Z1000mk2 Exhaust port damage around valve guide

Hi!

I just bought my first Z1000 last autumn, it's a 1980 MK2 and I was pretty excited about it, as I've been wanting one since I saw Mad Max (of course)

Anyways, it smoked as hell when started, whitish smoke, but setteled down when warm so I figured there must be some leakage around valve seals or a problem with rings. I did a compression test and cylinder#1 showed lower compression (around 60) and others were around 120. I squirted some oil thru the sparkplug hole and compression on cylinder#1 rose up to about 100-110. So I figured it must be the rings. At this point the installed Boyer Ignition unit melted while on a ride so I put bike to garage and decided to fix electrical gremlins for good and pull of the top end.

I pulled off the top and saw that cylinders, pistons and rings were actually in really good condition so I don't know why oil test showed ring problem. Valve lifter of cylinder#1 was a bit stuck, other ones lifted out no problem. I found that the previous owner had installed actually a big bore kit of 1075cc and one of my questions is that how can i identify what kit it is and how to get new rings? Rings seemed weird, top and second ring are identical in every way, thickness and shape and all. They're about 0,74mm thick. All rings moved freely and there was no seizing. I have pretty bad pics of the pistons but I'll include them if you guys can identify what I got. It looks like Wiseco kit, but ring thickness doesn't match. Piston diameter is 72mm and they have these thin grooves round the crown area.

The more serious thing I noticed was, that the cylinderhead had some damage in the exhaust port of cylinder #4. This cylinder had good compression though but I wanna ask you guys how serious this is? Do I need a new head or as this worked before, can I go with it? I'll include a pic of it below. The damage is around the valve guide area, some of the casting has broken off.

All combustion chambers were a bit sooty with carbon and exhaust ports were very thick with it. Carburettors were jetted standard but bike had Vance&Hines performance exhaust and open filter pods so it was running very lean and it gave sever kickback on the kickstarter so I guess it was also timed wrong.

So, any ideas where to go with it now? I have carbs cleaned and rebuild kits ready but I want to know what to do with the cylinderhead? Thanks in advance!

-Sami

That "damage" won't do any harm.
It's common.
Most of that disappears when they get flowed/ported anyway.
Just leave it alone if the guide isn't loose.
Pistons look to be 1075cc wiseco or mtc. (usually Wiseco with circlips, MTC with Teflon buttons)
Around 10.25 to 1 compression.
Everything you describe about them is correct.
Stamp on top of piston - XC or XA etc denotes the type of rings used when re-ordering. XA are the older type most likely yours are XC if it's a recent job.
Top ring is usually chrome , second ring plain cast but same thickness.
There is a small mark on one side of the two top rings which should be installed facing UP.
Oil rings go either way.

Thanks for clearing that up! I was a bit uncertain although it looked like the head had been put together before knowing that the damage is in there, but as I have no experience on these bikes I wanted to be certain.

I think lapping the valves properly and setting valve clearances will get me going, maybe those new piston rings too. Old rings look undamaged so I'm not sure will i even replace them. Something funky was happening on the cylinder #1 though, because it had so low compression. I filled combustion chambers with brake cleaner and all other chambers stayed leveled but #1 dropped about a third very quickly, so those valves definitely weren't seating ok.

Is smoke on a startup always sign of bad valve seals?

Valve guide seals and rings. Check the guides for rock and bores for issues.
Steve

Somebody either slipped a differant crank in a mkII motor or youve got an older engine in your bike.

Hmm what do you mean, how can you tell it's different crank?

The alternator cover is from a early model.
Steve

Ahh ok Yeah I haven't done much research on these, I ran the engine and frame numbers when i got it and as far as i can remember, i think they matched to -79 or -80 mk2. It seems also that this bike has quite colorful history, coming to Finland originally from Germany i think, and including one of the previous owners presumably killed by it, so I wouldn't be surprised if I found something weird about it

I see cracks under broken off piece. Clean the place with drimel wire brush and take high resolution pictures.
If I am right about cracks, you need another head or to weld this one.

Might have to be welded and machined for a new guide. That's kinda pushing it if that's another crack.
Steve.

That's probably just carbon deposits 'cos my cleanup wasn't very thorough and pic is bad. I didn't see any other cracks in there while I inspected it, but I'll have a better look at it tomorrow. Thanks for noticing!

They have been known to grind off some of the guide and around it in the porting process. If there's no crack then you should be Ok. Kinda gives me the Willies thinking on riding a dead man's bike though.
Steve