TOPIC:

There are 2 small square flats about the size of a postage stamp cast on the cylinder head fin just past the gasket face below the exhaust valves. This skim marker allows a straight edge and feeler guage to test whether a head has been skimmed.

What is the measurement on an unskimmed head? I can't see any reference to this any factory manuals. I'm guessing this will be a standard figure for all kz bikes.

I was googling for an anwser on this but just fund the same question that I asked about 10 years ago...never did get an answer on this.

I've checked my GPz1100 B head, getting 1mm, on a head that seems quite standard (contrary to what PO told me )

I have a stage 3 550 head wthat has been skimmed beyong the marker, although combustion chambers were reprofiled and standard volume). The head is clealy skimmed as without slotted cam sprockets the valve timing is a mile out, and the carb flanges are flattened also.

Knowing what the factory spec for this skim marker clearance would be really helpful, if anyone else has a kz head they can measure? .

Getting 1mm clearance on a GPz110 B head.

Another stage 3 550 head is skimmed below the markers.

Anyone know what the factory clearance is between these markers and the head gasket face on an unskimmed kz gpz head is?

It may take me a while to dig out the two 550 heads I have bare, but i'll try to measure them when I get a chance. It may be a few days.

Thanks Lou, knowing this measurement will tell if the head has been skimmed and to what extent.

Getting this factory spec max number will come from an unskimmed head.

The knowledge is out there, it just seems to be a 'trade secret'.

what makes you believe this to be an actual reference point that is supposed to be the same across the board?

just curious as you are the only one i've ever heard mention this.

leon

531blackbanshee wrote: what makes you believe this to be an actual reference point that is supposed to be the same across the board?

just curious as you are the only one i've ever heard mention this.

leon

I don't. just a guess it might be a standard figure, even if only across the aircooled kz fours,

Getting some numbers back here from a few different models, particularly if the head is NOS or known to be unskimmed, would be interesting.

Apart from wonky advanced timing and the marks not lining up, and shaved down carb bolt hole castings or measuring combustion chamber cc against factory spec, how else does one know if the head has been skimmed? and I'm wondering if a very light skim would be even apparent by the above means.

Shaving the head should retard the timing.

I have one motor which is probably shaved. The valve timing is slightly retarded, the compression test shows over 200 psi, the motor knocks much more often than my other Gpz's, it likes octane boost, and I think I occasionally hear what may sound like the valves are just nicking the pistons when the oil pressure is low and the motor is hot, just after restarting. That motor should be coming out soon. I've been waiting 10 years for it to finally die.

Doh! retards timing , of course Thanks Lou.

Both my 550 heads are shaved, one to well below the marker.

Maybe if you dial the valve timing in, and you know the combustion chamber volume, so CR can be worked out, maybe how much was skimmed from the head since new is irrelevant...just i'd like to know.

New one on me.
Steve

Tyrell Corp wrote:

531blackbanshee wrote: what makes you believe this to be an actual reference point that is supposed to be the same across the board?

just curious as you are the only one i've ever heard mention this.

leon

I don't. just a guess it might be a standard figure, even if only across the aircooled kz fours,

Getting some numbers back here from a few different models, particularly if the head is NOS or known to be unskimmed, would be interesting.

Apart from wonky advanced timing and the marks not lining up, and shaved down carb bolt hole castings or measuring combustion chamber cc against factory spec, how else does one know if the head has been skimmed? and I'm wondering if a very light skim would be even apparent by the above means.

it will be interesting to see what you come up with.
i've never known a good way to tell if a head had been shaved.

leon

I am using sae feelers, so the metric increments are not even values.

On one head the fattest gauge that would slip in, without lifting the straight edge was 0.41 mm. This head is pretty clean, but was re-painted at some point, and is the one in the photos I'm including. I'm not certain what prep was done, and how thick the paint is, so it might not be representative of a factory-fresh head.

On another head, the fattest was 0.46mm, but this head was pretty dirty, and the paint was missing from the pads. The pads showed some corrosion, which I scraped off before measuring.

I believe these heads were never skimmed.