KZ1000 Cylinder Head Swapping

Well, the rubber damping ring on the cam chain roller between the two cams disintegrated on me. Cams were flopping around timing-wise and I smacked a valve on a 9k RPM upshift. Oh well. So I have to pull the head.

I bought a whole head on eBay because as long as I'm in there I might as well replace the whole head (broken fins, messed up exhaust stud bosses, ported out wayyyy too big by the previous owner, leaking oil due to gasket surfaces being pried apart by the PO, etc.)

So here's the question: It's a '79 head and everything seems to be the same except that there are 4 ports on the exhaust side of the head, on the spark plug side of the camshaft housing that don't match up with my '77 cam cover and gasket.

I assume these are for emissions/air injection/crankcase ventilation or something else equally worthless. I can't see where they go. Can I drill, tap, and countersink a hole square to the gasket surface into these and then plug them with a small threaded plug, or am I just wasting time?

-Dave

yes your wasting your time you must send me that head immeditly. actually the head once those holes are filled is a direct bolt on and you can even use your original valve cover.

if you use the camshafts from the 79 head make sure you use the camsprockets from the 77 or you are going to have a hell of a time getting your cams right,if you can even get the chain to go on! stock 77 crankshaft has 15 teeth on timing chain sprocket and 30 teeth on each cam sprocket,if the head came off of a 79 mkII motor it had 16 teeth on crank and 32 on cam sprockets.79 ltd motor still had small crank i believe ,so make sure to count teeth on cam gears!

Thanks for the info!

I'm just going to swap over the Andrews 2x cams and add a set of APE cam sprockets appropriate to the 15t crank I have , so I expect no problems there. Should I replace cam bearings? Use the ones from the original head or the new head?

-Dave

Also. I repaired the cam idler sprocket by machining an aluminum sleeve down on the lathe to fit where the rubber was. It's a tight fit (had to use a hydraulic press to fit the sprocket/sleeve/bearing assembly together). It seems real solid and the bike ran with it no problem the 10 miles home (with the bent valve) from the shop. Is there any problem with not having a rubber damped sprocket, or do I need to spring the money for a replacement.

-Dave

the rubber would make life a little easier on the chain i would think

I finally have th eBay head apart. Everything looks really good and fresh - valves, guides, seats, bearings, and so on (a few threads need helicoiling - no problem).

Going back to the question about plugging the emissions ports - does it make a difference if I plug them at the top (easy) or plug them at the hole in the exhaust port (hard). Thats a pretty big hole in the exhaust port! Is this going to disrupt exhaust flow?

I am planning to mildly port this head (increase bowl volume, blend and smooth casting flaws, blend rear seat ridges, port match).

Once again, am I wasting time, or do I simply have a nice clean, usable '79 head to sell back on eBay?

Also, any porting tips? I have already read many of the existing posts on the subjects and it seems pretty cut-and-dried. Any specific points?

Am I asking enough questions?

-Dave

plug the top of head,then you can use old style valve cover.as far as porting tips ive done a few of my own over the years.the best porting tip ive got for ya is box it up and send it to larry cavanaugh or timebomb depending on which end of the world you live! :laugh: its much easier to turn a good head into a 15lb aluminum doorstop than it is to port one the right way,i made a lot of doorstops in my early attempts im here to tell ya! :woohoo: trust me on this one, save your time /money and frustration and just have it done by somebody who does it everyday!

While youre at it look for a Canadian or UK valve cover- no emissions ports and you lose that fugugly US version.If you keep the one you've got you can get port covers from APE and others on here have made their own,if you're handy with machining aluminum.Good luck.

beefsquasher wrote:

I finally have th eBay head apart. Everything looks really good and fresh - valves, guides, seats, bearings, and so on (a few threads need helicoiling - no problem).

Going back to the question about plugging the emissions ports - does it make a difference if I plug them at the top (easy) or plug them at the hole in the exhaust port (hard). Thats a pretty big hole in the exhaust port! Is this going to disrupt exhaust flow?

I am planning to mildly port this head (increase bowl volume, blend and smooth casting flaws, blend rear seat ridges, port match).

Once again, am I wasting time, or do I simply have a nice clean, usable '79 head to sell back on eBay?

Also, any porting tips? I have already read many of the existing posts on the subjects and it seems pretty cut-and-dried. Any specific points?

Am I asking enough questions?

-Dave

Open the throats to 32mm.

When measuring the bowls, take them to 34mm.

Raise the roof 3mm in the guide boss area.

Don't get any low spots in the runners.

Don't make the entrance of the port any larger if you have 26, 28 or 29mm carbs.

Here's how to measure the bowl.

larrycavan wrote:

beefsquasher wrote:

I finally have th eBay head apart. Everything looks really good and fresh - valves, guides, seats, bearings, and so on (a few threads need helicoiling - no problem).

Going back to the question about plugging the emissions ports - does it make a difference if I plug them at the top (easy) or plug them at the hole in the exhaust port (hard). Thats a pretty big hole in the exhaust port! Is this going to disrupt exhaust flow?

I am planning to mildly port this head (increase bowl volume, blend and smooth casting flaws, blend rear seat ridges, port match).

Once again, am I wasting time, or do I simply have a nice clean, usable '79 head to sell back on eBay?

Also, any porting tips? I have already read many of the existing posts on the subjects and it seems pretty cut-and-dried. Any specific points?

Am I asking enough questions?

-Dave

Open the throats to 32mm.

When measuring the bowls, take them to 34mm.

Raise the roof 3mm in the guide boss area.

Don't get any low spots in the runners.

Don't make the entrance of the port any larger if you have 26, 28 or 29mm carbs.

Here's how to measure the bowl.

yeah that sounds really simple now dont it? run for your lives boys! :woohoo:

That's good stuff! Sounds like the kind of advice I'm looking for.

So the throat is the area just above the valve seat and the bowl is the area farther up around the valve guide?

I'm running 34mm Mikuni RS carbs, if that makes a difference. I know they're too big, but that's what came on the bike so I'm gonna use them.

I got some heavier springs and am clearancing the cam area so that I can drop in some larger cams when I get some more dough together.

Is is worth it to go larger on the cam than my existing Andrews 2x cams (approx .360 lift) with my current setup?

-Dave