is the gasket on the idle screw
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Working on it: Kawasaki Zephyr 550B 1991

[garacs]

no idea why or how that happened, all gaskets were replaced.
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Working on it: Kawasaki Zephyr 550B 1991

[garacs]

So I reinstalled the carbs, started the motor: only cylinders 2 and 4 were working... Which is weird, since it means both coils were not working properly. Switching them, now I had cylinder 1 not working again, all other cylinders working...

So I took out the coils and checked again with a multimeter the coils, the wires, the plugs. All specs within range. I cut the tip on both ends of all the coil wires to give fresh metal for the plugs to bite into.

I then replaced all the sparkplugs, with the ones the bike had when I bought it: now the engine started with all 4 cylinders!

But... since i was doing everything without the fuel tank attached (using the fuel inside the carbs bowls) I had to turn off the motor. When I restarted it, cylinder 3 was not working anymore....

Removed the carbs, cleaned again all jets (they were not clogged, but just in case and before you guys tell me to clean them anyway...) reinstalled all but no joy...

The engine starts even without choke (finally) but only on 3 cylinders.

If there is an air leak, I have no idea where it could be. Ah in the meantime I fitted new copper gaskets on the exhaust manifolds.

I am honestly thinking to replace the coils, wires and plugs...
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Working on it: Kawasaki Zephyr 550B 1991

[A100man]

[garacs]

[A100man]

[WD Forte]

The old CX's had long reach plug caps with 5K resistors in them which often rotted out.
Some folk used to fit brass blanks in them but
I always swapped them out for non resistor types which were cheaper and never gave any problems.
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bikers smell of wee

[garacs]

[garacs]

[garacs]

Here I am, back tinkering with my Zephyr after a small pause due to personal stuff getting in the way...

So I did not buy the coils as I was hoping to do. Yet today I brought it out again just to check... and it did not start.

I brought it back in removed the carbs, replaced the jets and gaskets with new ones I received in the meantime, and after a bath in ultrasonic, I reassembled everything back together.

Brought the bike out, pulled the choked and after some turns it started, but again, only runs with choke.

I also noticed now it was only running on cylinders 1 and 2.

So I did something you are not supposed to do... I unplugged the sparkplugs 3 and 4 with the engine running.

RPMs got higher so I "calmed" them down removing the choke, and the cylinders were happily running. As soon as I replugged the sparkplugs for cylinders 3 and 4 these also started to work, but really roughly and I had to adjust the idle a bit. Yet all 4 cylinders were working!!!

So I did the stpid thing, and shut the motor off... And restarting it, only ran on cylinders 1 and 2.

I unplugged them, and started the motor again, only having cylinders 3 and 4 plugged, and it ran only with choke.

So reassuming:

1 and 2 work without choke and with 2 and 4 unplugged.
3 and 4 work only with choke and 1 and 2 unplugged.

I swapped the coils around, same results.

Can someone let me know what the heck is happening????
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Working on it: Kawasaki Zephyr 550B 1991

[jaffa90]

Strange one this, one coil serves 1+4 cyl and the other 2+3 cyl.
Q, what input voltage readings have you got to the coils when swapping / tinkering about?

[garacs]

[garacs]

I did not measure the arcing distance, but each spark plug had a bright blue-purple strong spark, by eye-measure linger than 5mm.

One thing I noticed, when the caps were unplugged they were still arcing to the metal parts of the motor. Also touching them I got small shocks. Is this a sign they are not properly isolated? Could this be part of the issue?
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Working on it: Kawasaki Zephyr 550B 1991

[garacs]

[garacs]

Since I found out I have much probably a vacuum leak on both sides of the carbs, would using RTV on the mating surfaces be a possible solution? At least temporarily?

The rubber of the air box boots is still soft for the most part, but on cylinder 4 is harder than the others. Plus, the spring on the boot used to secure them on the carbs is quite old... So I guess it is not as tight as it is supposed to be.
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Working on it: Kawasaki Zephyr 550B 1991

[garacs]

On the other side of the carbs, I cleaned the mating surfaces of the intake manifolds. In the pic, on the left how they were, on the right the first one I cleaned and sanded down with 400 - 800 grit. Oring was still perfectly round and soft, no damage, so I reused it (it was probably replaced right before "parking" the bike for years...)

I also cleaned the mating face on the cylinders.
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Working on it: Kawasaki Zephyr 550B 1991

[garacs]

Another picture of the manifolds back in place
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Working on it: Kawasaki Zephyr 550B 1991

[garacs]

Here the manifold before and after
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Working on it: Kawasaki Zephyr 550B 1991

[garacs]

And the saga continues...

After buying new spark plus, I also received 2 "new" (used but said to be in good working condition) coils.

So I put all together, after testing the coils, which had values a bit higher than the ones they are replacing, but still within the limits that are set on the manual.

Yet, after trying to fire the motor up, even if there was a change, I still am out of luck. Now onnly cylinders 1 and 4 work (left coil), while 2-3 don't (right coil).

So I replaced the "new" coil with the old one: same result.

I removed the boots and the spark plugs, and noticed the 2-3 ones were looser than 1-4. Yet I checked the condition and spark...
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Working on it: Kawasaki Zephyr 550B 1991

[garacs]

So here the pics I took, First Spark plug for cylinder 1
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Working on it: Kawasaki Zephyr 550B 1991

[garacs]

Spark plug cylinder 2
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Working on it: Kawasaki Zephyr 550B 1991