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Discussion Starter · #1 ·
I have a 2006 Kawasaki ninja ZX6R that I just performed a 15000 mile valve adjustment on. I Decided to Perform a compression test to double check the work . Cylinder one is reading about 60 psi although it strangely read 130 PSI (prior to cleaning the carbon off the backside of the valves after completing the valve adjustment as well) All other cylinders have at least 180 psi after 10 cranks completely cold. The only issue is number 1 and I can clearly see the compression leaking past the intake valves via fluid placed on the backside of the valves. A wet test yielded thre same 60 psi results. Intake valves on cylinder 2 and 3 were completely clear of carbon but four did have a minor amount of carbon that was present. The spark plugs all looked unremarkable as well.

I don't know if this condition was present prior to the adjustment as I had not performed a compression test beforehand and it is a new bike to me with a personal 1500 max miles of riding. The valve train was a little noisy when cold and I did notice a minor amount of vibration but no other symptoms at all.

There was nothing remarkable about any of the clearance readings prior to the adjustment but a few valves were below spec. I decided to bump all of the shims toward the top end of spec as I had to remove the cams either way. I have checked over and over and the timing looks to be exactly as it should . The marks on the camshafts are flush with the head and the crank sprocket is at top dead center 4 cylinder 1 which I have verified visually with a straw in the cylinder.

The only issues I can think of are that I had turned the engine by hand 360 degrees after having removed the tensioner because I was at the wrong TDC for the cams according to the pictures in the Haynes manual, however the chain remained taught and I didn't notice any jumping of the cam position or sensation of interference in the engine. Secondly, after looking at the bucket on the very first intake valve (far bottom left) it looks to have a bit of a thin brown film atop it while all others are clean and shiny. Likely nothing important but I noticed it. Lastly, once again, I obtained a far higher reading on compression (130 psi) prior to soaking/cleaning the valves and didn't change or adjust anything else at all before it finally reading 60 psi now.

I am not sure what to do from here and I am afraid to try to start it in order to obtain a warm compression test and I also don't want to pull the head before exhausting all other options...
 

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Do you mean you cleaned the carbon off the seating surface of the valves? How did you go about doing it?
 

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Do you mean you cleaned the carbon off the seating surface of the valves? How did you go about doing it?
Yes. Seating surface, or did you pull the valve and clean the carbon off the back side. Regardless, you have a 'leak down'. Is the edge of the valve chipped? Is there a piece of carbon between the valve and the seat? Is the seat chipped? Did you lap the valve on reassembly? Is the valve flat to the seating area, or is it sticking up a little bit. Is it shimmed so high that the valve is not closing all the way?

And finally, you sure it's not a broken ring?

I'm not a mechanic, so don't take my suggestions as gospel. I'm sure a real bike mechanic will be along shortly.
 

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Discussion Starter · #4 ·
I cleaned the back side of the valve with the head installed (through the runners).

I believe the issue is now solved. I have 180 psi after 10 cranks just like the other 3 cylinders. The compression tester hose wasn't threaded fully into the spark plug seat????? I had a similar issue with removing the spark plug, it threaded out but then just spun as the sticker on the socket rubbed off into the hole for the plug and perhaps gummed up between the socket and wall. Maybe it also fell into the threads??? I noticed that upon achieving some compression while testing, the hose was able to be tightened more and never seems to allow for you to over tighten it. I tested another cylinder and the hose acted similarly after fully tightening eventually.... (Can be spun clockwise without it gaining further torque.)

I guess that the intake valves were pulling vacuum as the compression leaked out through the spark plug threads??? Any further ideas?
 

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Usually leaks at the plug holes are pretty noisy - you can hear the air escaping there pretty easily.

Either way, glad you solved your issue. Personally, my money is on a piece of gunk on the valve seat.
 
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Discussion Starter · #6 ·
The leak was quite audible While cranking with the starter. It just seemed like it was solely the intake valves leaking compression and perhaps they actually were because the chamber was not sealed, therefore creating an environment in which the valve and seat were not pressurized together under the compression stroke. Maybe I do still have a very small leak due to carbon build-up and I will be sure to do all that I can to clean the valves and seats. I suppose that all is well now and I can thank this small stupid issue for causing me to quadruple check my work. I likely won't need to adjust any valves 15,000 miles from now as I bumped all shims toward the top end of clearance and all the cam lobes etc are within spec with minimal wear.
 
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