Crap!!! Valves?

Yeah, I guess I can block the head well up and off my bench and install the intake cam with that lobe up and away. Rotating the cam like this is a bugger, as you probably know.
I guess I could also pull the valves out of the other three to make it easier.

When I had the head done last spring, they said there were two bent exhaust valves and one intake was a little tweaked. So I had all of the bad ones replaced.
But this head is not the original head off my 77' KZ1000A,

Bent valves are pretty rare, these machines as stock have quite generous clearances allowing them to be thrashed to the redline and beyond. High lift cams, big valves , skimmed heads and domed pistons can reduce this valve/valve and valve/piston clearance beyond safe limits if not assembled right.

I'm puzzled on this as there are no witness marks but a bent valve - I'm wondering if the head has been skimmed more than you think, thus reducing the clearances and altering the valve timing. A heavily skimmed head makes quite a difference to valve timing. Do your cam setting marks line up level with the head?

Even if running open velocity stacks with no filters , a stone being swallowed would show damage elsewhere I think. It has been known for the under bucket shims to displace - perhaps explaining the increases clearance, but it is very rare. The earlier kz900 shim over bucket design was modified to shim iunder bucker for this reason.

p.s. the later zx750 unitrack "GPz750" 'bathtub' head has different cams with IIRC a base circle skim for 0.5mm more lift...check out the combustion chambers. The later 1100 heads had a different valve angle.

If it is a later model GPz head maybe your deeper wiseco valve pockets allowed this to run at a tight clearance, wheras a stock piston wouldn't.

Still doesn't explain the no apparent damage anywhere else apart from the valve. :S

I suspect the valve was marginal to begin with and warped. The jetting. cold then hot aggravated it. I ran 125 mains in my 28's but had to go 2.5 needle seats so I wouldn't run out of fuel at extended WOT.
Steve

Tyrell Corp wrote: When I had the head done last spring, they said there were two bent exhaust valves and one intake was a little tweaked. So I had all of the bad ones replaced.
But this head is not the original head off my 77' KZ1000A,

Bent valves are pretty rare, these machines as stock have quite generous clearances allowing them to be thrashed to the redline and beyond. High lift cams, big valves , skimmed heads and domed pistons can reduce this valve/valve and valve/piston clearance beyond safe limits if not assembled right.

I'm puzzled on this as there are no witness marks but a bent valve - I'm wondering if the head has been skimmed more than you think, thus reducing the clearances and altering the valve timing. A heavily skimmed head makes quite a difference to valve timing. Do your cam setting marks line up level with the head?

Even if running open velocity stacks with no filters , a stone being swallowed would show damage elsewhere I think. It has been known for the under bucket shims to displace - perhaps explaining the increases clearance, but it is very rare. The earlier kz900 shim over bucket design was modified to shim iunder bucker for this reason.

My cam marks are "fairly" close for a 42,000 mile cam chain and sprockets.
At least within a few degrees of rotation with respect to the thickness of the cam cover gasket.... with the FSM setup.
The invoice from the machine shop says .012" milled to flatten slight warp in head.
That's all it says about milling.
Now, was the head milled once before I bought the thing many years ago?
S**T the bed!! I don't know and never even thought about that.
I did not check clearance of valve head to piston and the stock Wiseco1075 pistons are fly cut pretty well so I assumed there would be plenty of space. I probably should have dry fit it with some clay.
I'll go back out and look very closely with that LED flashlight but at first glance, I could see no marks on the thin film of carbon on the piston crown in the fly cut area.
I'm at a 98% complete loss. Leaving 2% for a senior moment. At 65 yrs old... I'm entitled.
I've adjusted shims in these things dozens of times, over my life for friends and myself...and sure don't want to think I might have screwed something up and shot myself in the foot
I'm happy I just happen to have some extra NOS KZ1000 valves laying around here and the lapping of a new one gave me a very nice FSM margin and what appears to be a pretty good "static" seal with very thin lacquer thinner like this ....actually I tried spraying carb cleaner into the valve pocket from the intake port side too.... no seeps or weeps.
Maybe I dodged a bullet this time.

There's lots of room on a stock engine. The pistons are made for no mods to be made while installing them.
Steve

My cam marks are "fairly" close for a 42,000 mile cam chain and sprockets.
At least within a few degrees of rotation with respect to the thickness of the cam cover gasket.... with the FSM setup.

My bikes are that sort of mileage plus - it should line up precisely, a few degrees is a long way out. You have the correct number of chain links between the marks? You can fix this by dialing in with slotted cam sprockets or maybe a fatter base gasket.

I'm trying to work out why you are getting through valves on a mild tuned bike with extra valve pockets that isn't being ragged to death, something wrong here.

I'd work it out before using precious NOS valves and being here again in a few months. Maybe check the valve spring tension too.

New springs are a good idea.
Steve