Head replacement - 75 z900 to kz1000

Hey all,
I am taking the bike into a local machine shop to have my head replaced due to damage by PO.
I am going to get a kz1000 head. The shop owner says they are a match.
My question is this: I do not know what else the PO has done to the internals of my engine. What should I ask the shop to do while in there?
So far I have come up with doing the head swap, checking valve clearance, checking cams, checking timing, and then having him tune the bike after everything is back together.
I am thinking of getting a quote on replacing/oversizing the pistons with a big bore kit.
What else should I be thinking ?

Hi Conspiracy - It's tough to give comprehensive feedback without knowing 1) exactly what damage the PO did and if that damage is confined to the head only; 2) how many miles (or hours) are on your engine and what the compression/state of wear is or was when it was damaged; 3) what you want to do with your bike (restore it to its original specs, modify it slightly, or do a major rework of the engine for large power gains); and 4) how much money you're willing to spend. WIthout knowing any of the foregoing, you risk spending a bunch of money on (or doing a lot of) unnecessary work or work from which you won't benefit. For example, if you're going to have any work done below the cylinder head (e.g., new piston rings) do it when you have the head replaced. The reason is that piston/cylinder work requires removal of both the head and cylinder block, followed by break-in and tuning. If you replace only the head now, but then a week or month later decide you want to put in new rings, you'll have to pay twice to have the engine disassembled (head and block removed, etc.).

That said, here are three observations about engine work on older Kawasakis you might consider:
1) Be careful when replacing a KZ900 head with a head from a KZ1000. It may not be a simple "plug and play" matter, as you can't determine compatibility by only looking at the stud hole alignment; just because it will bolt to your 900 block does not mean it's a match. Your machinist needs to be well versed in, or willing to research or accept information about putting a 1000 head on an older 900 block. It's not rocket surgery by any means, but there are not-so-obvious pitfalls like: (a) You will need to ensure the new head's cam gears (including idler) are compatible with your existing cam chain in terms of length and type. (Or, will it accept your old cams, and are the bearing clearances all correct?) (b) You should also check the condition and status of the cam chain, cam chain tensioner, the plastic cam chain guides, and the rubber dampers under the idler gear tower. [Go look at the parts on offer at the APE race parts site and you'll get the idea. Also, read their tech page about the differences between early and later 1000 cc heads. While on the APE site, buy an APE manual cam chain tensioner - it is widely accepted as one of if not the best, and an important upgrade over the stock version.] (c) If you can't swap your cams over to the new head, you will also need to determine if the new cam specs (timing, duration, etc.) are the same or are at least compatible with your 900 setup, not only for valve-piston and valve-valve clearance issues, but also simply for operability/tuneability issues. (d) There are other items I'm probably forgetting, sorry. The point is, be careful and check everything first. You do not want to miss something, pay to have a bunch of work done, only to have the engine eat itself the first time you start it, or, worse, while you're going around a curve at 70 mph.

2) Even if every other part on the engine is brand new, keep in mind you will never be able to tune it or get it to run correctly or efficiently if you have improperly adjusted valves or valves that wont seal. So, do not put a head on your bike unless the valves (and valve seats) are in tip top shape, along with the springs, guides, and stem seals. When in doubt, get a proper 3 angle valve job before installing the head. It only cost about $200 (unless you need a lot of valvetrain parts), and your machinist should tell you if one or more valves is bent, out of round, has a bad guide, seat, spring, or seal, or otherwise needs replacement before completing the job.

3) You can't make engine improvements in isolation - like just installing larger pistons - or you will at best not realize the full benefit of each change or at worst you will have an engine that runs badly or not at all. For example, let's say your machinist finds a damaged piston or badly scored cylinder walls when he/she opens up your KZ's engine to install your 1000 head. So, you decide that while it's disassembled you'll have them bore and sleeve your cylinder block and install 1200cc pistons. After all, if you need to rework the cylinders/pistons, might as well put in something better, right? The problem is, to realize the full benefit of this increase in displacement, you will also need to port the head, install bigger cams and carburetors, and likely install bigger valves (in addition to ensuring a variety of other details are within specification). A relatively large increase in displacement (the difference in cylinder volume between piston BDC and TDC) means more air is being pumped through the cylinders. However, unless you make corresponding changes to the parts that let air and fuel into and out of the head (the intake and exhaust ports, valves, carbs, etc.), you're not going to get everything you can out of those new, bigger pistons. It would be like getting an extra pair of lungs without increasing the size of your mouth and nose.

Finally, I would encourage you to get a Clymer or factory repair manual for your bike if you don't already have one. Assuming you have a basic set of hand tools, I would also encourage you to invest in the following instruments: an outside 1" micrometer, inside/outside 6" or larger dial or digital caliper, 1" dial indicator and magnetic stand, 6" rule, set of standard or metric feeler gauges, a heavy (1/4" thick) straight edge about 18" long, and an assortment of Plastigauge strips. You don't need anything expensive, import tools are fine. Look on Amazon or Victor Machinery Exchange. For a low cost straight edge, find a machinist's supplier (I use Victor) and order an 18" length of 1/4" thick by 1" wide precision ground oil-hardening tool steel - it will be plenty flat and straight for your purposes. With these items, and a little research and self education (including the relevant sections of your repair manual), you can properly check out a large variety of engine parts, including whether a head is warped, if valves or cams are bent or worn too much, if valve springs are bad, if rod or other bearing clearances are excessive, etc. You can also check non-engine parts like brake rotor thickness, wheel runout, chain stretch, the list goes on and on. You can save a bunch of money and time doing work yourself, even if it's only diagnosis or evaluating used parts. It's hard to beat the certainty that comes with doing a job yourself and knowing it's right.